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PHYSICS (580 journals)

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Journal Cover Physics and Chemistry of the Earth, Parts A/B/C
  [SJR: 0.611]   [H-I: 26]   [5 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1474-7065
   Published by Elsevier Homepage  [3039 journals]
  • Profiles of innovators in a semi-arid smallholder agricultural environment
           in south west Zimbabwe
    • Abstract: Publication date: Available online 21 September 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Eness P. Mutsvangwa-Sammie, Emmanuel Manzungu, Shephard Siziba
      Innovations are regarded as critical to improving the efficiency, productivity and effectiveness of African agriculture. However, few efforts have been directed at understanding ‘agricultural innovators’, especially among smallholder farmers in sub-Saharan Africa who face low agricultural productivity and widespread food insecurity. This paper investigates the profile of innovators from a local perspective in a semi-arid smallholder farming area in south-west Zimbabwe. The paper is based on data collected from key informant interviews and a household questionnaire survey administered to 239 households from Gwanda and Insiza districts between 2013 and 2014. Qualities or attributes of an innovator (which constitute the profile of an innovator) identified by key informants included: resource endowment; social networks; education; and enthusiasm (passionate and hardworking). The attributes were used in a logit regression model to estimate the probability of the 239 households exhibiting the attributes of an innovator. Social networks and resource endowment, as depicted by amount of land cultivated, were found to significantly influence the probability of an individual being an innovator. Interestingly, the common attributes of education or belonging to an innovation platform used by extension and development agents, were found not to influence the probability of one being an innovator. The paper concludes that understanding local perceptions of innovators, which is based on appreciation of the socio-economic and biophysical circumstances, should be used to identify a ‘basket’ of context specific innovations that have potential to address the diverse needs of rural households farming households.

      PubDate: 2016-09-26T00:50:58Z
       
  • 3rd International Conference on Ecohydrology, Soil and Climate Change,
           EcoHCC'14
    • Abstract: Publication date: August 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 94
      Author(s): Cristina Andrade, Samantha Hughes, João A. Santos


      PubDate: 2016-09-21T00:30:57Z
       
  • Determination of background concentrations of hydrochemical parameters and
           water quality assessment in the Akhuryan River Basin (Armenia)
    • Abstract: Publication date: August 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 94
      Author(s): Hovhannisyan Arpine, Shahnazaryan Gayane
      The determination of background values of hydrochemical parameters, to distinguish between natural concentration and anthropogenically-influenced concentrations, is highly relevant. In presented study, to estimate the background values of hydrochemical parameters in Akhuryan River Basin, log-normal probability functions on the hydrochemical parameters concentrations was applied. The study is carried out on the basis of hydrochemical data of surface water quality monitoring for the period of 2010–2013. This study highlights the usefulness of application of site-specific background concentrations for the evaluation, interpretation of surface water quality and for determination of pollution sources.

      PubDate: 2016-09-21T00:30:57Z
       
  • Nanosized iron based permeable reactive barriers for nitrate removal
           – Systematic review
    • Abstract: Publication date: August 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 94
      Author(s): Rui Araújo, Ana C. Meira Castro, João Santos Baptista, António Fiúza
      It is unquestionable that an effective decision concerning the usage of a certain environmental clean-up technology should be conveniently supported. Significant amount of scientific work focussing on the reduction of nitrate concentration in drinking water by both metallic iron and nanomaterials and their usage in permeable reactive barriers has been worldwide published over the last two decades. This work aims to present in a systematic review of the most relevant research done on the removal of nitrate from groundwater using nanosized iron based permeable reactive barriers. The research was based on scientific papers published between 2004 and June 2014. It was performed using 16 combinations of keywords in 34 databases, according to PRISMA statement guidelines. Independent reviewers validated the selection criteria. From the 4161 records filtered, 45 met the selection criteria and were selected to be included in this review. This study's outcomes show that the permeable reactive barriers are, indeed, a suitable technology for denitrification and with good performance record but the long-term impact of the use of nanosized zero valent iron in this remediation process, in both on the environment and on the human health, is far to be conveniently known. As a consequence, further work is required on this matter, so that nanosized iron based permeable reactive barriers for the removal of nitrate from drinking water can be genuinely considered an eco-efficient technology.

      PubDate: 2016-09-21T00:30:57Z
       
  • Anthropogenic pressures on productive soils in Corlu and Cerkezkoy
    • Abstract: Publication date: August 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 94
      Author(s): Ezgi Tok
      Unplanned land use is mainly arising from previous regional (local) planning policies based on economic growth, which resulted in the misuse of the land. The fertile lands are converted to industrial/urban areas along with forest areas converted to agricultural zones which directly affect the flora and fauna in a negative way. This study aims to identify the land use transformations by using Remote Sensing and GIS due to prior socio-economic return focused politics resulting in environmental degradations. Additionally, this paper presents an analysis of the transformation of fertile lands into industrial/urban zones with respect to Land Capability Classes. The study area is one of the most urbanized and industrialized zones in Turkey. The reason behind this transformation lies solely in the fact that the aforementioned area is quite appealing to industrialization due to its easy access to infrastructure and its compliance with the spatial requirements. Up until now the development plans of the region have been prepared with a socioeconomic agenda promoting the economic growth while disregarding the ecological and environmental balance, which unfortunately boosted the large-scale degradation of the environment. Although the focus area is within a zone suitable for industrialization, this region also takes place within a wide river basin (Ergene River Basin) making it an ideal location for highly productive crop cultivation (LUC Classes 1 to 4), which is a rare commodity in long term.

      PubDate: 2016-09-21T00:30:57Z
       
  • Micrometeorological measurements and vapour pressure deficit relations
           under in-field rainwater harvesting
    • Abstract: Publication date: August 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 94
      Author(s): Weldemichael A. Tesfuhuney, Sue Walker, Leon D. Van Rensburg, A. Stephan Steyn
      In a cropped field, microclimate and thermal stability conditions depend on the canopy structures and the prevailing weather. The main aim of the study therefore was to characterize the vertical profiles of weather variables within and above a maize (Zea mays L.) canopy and to describe the water vapour pressure deficit (VPD) under different atmospheric and soil surface conditions for both wide and narrow runoff strips with the in-field rainwater harvesting (IRWH) system. Micrometeorological measurements of wind, temperature and relative humidity were performed at eight levels, within canopy (1.8 and 2.1 m), and just above the canopy (2.4, 2.7, 3.0, and 3.3 m) up to reference levels (3.9 and 4.5 m) when the maize reached a maximum height of 2.2 m. Under incomplete canopy cover of the IRWH system, two important factors complicated evapotranspiration estimation, namely the local advection and high temperatures of the bare soil between adjacent plant rows. Diurnal variations of water vapour related to turbulence at each locality and its position in the thermal internal boundary layers. Generally, advection was more pronounced in wide runoff strips than narrow strips. On wide runoff strips the wind was more effective in replacing the air between the rows and maintained a higher driving force for evaporation. The maximum VPD over the narrow strips was observed at reference level during a dry day, at about 2.2 kPa in the afternoon, while wet day VPD reached a maximum of 1.8 kPa. The VPD of the wide runoff strips correlated negatively with wind speed, but showed a fairly positive correlation with some scattered values on wet days after rain. Therefore, profile characteristics within and above plant canopies played a key role in determining the VPD and consequently, could help to explain transpiration rates of crops. Hence, VPD relations enhanced the understanding of the heat energy exchange processes under the heterogeneous nature of maize canopy of the IRWH tillage system.

      PubDate: 2016-09-21T00:30:57Z
       
  • WRF-chem sensitivity to vertical resolution during a saharan dust event
    • Abstract: Publication date: August 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 94
      Author(s): J.C. Teixeira, A.C. Carvalho, Paolo Tuccella, Gabriele Curci, A. Rocha
      The Saharan dust event that occurred between the 22nd and 30th of June 2012 influenced the atmospheric radiative properties over North Africa, the Iberian Peninsula, the Western Mediterranean basin, extending its effects to France and Southern England. This event is well documented in satellite imagery, as well as on the air quality stations over the Iberian Peninsula and the AERONET NASA network. In order to assess the effect of the model vertical resolution on the extinction coefficient fields, as a proxy to the particulate matter concentrations in the atmosphere, the WRF-Chem model was applied during this period over a mother domain with a resolution of 18km, covering Europe and North Africa. To this end five model setups differing in the number of vertical levels were tested. Model skills were evaluated by comparing the model results with CALIPSO and EARLINET LIDAR data. Results show that the model is able to simulate the higher level aerosol transport but it is susceptible to the vertical resolution used. This is due to the thickness of the transport layers which is, eventually, thinner than the vertical resolution of the model. When comparing model results to the observed vertical profiles, it becomes evident that the broad features of the extinction coefficient profile are generally reproduced in all model configurations, but finer details are captured only by the higher resolution simulations.

      PubDate: 2016-09-21T00:30:57Z
       
  • Water quality monitoring in the Paul do Boquilobo Biosphere Reserve
    • Abstract: Publication date: August 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 94
      Author(s): C. Baptista, L. Santos
      The Paul do Boquilobo is an important wetland ecosystem classified by Unesco as a MAB Biosphere reserve also awarded Ramsar site status, representing one of the most important habitats for the resident nesting colony of Cattle Egret (Bulbucus ibis). Yet owing to its location, it suffers from human induced impacts which include industrial and domestic effluent discharges as well as agricultural land use which have negatively impacted water quality. The current study reports the results obtained from the introductory monitoring programme of surface water quality in the Nature Reserve to emphasize the detrimental impact of the anthropogenic activities in the water quality of such an important ecosystem. The study involved physicochemical and biotic variables, microbial parameters and biological indicators. Results after 3 years of monitoring bring to evidence a poor water quality further impaired by seasonal patterns. Statistical analysis of data attributed water quality variation to 3 main parameters – pH, dissolved oxygen and nitrates, indicating heavy contamination loads from both organic and agricultural sources. Seasonality plays a role in water flow and climatic conditions, where sampling sites presented variable water quality data, suggesting a depurative function of the wetland.

      PubDate: 2016-09-21T00:30:57Z
       
  • Review and discussion of homogenisation methods for climate data
    • Abstract: Publication date: August 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 94
      Author(s): S. Ribeiro, J. Caineta, A.C. Costa
      The quality of climate data is of extreme relevance, since these data are used in many different contexts. However, few climate time series are free from non-natural irregularities. These inhomogeneities are related to the process of collecting, digitising, processing, transferring, storing and transmitting climate data series. For instance, they can be caused by changes of measuring instrumentation, observing practices or relocation of weather stations. In order to avoid errors and bias in the results of analysis that use those data, it is particularly important to detect and remove those non-natural irregularities prior to their use. Moreover, due to the increase of storage capacity, the recent gathering of massive amounts of weather data implies also a toilsome effort to guarantee its quality. The process of detection and correction of irregularities is named homogenisation. A comprehensive summary and description of the available homogenisation methods is critical to climatologists and other experts, who are looking for a homogenisation method wholly considered as the best. The effectiveness of homogenisation methods depends on the type, temporal resolution and spatial variability of the climatic variable. Several comparison studies have been published so far. However, due to the absence of time series where irregularities are known, only a few of those comparisons indicate the level of success of the homogenisation methods. This article reviews the characteristics of the most important procedures used in the homogenisation of climatic variables based on a thorough literature research. It also summarises many methods applications in order to illustrate their applicability, which may help climatologists and other experts to identify adequate method(s) for their particular needs. This review study also describes comparison studies, which evaluated the efficiency of homogenisation methods, and provides a summary of conclusions and lessons learned regarding good practices for the use of homogenisation methods.

      PubDate: 2016-09-21T00:30:57Z
       
  • Seasonal drought predictability in Portugal using
           statistical–dynamical techniques
    • Abstract: Publication date: August 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 94
      Author(s): A.F.S. Ribeiro, C.A.L. Pires
      Atmospheric forecasting and predictability are important to promote adaption and mitigation measures in order to minimize drought impacts. This study estimates hybrid (statistical–dynamical) long-range forecasts of the regional drought index SPI (3-months) over homogeneous regions from mainland Portugal, based on forecasts from the UKMO operational forecasting system, with lead-times up to 6months. ERA-Interim reanalysis data is used for the purpose of building a set of SPI predictors integrating recent past information prior to the forecast launching. Then, the advantage of combining predictors with both dynamical and statistical background in the prediction of drought conditions at different lags is evaluated. A two-step hybridization procedure is performed, in which both forecasted and observed 500hPa geopotential height fields are subjected to a PCA in order to use forecasted PCs and persistent PCs as predictors. A second hybridization step consists on a statistical/hybrid downscaling to the regional SPI, based on regression techniques, after the pre-selection of the statistically significant predictors. The SPI forecasts and the added value of combining dynamical and statistical methods are evaluated in cross-validation mode, using the R 2 and binary event scores. Results are obtained for the four seasons and it was found that winter is the most predictable season, and that most of the predictive power is on the large-scale fields from past observations. The hybridization improves the downscaling based on the forecasted PCs, since they provide complementary information (though modest) beyond that of persistent PCs. These findings provide clues about the predictability of the SPI, particularly in Portugal, and may contribute to the predictability of crops yields and to some guidance on users (such as farmers) decision making process.

      PubDate: 2016-09-21T00:30:57Z
       
  • Regionalisation of precipitation for the Iberian Peninsula and climate
           change
    • Abstract: Publication date: August 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 94
      Author(s): A.C. Parracho, P. Melo-Gonçalves, A. Rocha
      Temporal variability of precipitation over the Iberian Peninsula (IP) has high spatial gradients. Therefore, statistics of the temporal behaviour of precipitation and derived quantities over the IP must be estimated taking into account these spatial gradients. Some statistics can be displayed over a map. However there are statistics, such as Probability Density Functions at each location of the IP, that are impossible to display in a map. Because of this, it is mandatory to reduce the number of degrees of freedom which, in this case, consists of a reduction of the time series representative of the IP domain. In this work, we present a spatial partition of the IP region into areas of similar precipitation. For that, an observed dataset of daily-total precipitation for the years between 1951 and 2003 was used. The land-only high resolution data was obtained on a regular grid with 0.2° resolution in the IP domain. This data was subjected to a k-means Cluster Analysis in order to divide the IP into K regions. The clustering was performed using the squared Euclidean distance. Four clusters of IP grid points, defining 4 IP regions, were identified. The grid points in each region share the same time-varying behaviour which is different from region to region. The annual precipitation discriminates the following regions: (1) north Iberia, (2) a large region extending from the centre to the Mediterranean shores of the IP, (3) a large region ranging from the centre to the western and southwestern shores of the Iberia, and (4) northwest Iberia. The regions obtained for the four seasons of the year are similar. These results are consistent with the thermodynamic characteristics described in the available literature. These Iberian regions were used to assess climate change of seasonal precipitation from the multi-model ensemble of the fifteen simulations provided by the European project ENSEMBLES. Probability Density Functions of annual- and seasonal-total precipitation, consecutive dry days, and total precipitation above the 95th percentile, averaged in each region were estimated for a reference climate (1961–1960), a near-future climate (2021–2050), and a distant-future climate (2069–2098). Climate change projections are based on comparisons of these functions between each future climate and the reference climate. Finally, we emphasize that: (i) the methodology used here, based on Cluster Analysis, can be used to regionalise other areas of the world, and (ii) the identified regions of the IP can be used to represent the Iberian precipitation by four time series that can be subjected to further analysis, whose results can be presented in a concise manner.

      PubDate: 2016-09-21T00:30:57Z
       
  • SPI drought class prediction using log-linear models applied to wet and
           dry seasons
    • Abstract: Publication date: August 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 94
      Author(s): Elsa E. Moreira
      A log-linear modelling for 3-dimensional contingency tables was used with categorical time series of SPI drought class transitions for prediction of monthly drought severity. Standardized Precipitation Index (SPI) time series in 12- and 6-month time scales were computed for 10 precipitation time series relative to GPCC datasets with 2.5° spatial resolution located over Portugal and with 112 years length (1902–2014). The aim was modelling two-month step class transitions for the wet and dry seasons of the year and then obtain probability ratios – Odds – as well as their respective confidence intervals to estimate how probable a transition is compared to another. The prediction results produced by the modelling applied to wet and dry season separately, for the 6- and the 12-month SPI time scale, were compared with the results produced by the same modelling without the split, using skill scores computed for the entire time series length. Results point to good prediction performances ranging from 70 to 80% in the percentage of corrects (PC) and 50–70% in the Heidke skill score (HSS), with the highest scores obtained when the modelling is applied to the SPI12. The adding up of the wet and dry seasons introduced in the modelling brought improvements in the predictions, of about 0.9–4% in the PC and 1.3–6.8% in the HSS, being the highest improvements obtained in the SPI6 application.

      PubDate: 2016-09-21T00:30:57Z
       
  • The effect of roughness in simultaneously retrieval of land surface
           parameters
    • Abstract: Publication date: August 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 94
      Author(s): Mina Moradizadeh, Mohammad R. Saradjian
      Using remotely-sensed data, various soil moisture estimation models have been developed for bare soil areas. Previous studies have shown that the brightness temperature (BT) measured by passive microwave sensors were affected by characteristics of the land surface parameters including soil moisture, vegetation cover and soil roughness. Therefore knowledge of vegetation cover and soil roughness is important for obtaining frequent and global estimations of land surface parameters especially soil moisture. In this study, a model called Simultaneous Land Parameters Retrieval Model (SLPRM) that is an iterative least-squares minimization method is proposed. The algorithm estimates surface soil moisture, land surface temperature and canopy temperature simultaneously in vegetated areas using AMSR-E (Advance Microwave Scanning Radiometer-EOS) brightness temperature data. The simultaneous estimations of the three parameters are based on a multi-parameter inversion algorithm which includes model construction, calibration and validation using observations carried out for the SMEX03 (Soil Moisture Experiment, 2003) region in the South and North of Oklahoma. Roughness parameter has also been included in the algorithm to increase the soil parameters retrieval accuracy. Unlike other methods, the SLPRM method works efficiently in all land covers types. The study focuses on soil parameters estimation by comparing three different scenarios with the inclusion of roughness data and selects the most appropriate one. The difference between the resulted accuracies of scenarios is due to the roughness calculation approach. The analysis on the retrieval model shows a meaningful and acceptable accuracy on soil moisture estimation according to the three scenarios. The SLPRM method has shown better performance when the SAR (Synthetic Aperture RADAR) data are used for roughness calculation.

      PubDate: 2016-09-21T00:30:57Z
       
  • Influence of deposition of fine plant debris in river floodplain shrubs on
           flood flow conditions – The Warta River case study
    • Abstract: Publication date: August 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 94
      Author(s): Robert Mazur, Tomasz Kałuża, Joanna Chmist, Natalia Walczak, Ireneusz Laks, Paweł Strzeliński
      This paper presents problems caused by organic material transported by flowing water. This material is usually referred to as plant debris or organic debris. Its composition depends on the characteristic of the watercourse. For lowland rivers, the share of the so-called small organic matter in plant debris is considerable. This includes both various parts of water plants and floodplain vegetation (leaves, stems, blades of grass, twigs, etc.). During floods, larger woody debris poses a significant risk to bridges or other water engineering structures. It may cause river jams and may lead to damming of the flowing water. This, in turn, affects flood safety and increases flood risk in river valleys, both directly and indirectly. The importance of fine plant debris for the phenomenon being studied comes down to the hydrodynamic aspect (plant elements carried by water end up on trees and shrubs, increase hydraulic flow resistance and contribute to the nature of flow through vegetated areas changed from micro-to macro-structural). The key part of the research problem under analysis was to determine qualitative and quantitative debris parameters and to establish the relationship between the type of debris and the type of land use of river valleys (crop fields, meadows and forested river sections). Another problem was to identify parameters of plant debris for various flow conditions (e.g. for low, medium and flood flows). The research also included an analysis of the materials deposited on the structure of shrubs under flood flow conditions during the 2010 flood on the Warta River.

      PubDate: 2016-09-21T00:30:57Z
       
  • High resolution WRF climatic simulations for the Iberian Peninsula: Model
           validation
    • Abstract: Publication date: August 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 94
      Author(s): Martinho Marta-Almeida, João C. Teixeira, Maria J. Carvalho, Paulo Melo-Gonçalves, Alfredo M. Rocha
      A high resolution atmospheric modelling study was done for a 20-year recent historical period. The dynamic downscaling approach adopted used the Max Planck Institute Earth System Model (MPI-ESM) to drive the WRF running in climate mode. Three online nested domains were used covering part of the North Atlantic and Europe, with a resolution 81 km, and reaching 9 km in the innermost domain which covers the Iberian Peninsula. This paper presents the validation of the WRF configuration, which is based on historic simulations between 1986 and 2005 and observational datasets of near surface temperature and precipitation for the same period. The validation was done in terms of comparison of probability distributions between model results and observations, as daily climatologies, spatially averaged inside subdomains obtained with cluster analysis of the observations, for each of the four seasons. In addition, Taylor diagrams are presented for each of the seasons and subdomains. This validation approach was repeated with the results of a new WRF simulation with the same parameterisations but forced by the ERA-Interim reanalysis. The capacity of the MPI-ESM driven WRF configuration to compare with observations and in a manner similar to the ERA-Interim driven WRF, ensures the capacity of the configuration for climate and climate change studies. Considering the difficulty to simulate extremes in long term simulations, the results showed a comfortable comparison of both models (forced by climate model and reanalysis results) with observations. This provides us confidence on the continuity of using the MPI-ESM driven WRF configuration for climate studies.

      PubDate: 2016-09-21T00:30:57Z
       
  • A dependence modelling study of extreme rainfall in Madeira Island
    • Abstract: Publication date: August 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 94
      Author(s): Délia Gouveia-Reis, Luiz Guerreiro Lopes, Sandra Mendonça
      The dependence between variables plays a central role in multivariate extremes. In this paper, spatial dependence of Madeira Island's rainfall data is addressed within an extreme value copula approach through an analysis of maximum annual data. The impact of altitude, slope orientation, distance between rain gauge stations and distance from the stations to the sea are investigated for two different periods of time. The results obtained highlight the influence of the island's complex topography on the spatial distribution of extreme rainfall in Madeira Island.

      PubDate: 2016-09-21T00:30:57Z
       
  • An exploratory study of spatial annual maximum of monthly precipitation in
           the northern region of Portugal
    • Abstract: Publication date: August 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 94
      Author(s): D. Prata Gomes, M.M. Neves, E. Moreira
      Adequately analyzing and modeling the extreme rainfall events is of great importance because of the effects that their magnitude and frequency can have on human life, agricultural productivity and economic aspects, among others. A single extreme event may affect several locations, and their spatial dependence has to be appropriately taken into account. Classical geostatistics is a well-developed field for dealing with location referenced data, but it is largely based on Gaussian processes and distributions, that are not appropriate for extremes. In this paper, an exploratory study of the annual maximum of monthly precipitation recorded in the northern area of Portugal from 1941 to 2006 at 32 locations is performed. The aim of this paper is to apply max-stable processes, a natural extension of multivariate extremes to the spatial set-up, to briefly describe the models considered and to estimate the required parameters to simulate prediction maps.

      PubDate: 2016-09-21T00:30:57Z
       
  • Recent trends of extreme temperature indices for the Iberian Peninsula
    • Abstract: Publication date: August 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 94
      Author(s): D. Fonseca, M.J. Carvalho, M. Marta-Almeida, P. Melo-Gonçalves, A. Rocha
      Climate change and extreme climate events have a significant impact on societies and ecosystems. As a result, climate change projections, especially related with extreme temperature events, have gained increasing importance due to their impacts on the well-being of the population and ecosystems. However, most studies in the field are based on coarse global climate models (GCMs). In this study, we perform a high resolution downscaling simulation to evaluate recent trends of extreme temperature indices. The model used was Weather Research and Forecast (WRF) forced by MPI-ESM-LR, which has been shown to be one of the more robust models to simulate European climate. The domain used in the simulations includes the Iberian Peninsula and the simulation covers the 1986–2005 period (i.e. recent past). In order to study extreme temperature events, trends were computed using the Theil-Sen method for a set of temperature indexes defined by the Expert Team on Climate Change Detection and Indices (ETCCDI). For this, daily values of minimum and maximum temperatures were used. The trends of the indexes were computed for annual and seasonal values and the Mann-Kendall Trend test was used to evaluate their statistical significance. In order to validate the results, a second simulation, in which WRF was forced by ERA-Interim, was performed. The results suggest an increase in the number of warm days and warm nights, especially during summer and negative trends for cold nights and cold days for the summer and spring. For the winter, contrary to the expected, the results suggest an increase in cold days and cold nights (warming hiatus). This behavior is supported by the WRF simulation forced by ERA-Interim for the autumn days, pointing to an extension of the warming hiatus phenomenon to the remaining seasons. These results should be used with caution since the period used to calculate the trends may not be long enough for this purpose. However, the general sign of trends are similar for both simulations despite some differences in their magnitudes.

      PubDate: 2016-09-21T00:30:57Z
       
  • On the relationship between atmospheric water vapour transport and
           extra-tropical cyclones development
    • Abstract: Publication date: August 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 94
      Author(s): Juan A. Ferreira, Margarida L.R. Liberato, Alexandre M. Ramos
      In this study we seek to investigate the role of atmospheric water vapour on the intensification of extra-tropical cyclones over the North Atlantic Ocean and more specifically to investigate the linkage between atmospheric rivers' conditions leading to the explosive development of extra-tropical cyclones. Several WRF-ARW simulations for three recent extra-tropical storms that had major negative socio-economic impacts in the Iberian Peninsula and south-western Europe (Klaus, 2009; Gong, 2013 and Stephanie, 2014) are performed in which the water vapour content of the initial and boundary conditions are tuned. Analyses of the vertically integrated vapour transport show the dependence of the storms' development on atmospheric water vapour. In addition, results also show changes in the shape of the jet stream resulting in a reduction of the upper wind divergence, which in turn affects the intensification of the extra-tropical cyclones studied. This study suggests that atmospheric rivers tend to favour the conditions for explosive extra-tropical storms' development in the three case studies, as simulations performed without the existence of atmospheric rivers produce shallow mid-latitude cyclones, that is, cyclones that are not so intense as those on the reference simulations.

      PubDate: 2016-09-21T00:30:57Z
       
  • Identification of nitrate sources in groundwater and potential impact on
           drinking water reservoir (Goczałkowice reservoir, Poland)
    • Abstract: Publication date: August 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 94
      Author(s): Joanna Czekaj, Sabina Jakóbczyk-Karpierz, Hanna Rubin, Sławomir Sitek, Andrzej J. Witkowski
      Goczałkowice dammed reservoir (area – 26 km2) is a strategic object for flood control in the Upper Vistula River catchment and one of the most important source of drinking water in the Upper Silesian Industrial Region (Southern Poland). Main aims of the investigation were identification of sources of nitrate and assessment of their significance in potential risk to groundwater quality. In the catchment area monitoring network of 22 piezometers, included 14 nested, have been installed. The significant spatial and seasonal differences in chemical composition between northern and southern part of the catchment were indicated based on the groundwater sampling conducted twice – in autumn 2011 and spring 2012. Maximum observed concentrations of nitrate were identified in northern part of the study area 255 mg/L as a results of inappropriate sewage management and agriculture activity. Results, based on the combines multi-scale hydrogeological and hydrochemical field studies, groundwater flow and transport modelling, dual stable isotope approach and geochemical modelling indicate mainly agriculture and inappropriate sewage water management as a sources of NO 3 − contamination of groundwater which moreover is affected by geochemical processes. In general, contaminated groundwater does not impact surface water quality. However, due to high concentration of nitrate in northern part a continues measurements of nitrogen compounds should be continued and used for reducing uncertainty of the predictive scenarios of the mass transport modelling in the study area.

      PubDate: 2016-09-21T00:30:57Z
       
  • A comparative analysis of site-specific response spectral amplification
           models
    • Abstract: Publication date: Available online 16 September 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Valerio Poggi, Benjamin Edwards, Donat Fäh
      In the framework of the Seismic Hazard Harmonization in Europe (SHARE) project, the Swiss Seismological Service (SED) has performed an evaluation of two procedures developed to produce soil amplification models for 5% damped pseudo-spectral acceleration response spectra, each using different parameters to describe the soil properties. The goal of the work presented here is to evaluate the statistical consistency of the methods, with particular regard to their applicability to engineering practice. Additionally, we compare the results with those from a methodology internally developed by the SED, which is based on spectral modeling of ground motion using the quarter-wavelength approximation to parameterize soil conditions. Soil amplification is computed with respect to reference rock condition as defined for the probabilistic seismic hazard assessment performed during the SHARE project. For the comparison, a residual analysis was performed between the computed soil-amplification functions from the three different methodologies, over a number of selected sites spanning different soil classes and ground motion levels. The analysis of the average residuals of these functions is useful to highlight the main differences between the proposed approaches, with special regard to the impact of soil resonances and anelastic attenuation within different frequency bands. The assessment was performed on a group of 88 selected stations of the Japanese KiKNet strong-motion network, for which complete logs of the shear-wave velocity profiles are available, in addition to a significant number of earthquake recordings. In a first step, average residuals were computed. Subsequently, amplification variability related to soil classes was investigated. The target of this second step was to perform the comparison by separately analyzing the impact of different soil and velocity classes, according to a soil-classification scheme proposed by Aristotle University of Thessaloniki (AUTH). In this paper the main results of these investigations are summarized and, when applicable, an interpretation of our findings is given.

      PubDate: 2016-09-21T00:30:57Z
       
  • Modelling analysis of water-use efficiency of Maize in Heihe river basin
    • Abstract: Publication date: Available online 6 September 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Guofeng Wang, Jiancheng Chen, Qing Zhou, Xi Chu, Xiaoxue Zhou


      PubDate: 2016-09-08T13:56:03Z
       
  • Water Ecological Function Zoning in Heihe River Basin, Northwest China
    • Abstract: Publication date: Available online 7 September 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Dongdong Chen, Gui Jin, Qian Zhang, Aisha Olushola Arowolo, Yifan Li
      Rapid urbanization coupled with increase in population growth rate in recent years has accelerated economic pressure on the ecological environment leading to a gradual deterioration of global and regional environment. This has particularly resulted into water contamination and shortage of water resources thus posing a great threat to human survival. How to guaranteeing sustainable use of basin water resources has attracted more and more attentions. The Heihe River Basin is the secondary longest river inland China and the significantly water source of Hexi Corridor, the problem of water pollution, ecological environment deterioration and the shortage of water has seriously threatened the ecological system of the Heihe River Basin. In this study, through depicting the characteristics of natural environment, human activities, water ecosystem services and other factors in Heihe River Basin we delineated the water ecological function in Heihe River using the principal components analysis and the K-means clustering method. In the study, Heihe river Basin is divided into 3 primary level areas and 8 secondary level sub-areas. Water ecological characteristics analysis showed that the spatial distribution of the water ecological function of Heihe River Basin was not uniform, which are mainly showed in three aspects, function of windproof and sand fixation, function of soil erosion prevention and function of water sources conservation. The results of this study can provide effective and scientific theoretical references for the integrated water sources management and the ecological function optimization of the Heihe River Basin.

      PubDate: 2016-09-08T13:56:03Z
       
  • Effects of salinity on dynamics of soil carbon in degraded coastal
           wetlands: implications on wetland restoration
    • Abstract: Publication date: Available online 30 August 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Qingqing Zhao, Junhong Bai, Qiongqiong Lu, Guangliang Zhang
      To investigate the effects of salinity on dynamics of soil carbon contents and stocks, soil samples were collected at a depth of 30 cm at four sampling sites (Sites B, T, S and P) along a salinity gradient in a drained coastal wetland, the Yellow River Delta, China. The salinity of these four sites ranked in the order: B (8.68 ± 4.25 ms/cm) > T (5.89 ± 3.17 ms/cm) > S (3.19 ± 1.01 ms/cm) > P (2.26 ± 0.39 ms/cm). Soil total carbon (TC), soil organic carbon (SOC), and soil microbial biomass carbon (MBC) were measured. Based on these data, soil organic carbon density (SOCD) and soil microbial biomass carbon density (MBCD) were calculated at four sites. The results showed that the mean concentrations of TC and MBC showed a general deceasing tendency with increasing salinities in the top 30 cm of soils. The values of SOCD and MBCD exhibited similar tendency along the salinity gradient. As for profile distribution pattern, The C/N ratios ranged from 8.28 to 56.51. The microbial quotient values at four sampling sites were quite low, ranging from 0.06-0.19. Higher C/N ratios were found in samples with high salinity. Correlation analysis showed that the concentrations of TC and MBC at four sampling sites were significantly negatively correlated with salinity (P < 0.01 or P < 0.05), indicating that salinity could inhibit soil carbon accumulation and microbial activities.

      PubDate: 2016-09-03T13:21:07Z
       
  • A Method to Correct Eddy Covariance Flux Underestimates under an Advective
           Environment for Arid or Semi-arid Regions
    • Abstract: Publication date: Available online 31 August 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Hongbo Su, Yongmin Yang, Lina Xu, José L. Chávez, Steven R. Evett, Terry A. Howell, Jing Tian, Shaohui Chen, Jinyan Zhan
      Water scarcity is one of the main factors limiting agricultural development in arid or semi-arid areas. Accurate Evapotranspiration (ET) observations and estimations are crucial in water cycle studies to estimate water losses from the terrestrial surfaces to the atmosphere to close the regional water budget. The eddy covariance (EC) method is an important technique measure ET and other land surface energy fluxes. However, the underestimation of energy fluxes and the problem of EC energy balance non-closure are far from solved. In this study, a new method is proposed to account for advection in order to correct EC data under advective environments. This advection based method was applied to data from Bushland, TX, which is subject to dry air and strong winds. Observations from two identical EC systems as well as two precision monolithic weighing lysimeters were used in this analysis. Both EC sites showed significant underestimates of evapotranspiration (ET) compared with lysimeter measurements. The daily energy balance closure for NE01 and SE02 sites were 0.78 and 0.74 respectively. The advection correction method provided improved performance in daytime, and it is more suitable for ET estimate than forcing closure under the advective environment. For nighttime, two methods (NCM1 and NCM2) were proposed to correct EC underestimates. Finally, all the corrected ET values were compared with the lysimeter measurements. For NE01 site, the MAD (mean absolute deviation) and the RMSD (root mean square deviation) were 47.72 W/m2 and 67.66 W/m2, respectively; and the r2 (coefficient of determination) was 0.85. For SE02 site, the MAD and RMSD were 30.59 W/m2 and 44.43 W/m2; and the r2 was 0.93. The statistical measures illustrated that the proposed methods are functional and appropriate under an advective environment. The accurate estimate of actual evapotranspiration will benefit both the strategic planning of optimal water uses and the improved understanding the environmental and hydrological processes.

      PubDate: 2016-09-03T13:21:07Z
       
  • The 24 May 2014 (Mw6.8) earthquake (North Aegean Trough): spatiotemporal
           evolution, source and slip model from teleseismic data
    • Abstract: Publication date: Available online 28 August 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Anastasia Kiratzi, Eva Tsakiroudi, Christoforos Benetatos, George Karakaisis
      We use teleseismic data to calculate the source model of the 24 May 2014 earthquake and regional catalogues to examine the spatial-temporal characteristics of the sequence. The sequence started in Saros Basin but almost simultaneously aftershocks spread along a ∼200 km zone, activating the entire North Aegean Trough. The aftershock sequence was rich in moderate (M<4) size events, but very deficient in strong events – only two Mw4.9 aftershocks-a characteristic observed in previous sequences in the region. The teleseismic waveforms were best fit by two sub-events, which were lagged by 18s in time and by a 50 km jump in space, along the same fault line. The centroid depth of the first sub-event is 22km, at the base of the lower crust, and for the second is 14 km. The resolved total source time function is ∼30s. The finite-fault slip model is characterized by an asymmetric bilateral rupture propagation, to the west and east of the hypocentre. The major slip is confined downdip from the hypocentre, within the deeper 12-25km part. This deep slip migrated updip from the hypocentre to form the second slip patch, in the eastward segment. In all our models the maximum dislocation was of the order of 1m. For our preferred model parametrization, the rupture speed is 3km/s, and the scalar moment equal to 1.76×1019 Nm (Mw6.8). This earthquake highlighted the fact that strike-slip faulting in the North Aegean Sea, can attain large lengths and activate very wide zones, reaching densely populated regions.

      PubDate: 2016-08-29T12:34:54Z
       
  • Electrospun and functionalized PVDF/PAN composite for the removal of trace
           metals in contaminated water
    • Abstract: Publication date: Available online 29 August 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): R.M. Nthumbi, A.A. Adelodun, J.C. Ngila
      The electrospinning of a nanofiber composite of polyvinylidene fluoride (PVDF) and polyacrylonitrile (PAN) in a dimethylformamide (DMF) solvent was carried out prior to functionalization by free radical grafting of acrylic acid (AA) brushes. Subsequent application for the removal of Pb2+ and Cd2+ from contaminated water is reported. Free radicals were initiated on the polymeric nanofiber composite using 5% 2,2′-Azobis(2-methylpropionitrile) (AIBN) in acetone. Upon solvent removal by air-drying, AA was added and grafting (in a methanol-water solvent system) was carried out in an oil bath at 70 °C for 5 h under nitrogen atmosphere. Structural and chemical characterization of the composite was done using scanning electron microscope (SEM), nitrogen sorption at 77 K (BET method), goniometer and Fourier transform infrared spectrometer (FTIR), while changes in metal ion concentration during batch adsorption were monitored using inductively coupled plasma optical emission spectrometer (ICP-OES). Through isotherm study, the adsorption was confirmed to follow both Langmuir and Freundlich models whilst adsorption kinetic studies showed that the adsorption rate is of pseudo-second order. In furtherance, the respective values for adsorption capacity and estimated removal efficiency for Pb2+ and Cd2+ were 1.585 and 0.164 mg.g-1, 90% and 80% respectively, while a 5% loss in regeneration efficiency after 10 cycles was also observed. Consequently, the nanocomposite was found efficient when applied to the removal of Pb2+ and Cd2+ from contaminated water.

      PubDate: 2016-08-29T12:34:54Z
       
  • When good practices by water committees are not relevant: sustainability
           of small water infrastructures in semi-arid mozambique
    • Abstract: Publication date: Available online 24 August 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Raphaelle Ducrot
      This paper explores the contradiction between the need for large scale interventions in rural water supplies and the need for flexibility when providing support for community institutions, by investigating the implementation of the Mozambique - National Rural Water Supply and Sanitation Program in a semi-arid district of the Limpopo Basin. Our results showed that coordinated leadership by key committee members, and the level of village governance was more important for borehole sustainability than the normative functioning of the committee. In a context in which the centrality of leadership prevails over collective action the sustainability of rural water infrastructure derives from the ability of leaders to motivate the community to provide supplementary funding. This, in turn, depends on the added value to the community of the water points and on village politics. Any interventions that increased community conflicts, for example because of lack of transparency or unequitable access to the benefit of the intervention, weakened the coordination and the collective action capacity of the community and hence the sustainability of the infrastructures even if the intervention was not directly related to water access. These results stress the importance of the project/program implementation pathway.

      PubDate: 2016-08-25T12:16:25Z
       
  • Surface geology and morphologic effects on seismic site response: the
           study case of Lampedusa, Italy
    • Abstract: Publication date: Available online 22 August 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): F. Panzera, G. Lombardo, S. Sicali, S. D’Amico
      A joint Italo-Maltese research project (Costituzione di un Sistema Integrato di Protezione Civile Transfrontaliero Italo-Maltese, SIMIT) was financially supported by the European community with the aim to produce hazard maps in the area between the south-eastern Sicilian coast and the Sicily Channel including the islands of Lampedusa and Malta. In the frame of this project, the present study investigates the characteristics of the local seismic response in Lampedusa, a carbonate shelf belonging to the foreland domain at the northern edge of the African plate. Ninety-two ambient noise recordings were collected and processed through spectral ratio techniques. Polarization of the horizontal component of motion was also investigated in order to set into evidence possible directional effects. Results point out that in the central part of the island, where the most ancient and rigid terrains outcrop most of the spectral ratio plots show no particular site effects. On the other hand, nearby morphologic escarpments and fault lines, pronounced spectral ratio peaks in the frequency range 2.0 – 5.0 Hz are observed. These peaks, as highlighted by polarization analysis, are clearly directional with the largest amplification occurring with high angle (60°-90°) to the structures strike. Moreover, in sites located close to recent and soft deposits outcrops other significant seismic site effects at frequency higher than 5.0 Hz are identified. We can however assert that, rather than the surface lithology, the presence of cliff areas and tectonic structures strongly influence the local amplification of the ground motion and the occurrence of directional effects.

      PubDate: 2016-08-25T12:16:25Z
       
  • Polyethyleneimine-carbon nanotube polymeric nanocomposite adsorbents for
           the removal of Cr6+ from water
    • Abstract: Publication date: Available online 17 August 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Shepherd S. Sambaza, Monaheng L. Masheane, Soraya P. Malinga, Edward N. Nxumalo, Sabelo D. Mhlanga
      This work reports on the synthesis of multi-walled carbon nanotubes (MWCNTs) and their use in branched polyethyleneimine-multiwalled carbon nanotube (PEI-MWCNT) polymeric nanocomposite adsorbents for the removal of Cr6+ from contaminated water. The nanostructured materials were characterized using TEM, Raman, FTIR, BET surface area and zeta potental measurements. TEM confirmed the average diameter of the MWCNTs to be 25 nm. The point of zero-charge of PEI was at pH 8 and that of PEI-MWCNTs was at pH 7.7. FTIR analysis confirmed the formation of a new bond (–C=O at 1716 cm-1) between the functional groups on the MWCNTs and PEI. Batch adsorption and kinetic studies showed that the PEI-MWCNT nanocomposite materials were more efficient in the removal of Cr6+ solution from water samples. The optimum conditions for adsorption were pH ≤ 4, contact time of 60 min. When the PEI-MWCNT dosage was increased the adsorption capacity increased. The kinetic adsorption data obtained for Cr6+ solution followed pseudo-second order model. The adsorption of Cr6+ solution reached equilibrium within 60 min of contact time with a removal of 99%. The adsorbents were effective even after 5 cycles of use.

      PubDate: 2016-08-19T11:42:33Z
       
  • Reception conditions of low frequency (LF) transmitter signals onboard
           DEMETER micro-satellite
    • Abstract: Publication date: Available online 12 August 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): M.Y. Boudjada, P.F. Biagi, E. Al-Haddad, P.H.M. Galopeau, B. Besser, D. Wolbang, G. Prattes, H. Eichelberger, G. Stangl, M. Parrot, K. Schwingenschuh
      We analyse the flux density variation associated to low frequency (LF) broadcasting transmitters observed by the ICE electric field experiment onboard DEMETER micro-satellite, observed from 01st Jan. to 09th Dec. 2010. We select five stations localised around the Mediterranean and the Black seas: Tipaza (252 kHz, 02°28’E, 36°33’N, Algeria), Roumoules (216 kHz, 06°08’E, 43°47’N, Monte Carlo), Polatli (180 kHz, 32°25’E, 39°45’N, Turkey), Nadour (171 kHz, 02°55’W, 35°02’N, Morocco) and Brasov (153 kHz, 25°36’E,45°40’, Romania). The detection of the LF transmitter signals by DEMETER micro-satellite is found to depend on the radiated power, the emitted frequency, and the orbit paths with regard to the location of the stations. This leads us to characterise the reception condition of the LF signals and to define time intervals where the detection probability is high. We show that LF signal are regularly recorded, each 12 days, when the satellite is above the broadcasting station. The signal intensity levels are principally significant during the solar activity. Hence we find that the solar and the geomagnetic activities are slightly correlated to the maxima of LF signal as recorded by DEMETER. Also we note a drop of the intensity level several days before the occurrence of earthquakes in/around the Mediterranean and Black seas.

      PubDate: 2016-08-15T11:36:45Z
       
  • Forecast and optimal allocation of production, living and ecology water
           consumption in Zhangye, China
    • Abstract: Publication date: Available online 6 August 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Qian Xu, Wei Song, Ying Zhang
      The water crisis is one of three crises that are persecuting the world. China is among the countries that face severe water shortages. Water scarcity and water pollution have seriously affected China's sustainable development in terms of the economy and society. Water resources per capita of China is only one quarter of the world's average. In addition, about 70 percent of China’s rivers, lakes, and reservoirs are affected by pollution. Due to limited water resources, a crucial issue for the sustainable development of the watershed is how to resolve the human/nature competition for water and how to achieve the coordinated development of the economy, society and ecology. On the basis of defining water consumption for production, living and ecology (WPLE), this paper proposes a framework for forecasting and optimally allocating WPLE. Using Zhangye, in the middle reaches of the Heihe River Basin as the case study area, we forecasted and optimally allocated WPLE under three development scenarios, i.e. the conventional development scenario (CDS), the economy-priority development scenario (EPDS) and the environmentally sustainable development scenario (ESDS). In 2010, the proportions of WPLE in Zhangye were 87.73%, 2.74% and 9.53%, respectively. In 2020, the proportions of WPLE will be 74.80%, 4.50% and 20.70% under the CDS, 76.16%, 5.27% and 18.57% under the EPDS, and 74.99%, 4.51% and 20.50% under the ESDS. In the future, the proportion of production water consumption of Zhangye will drastically decrease, while the proportion of ecological water consumption will significantly increase. The main contradiction of the co-evolution of WPLE of Zhangye is the competitiveness of production and living water consumption with ecological water consumption.

      PubDate: 2016-08-10T11:13:00Z
       
  • Site amplification at the city scale in Basel (Switzerland) from
           geophysical site characterization and spectral modelling of recorded
           earthquakes
    • Abstract: Publication date: Available online 6 August 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Clotaire Michel, Donat Fäh, Benjamin Edwards, Carlo Cauzzi
      Hazard assessment at the city scale requires a detailed characterization of the effect of surface geology on ground motion (site effects). Though this analysis is commonly achieved using geophysical site characterization and site response modelling, we propose here a complementary analysis based on amplification functions retrieved from Empirical Spectral Modelling (ESM) of earthquake recordings. We applied this method to the city of Basel (Switzerland) that benefits from a detailed microzonation and a dense Strong Motion Network with 21 modern free-field stations. We first verified the accuracy of ESM amplification functions for this region and used them to determine the bedrock interface at a site with a detailed velocity profile. While the interface between Upper and Lower Tertiary was, until now, considered responsible for the fundamental frequency of resonance in the Rhine Graben, we found that the bedrock interface in fact lies at the Mesozoic limestone. We also investigated the second peak of the H/V ratios that is clustered in a particular area of the basin where amplification is found to be different. We successfully used the ESM amplification functions to verify the microzonation of 2006 and would strongly advise the installation of strong motion stations where such studies are performed in the future. Outside the Rhine Graben, where shallow sediments are found, we propose an amplification functional form based on ESM and the fundamental frequency of resonance. Finally, we combined all our findings and generated amplification maps of the response spectrum at any period of interest for earthquake engineering. This map is proposed for a high resolution real-time implementation in ShakeMap and will be used for seismic loss assessment.
      Graphical abstract image

      PubDate: 2016-08-10T11:13:00Z
       
  • Is small-scale irrigation an efficient pro-poor strategy in the upper
           Limpopo Basin in Mozambique?
    • Abstract: Publication date: Available online 27 June 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Raphaelle Ducrot
      In Sub-Saharan Africa, there is evidence that households with access to small-scale irrigation are significantly less poor than households that do not have access to irrigation. However, private motopumps tend to be distributed inequitably. This paper investigates the success of explicit pro-poor interventions with emphasis on small-scale irrigation in the semi-arid Limpopo Basin in Mozambique. It reveals that high irrigation costs are progressively excluding the poor, who are unable to generate a cash income from other activities they need to fund irrigation. In addition, the operation of collective schemes involving the poor is being jeopardized by the development of private irrigation schemes, which benefit from hidden subsidies appropriated by local elites. This results in unequal access to irrigation, which can cause resentment at community level. This weakens community cohesiveness, as well as communities' capacities for collective action and coordination, which are crucial for collective irrigation.

      PubDate: 2016-08-10T11:13:00Z
       
  • Recent trends of extreme precipitation indices in the Iberian Peninsula
           using observations and WRF model results
    • Abstract: Publication date: Available online 27 June 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): S. Bartolomeu, M.J. Carvalho, M. Marta-Almeida, P. Melo-Gonçalves, A. Rocha
      Spatial and temporal distributions of the trends of extreme precipitation indices were analysed between 1986 and 2005, over the Iberian Peninsula (IP). The knowledge of the patterns of extreme precipitation is important for impacts assessment, development of adaptation and mitigation strategies. As such, there is a growing need for a more detailed knowledge of precipitation climate change. This analysis was performed for Portuguese and Spanish observational datasets and results performed by the Weather Research and Forecast (WRF) model forced by the ERA-Interim reanalysis. Extreme precipitation indices recommended by the Expert Team for Climate Change Detection Monitoring and Indices were computed, by year and season. Then, annual and seasonal trends of the indices were estimated by Theil-Sen method and their significance was tested by the Mann-Kendal test. Additionally, a second simulation forced by the Max Planck Institute Earth System Model (MPI-ESM), was considered. This second modelling configuration was created in order to assess its performance when simulating extremes of precipitation. The annual trends estimated for the 1986–2005, from the observational datasets and from the ERA-driven simulation reveal: 1) negative statistically significant trends of the CWD index in the Galicia and in the centre of the IP; 2) positive statistically significant trends of the CDD index over the south of the IP and negative statistically significant trends in Galicia, north and centre of Portugal; 3) positive statistically significant trends of the R75p index in some regions of the north of the IP; 4) positive statistically significant trends in the R95pTOT index in the Central Mountains Chain, Leon Mountains and in the north of Portugal. Seasonally, negative statistically significant trends of the CWD index were found in Galicia, in winter and in the south of the IP, in summer. Positive statistically significant trends of the CWD index were identified in the Leon Mountains, in spring, and in Galicia, in autumn. For the CDD index, negative statistically significant trends were seen in Valencia, in the spring, and, in Galicia and Portugal (north and centre), in summer. Positive statistically significant trends of the CDD index were found: in the east of the IP, in the winter; in the Cantabrian Mountain, in the spring; and, in the south of the IP, in summer. Regarding to the R75p index, negative statistically significant trends were found in Galicia, in winter and positive statistically significant trends in the north of Portugal, in spring and in the Central Mountains Chain and north of Portugal, in autumn. For the R95pTOT index, negative statistically significant trends were found over the Sierra Cuenca and Sierra Cazorla, in winter and positive statistically significant trends were found over the Sierra Cebollera, in winter and in Castile-la Mancha region, in spring. The results of the annual and seasonal trends of the extreme precipitation indices performed for observational datasets and the simulation forced by ERA-Interim, are similar. The results obtained for the simulation forced by MPI-ESM are not satisfactory, and can be a source of criticism for the use of simulation forced by MPI-ESM in this type of climate change studies. Even for the relatively short period used, the WRF model, when properly forced is a useful tool due to the similar results of Portuguese and Spanish observational datasets and the simulation forced by ERA-Interim.

      PubDate: 2016-08-10T11:13:00Z
       
  • Strategy for Management of Lake-Catchment System Integrated with Natural
           and Anthropogenic Factors in China
    • Abstract: Publication date: Available online 27 June 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Zhandong Yang, Feng Wu, Xing Gao
      Lake eutrophication that has caused severe damages to aquatic ecosystems is a hot issue in the field of water pollution control, so analyzing its process and driving mechanism is of great significance. In this study, we detected its major driving factors based on an observed dataset and assessed the impacts of these factors. Firstly, empirical econometric models were used to ascertain the Per capita GDP and the percentage of impervious surface, which are significantly related with the eutrophication level. Eutrophication is slightly affected by anthropogenic disturbance, but is negatively related to the supply coefficient. Secondly, all driving factors are divided into two categories, including the stresses caused by human activities and the comprehensive health status, which are expressed as the two coordinate axes of an indicator-matrix. Thirdly, lake classification, which is a decision-making tool for management and control of eutrophication, suggests a breakdown in communication between researchers and water managers. Finally, corresponding management strategies are recommended, and the classification system can be used to simplify management by grouping lakes that may be managed by similar strategies. The classification management may enlighten and guide the appropriate policy implementation for lake eutrophication management.

      PubDate: 2016-08-10T11:13:00Z
       
  • The impact of land use change on water balance in Zhangye city, China
    • Abstract: Publication date: Available online 27 June 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Zhongxiao Sun, Feng Wu, Chenchen Shi, Jinyan Zhan
      Land use change has a significant effect on water balance, especially in arid region, such as Northwest China. In this paper, we analyze the effect of land use change on water balance in terms of the amount of water supply and demand from economic perspective. It's the first time to extend the basic 48 sectors input-output table to include water and land accounts that involved into multiple production processes for Zhangye city. We then perform the improved ORANI-G model, a single region Computable General Equilibrium (CGE) model, to analyze the effect of land use change on water balance under three scenarios. Subsequently, scenario-based simulation results are interpreted through selected sectors from agricultural, industrial, and service sectors respectively. Finally, the effect of land use change on water balance is analyzed through the difference between business-as-usual and land use unchanged scenarios. The results show that the extent of effect on water balance is different among sectors. Specifically, from the perspective of absolute value, service sectors are the largest, followed by industrial sectors, and the agricultural sectors are the least. Conversely, in terms of percentage change of land use, the largest extent of effect occurs in agricultural sectors. Additionally, with the rapid urbanization and the development of social economy, water balance in industrial sectors and service sectors will be stricken and reconstructed to a new high level. Simulation results also show that agricultural land shrinking will mitigate water scarcity distinctly, which indicates that balance the relationship among different stakeholders is imperative to guarantee water transformation from agricultural sectors to industrial and service sectors.

      PubDate: 2016-08-10T11:13:00Z
       
  • Long time-series spatiotemporal variations of NPP and water use efficiency
           in the Lower Heihe River Basin with serious water scarcity
    • Abstract: Publication date: Available online 27 June 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Haiming Yan, Jinyan Zhan, Huicai Yang, Fan Zhang, Guofeng Wang, Wenjie He
      It is of great significance to analyze the long time-series spatiotemporal dynamics of water use efficiency (WUE) to formulating appropriate management measures in response to the growing water scarcity in arid and semi-arid regions. This study analyzed the long time-series variations of WUE in the Lower Heihe River Basin, a typical arid and semi-arid region in China. The net primary productivity (NPP) was first estimated with the C-fix model, then WUE during 2001-2010 was calculated with the NPP and evapotranspiration (ET) data, and the accumulative WUE was further calculated. The results showed that the annual NPP and WUE in the study area ranged from zero to 448.70 gC/(m2•a) and from zero to 2.20 gC kg−1 H2O, respectively, both of which showed an overall increasing trend during 2001-2010. Besides, the spatial pattern of WUE kept overall unchanged during 2001-2010, but with remarkable change in some part of the study area. In addition, the accumulative WUE of the whole study area showed a first sharply decreasing and then gradually increasing trend, but there was still some scope to improve the WUE, and it is necessary to carry out some more specific policies to further improve the water allocation and WUE within the Lower Heihe River Basin. Although with some uncertainties, these results still can provide valuable reference information for improving the water resource management and ecological conservation to guarantee provision of essential ecosystem services in arid and semi-arid regions.

      PubDate: 2016-08-10T11:13:00Z
       
  • Allocating agricultural production factors: a scenario-based modeling of
           wheat production in Shandong Province, China
    • Abstract: Publication date: Available online 27 June 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Fan Zhang, Jinyan Zhan, Qian Zhang, Haiming Yan, Zhongxiao Sun
      We aim to determine the effects of agricultural factors input per hectare on wheat production, and to optimize the allocation of wheat production factors under three scenarios and in different operating modes. Data were collected from 204 farming households using a face-to-face questionnaire. The sampled farms were selected through a stratified random sampling technique. We find fertilizer cost, irrigation cost and machinery cost all positively and significantly affect the per-unit-area wheat production, indicating the labor cost is not the major driving factor on wheat yield increment. Multi-object optimization model is used to allocate the production factors per hectare. We find under the Business as usual (BAU) scenario, the irrigation cost per-hectare wheat production after optimization in 2014 grows at a rate of 24.31% and accounts for 14.9% of total input. Under the Cooperate Environmental Sustainability (CES) scenario, the fertilizer and pesticide costs after optimization drop significantly by 42.83% and 21.41%, respectively. Under the Rapid Benefit Growth (RBG) scenario, the irrigation cost after optimization increase by 2.56% and the fertilizer cost increases by 4.69% compared with the surveyed data. Comparison of optimized data among three operating modes shows that the labor costs at household farm and cooperative farm both increase significantly. Cooperative farms are more successful in production factor use efficiency and economic performance. In conclusion, wheat production at different operating modes could be improved so as to constitute more efficient and economic use of production factors.

      PubDate: 2016-08-10T11:13:00Z
       
  • Shear-tensile crack as a tool for reliable estimates of the
           non-double-couple mechanism: West Bohemia-Vogtland earthquake 1997 swarm
    • Abstract: Publication date: Available online 29 June 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Jan Šílený, Josef Horálek
      Shear-tensile crack is a model for an earthquake mechanism that is more constrained than the moment tensor but that can still describe a non-shear focus. As such, the shear-tensile crack model is more robust than the moment tensor model and yields more reliable estimates for the earthquake mechanism. Such an advantage verifies the credibility of the non-double-couple component found for some events of the 1997 West Bohemia-Vogtland earthquake swarm. As expected, in several cases, a significantly resolved non-double-couple component was obtained where the moment tensor approach failed. Additionally, for non-shear sources, the shear-tensile crack model offers optimization of the Poisson number within the focus, concurrently with retrieval of the mechanism. However, results obtained for the joint inversion of the 1997 swarm indicate that resolution is low. A series of synthetic experiments indicated that limited observations during 1997 were not the cause. Rather, hypothetical experiments of both very good and extremely poor network configurations similarly yielded a low resolution for the Poisson number. Applying this method to data for recent swarms is irrelevant because the small non-double-couple components detected within the inversion are spurious and, thus, the events are pure double-couple phenomena.

      PubDate: 2016-08-10T11:13:00Z
       
  • S-wave velocity measurement and the effect of basin geometry on site
           response, east San Francisco Bay area, California, USA
    • Abstract: Publication date: Available online 22 July 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Koichi Hayashi, Mitchell Craig
      We measured S-wave velocity profiles at eleven sites in the east San Francisco Bay area using surface wave methods. Data acquisition included multichannel analysis of surface waves using an active source (MASW), a passive surface-wave method using a linear array of geophones (Linear-MAM), and a two-station spatial autocorrelation method (2ST-SPAC) using long-period accelerometers. Maximum distance between stations ranged from several hundred meters to several kilometers, depending on the site. Minimum frequency ranged from 0.2 to 2 Hz, depending on the site, corresponding to maximum wavelengths of 10 to 1 km. Phase velocities obtained from three methods were combined into a single dispersion curve for each site. A nonlinear inversion was used to estimate S-wave velocity profiles to a depth of 200–2000 m, depending on the site. Resultant S-wave velocity profiles show significant differences among the sites. On the west side of the Hayward fault and the east side of the Calaveras fault, there is a low velocity layer at the surface, with S-wave velocity less than 700 m/s, to a depth of approximately 100 m. A thick intermediate velocity layer with S-wave velocity ranging from 700 to 1500 m/s lies beneath the low velocity layer. Bedrock with S-wave velocity greater than 1500 m/s was measured at depths greater than approximately 1700 m. Between the Hayward Fault and the Calaveras Fault, thicknesses of the low velocity layer and the intermediate velocity layer are less than 50 m and 200 m respectively, and depth to bedrock is less than 250 m. To evaluate the effect of a lateral change in bedrock depth on surface ground motion due to an earthquake, a representative S-wave velocity cross section perpendicular to the Hayward fault was constructed and theoretical amplification was calculated using a viscoelastic finite-difference method. Calculation results show that the low frequency (0.5–5 Hz) component of ground motion is locally amplified on the west side of the Hayward fault because of the effect of two-dimensional structure.

      PubDate: 2016-08-10T11:13:00Z
       
  • The Sustainability of Drinking Water Supply in Rural China: Does the
           Provision of Drinking Water Investment Mismatch the Demand of Residents?
    • Abstract: Publication date: Available online 27 July 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Ying Liu, Tang Yao, Yu Liu
      It is doubted that the top down nature of investment planning may lead to mismatches between drinking water investment and the demands of local residents in rural China. Statistical and econometric analysis based on data of 2020 rural households from five Chinese provinces from 1998 to 2011 are used to illustrate the linkage between demand for drinking water investment and construction of drinking water projects. Household’s demand significantly affects drinking water projects implemented by upper level governments and implemented jointly, but is not significant in explaining the projects implemented by village. There is evidence to suggest that the demands of local leaders override those of households in the implementation of drinking water projects provided by village in the early stage of 2005-2008. The situation improves in the latter stage of 2008-2011when the village level participatory bodies begin to provide opportunities for households to voice their preferences on public goods investment. The results of this study imply that it is important to explore appropriate regulations and policies that enabling local cadres to better meet local demands of their communities to ensure the sustainability of rural drinking water supply.

      PubDate: 2016-08-10T11:13:00Z
       
  • Seismic amplification in a fractured rock site. The case study of San
           Gregorio (L'Aquila, Italy)
    • Abstract: Publication date: Available online 6 August 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Di Naccio Deborah, Vassallo Maurizio, Di Giulio Giuseppe, Amoroso Sara, Cantore Luciana, Hailemikael Salomon, Falcucci Emanuela, Gori Stefano, Giuliano Milana
      The village of San Gregorio (SG), eight kilometres away from L’Aquila (central Italy), was severely damaged by the April 6, 2009 L’Aquila earthquake (MW 6.1). A coseismic fracture zone was mapped along SW-dipping fault segments crossing SG, which is situated at the base of a carbonate relief bounded by the Aterno river alluvial plain. An interdisciplinary approach was used to investigate the seismic response of the area based on geological-structural, geophysical and seismic analyses. We integrated our data with available information from the recent microzonation studies. SG is partly built on alluvial fan deposits constituted by cemented gravel, and partly on jointed carbonate bedrock. An extensive survey of noise measurements showed strong and polarized peaks in the horizontal-to-vertical spectral ratios (H/V), both on soft and rock sites in the 2-10 Hz frequency band. Further, we checked the stability with time of H/V ratios at three sites of SG. An analysis on local earthquakes confirmed the results of noise measurements. To understand the influence of rock mass jointing condition on site effects, we performed structural surveys on carbonate bedrock. We also evaluated the propagation velocities at rock sites using seismic active and seismic dilatometer test (SDMT) surveys. Our analysis showed low values of compressional (V P ) and shear wave (V S ) velocities of the outcropping rock, where we also observed strong H/V spectral peak and high-density rock fracturing.

      PubDate: 2016-08-10T11:13:00Z
       
  • Regionalization of Europe based on a K-Means Cluster Analysis of the
           climate change of temperatures and precipitation
    • Abstract: Publication date: Available online 24 May 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): M.J. Carvalho, P. Melo-Gonçalves, J.C. Teixeira, A. Rocha
      In order to study climate change on a regional scale using Earth System Models, it is useful to partition the spatial domain into regions according to their climate changes. The aim of this work is to divide the European domain into regions of similar projected climate changes using a simulation of daily total precipitation, minimum and maximum temperatures for the recent-past (1986–2005) and long-term future (2081–2100) provided by the Coupled Model Intercomparison Project (CMIP5). The difference between the long-term future and recent-past daily climatologies of these three variables is determined. Aiming to objectively identify the grid points with coherent climate changes, a K-Mean Cluster Analysis is applied to these differences. This method is performed for each variable independently (univariate version) and for the aggregation of the three variables (multivariate version). A mathematical approach to determine the optimal number of clusters is pursued. However, due to the method characteristics, a sensitivity test to the number of clusters is performed by analysing the consistency of the results. This is a novel method, allowing for the determination of regions based on the climate change of multiple variables. Results from the univariate application of this method are in accordance with results found in the literature, showing overall similar regions of changes. The regions obtained for the multivariate version are mainly defined by latitude over European land, with some features of land-sea interaction. Furthermore, all regions have statistically different distributions of at least one of the variables, providing confidence to the regions obtained.

      PubDate: 2016-06-15T15:51:38Z
       
  • Robust inferences on climate change patterns of precipitation extremes in
           the Iberian Peninsula
    • Abstract: Publication date: Available online 1 June 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Paulo de Melo-Gonçalves, Alfredo Rocha, João Santos
      This work presents a methodology to make statistical significant and robust inferences on climate change from an ensemble of model simulations. This methodology is used to assess climate change projections of the Iberian daily-total precipitation for a near-future (2021 – 2050) and a distant-future (2069 – 2098) climates, relatively to a reference past climate (1961 – 1990). Climate changes of precipitation spatial patterns are estimated for annual and seasonal values of: (i) total amount of precipitation (PRCTOT), (ii) maximum number of consecutive dry days (CDD), (iii) maximum of total amount of 5-consecutive wet days (Rx5day), and (iv) percentage of total precipitation occurred in days with precipitation above the 95 t h percentile of the reference climate (R95T). Daily-total data were obtained from the multi-model ensemble of fifteen Regional Climate Model simulations provided by the European project ENSEMBLES. These regional models were driven by boundary conditions imposed by Global Climate Models that ran under the 20C3M conditions from 1961 to 2000, and under the A1B scenario, from 2001 to 2100, defined by the Special Report on Emission Scenarios of the Intergovernmental Panel on Climate Change. Non-parametric statistical methods are used for significant climate change detection: linear trends for the entire period (1961 – 2098) estimated by the Theil-Sen method with a statistical significance given by the Mann-Kendall test, and climate-median differences between the two future climates and the past climate with a statistical significance given by the Mann-Whitney test. Significant inferences of climate change spatial patterns are made after these non-parametric statistics of the multi-model ensemble median, while the associated uncertainties are quantified by the spread of these statistics across the multi-model ensemble. Significant and robust climate change inferences of the spatial patterns are then obtained by building the climate change patterns using only the grid points where a significant climate change is found with a predefined low uncertainty. Results highlight the importance of taking into account the spread across an ensemble of climate simulations when making inferences on climate change from the ensemble-mean or ensemble-median. This is specially true for climate projections of extreme indices such CDD and R95T. For PRCTOT, a decrease in annual precipitation over the entire peninsula is projected, specially in the north and northwest where it can decrease down to 400 mm by the middle of the 21st century. This decrease is expected to occur throughout the year except in winter. Annual CDD is projected to increase till the middle of 21st century overall the peninsula, reaching more than three weeks in the southwest. This increase is projected to occur in summer and spring. For Rx5day, a decrease is projected to occur during spring and autumn in the major part of the peninsula, and during summer in northern Iberia. Finally, R95T is projected to decrease around 20% in northern Iberia in summer, and around 15% in the south-southwest in autumn.

      PubDate: 2016-06-15T15:51:38Z
       
  • Managing ground and surface water resources using innovative methods in
           rural and urban areas of Sub-Saharan Africa
    • Abstract: Publication date: June 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 93
      Author(s): Benjamin Mapani, Lapologang Magole, Hodson Makurira, Dominic Mazvimavi, Maideyi Meck, Maloes Mul


      PubDate: 2016-06-15T15:51:38Z
       
  • A new approach for computing a flood vulnerability index using cluster
           analysis
    • Abstract: Publication date: Available online 22 April 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Paulo Fernandez, Sandra Mourato, Madalena Moreira, Luísa Pereira
      A Flood Vulnerability Index (FloodVI) was developed using Principal Component Analysis (PCA) and a new aggregation method based on Cluster Analysis (CA). PCA simplifies a large number of variables into a few uncorrelated factors representing the social, economic, physical and environmental dimensions of vulnerability. CA groups areas that have the same characteristics in terms of vulnerability into vulnerability classes. The grouping of the areas determines their classification contrary to other aggregation methods in which the areas’ classification determines their grouping. While other aggregation methods distribute the areas into classes, in an artificial manner, by imposing a certain probability for an area to belong to a certain class, as determined by the assumption that the aggregation measure used is normally distributed, CA does not constrain the distribution of the areas by the classes. FloodVI was designed at the neighbourhood level and was applied to the Portuguese municipality of Vila Nova de Gaia where several flood events have taken place in the recent past. The FloodVI sensitivity was assessed using three different aggregation methods: the sum of component scores, the first component score and the weighted sum of component scores. The results highlight the sensitivity of the FloodVI to different aggregation methods. Both sum of component scores and weighted sum of component scores have shown similar results. The first component score aggregation method classifies almost all areas as having medium vulnerability and finally the results obtained using the CA show a distinct differentiation of the vulnerability where hot spots can be clearly identified. The information provided by records of previous flood events corroborate the results obtained with CA, because the inundated areas with greater damages are those that are identified as high and very high vulnerability areas by CA. This supports the fact that CA provides a reliable FloodVI.

      PubDate: 2016-04-24T13:42:01Z
       
  • Assessing the feasibility of integrating remote sensing and in-situ
           
    • Abstract: Publication date: Available online 22 April 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): S. Dlamini, I. Nhapi, W. Gumindoga, T. Nhiwatiwa, T. Dube
      This work investigates the likelihood of integrating the cheap and readily-available broadband multispectral MODIS data and in-situ measurements in quantifying and monitoring water quality status of an inland lake within Upper Manyame Catchment in Zimbabwe. Specifically we used MODIS images to quantify inland lake chlorophyll_a concentrations, as a proxy for predicting lake pollution levels. The findings of this study show a high chlorophyll_a concentration of 0.101±0.128 μg/L within the Lake. The results further demonstrated that the chlorophyll_a concentration levels did not significantly vary (p = 0.788) between sites, except among depths (p=0.05). Further, prediction results based on the relationship between observed and predicted chlorophyll_a produced a high R2 value of 0.89 and a root mean square error (RMSE) value of 0.003 μg/L. Moreover, the derived landuse maps of Upper Manyame Catchment indicated a significant variation in the percentage settlement in 1985, 1994 and 2010 change from 1985 to 2010. For instance, 8% increase in settlement in the period between 1994 and 2010 and over 12% increase from 1985 to 2010 and a decline in percent forest coverage (i.e. 9.8% in 1985 to 2.0% in the year 2010) in the catchment was observed. Overall, the findings of this study highlights the importance of free and readily-available satellite datasets (such as the multispectral MODIS and Landsat) in quantifying and monitoring water quality across inland lakes especially in data-scarce areas like Sub-Saharan Africa.

      PubDate: 2016-04-24T13:42:01Z
       
  • Application of satellite products and hydrological modeling for flood
           early warning
    • Abstract: Publication date: Available online 19 March 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Sifan A. Koriche, Tom H.M. Rientjes
      Floods have caused devastating impacts to the environment and society in Awash River Basin, Ethiopia. Since flooding events are frequent, this marks the need to develop tools for flood early warning. In this study, we propose a satellite based flood index to identify the runoff source areas that largely contribute to extreme runoff production and floods in the basin. Satellite based products used for development of the flood index are CMORPH (0.250 by 0.250, daily) product for calculation of the Standard Precipitation Index (SPI) and a SRTM digital elevation model for calculation of the Topographic Wetness Index (TWI). Other satellite products used in this study are for rainfall-runoff modelling to represent rainfall, potential evapotranspiration, vegetation cover and topography. Results of the study show that assessment of spatial and temporal rainfall variability by satellite products may well serve in flood early warning. Preliminary findings on effectiveness of the flood index developed in this study indicate that the index is well suited for flood early warning. The index combines SPI and TWI, and preliminary results illustrate the spatial distribution of likely runoff source areas that cause floods in flood prone areas.

      PubDate: 2016-03-20T19:09:57Z
       
  • The hydrology of sand rivers in Zimbabwe and the use of remote sensing to
           assess their level of saturation
    • Abstract: Publication date: Available online 10 March 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): S.C. Mpala, A.S. Gagnon, M.G. Mansell, S.W. Hussey
      Sand rivers are ephemeral watercourses containing sand that are occasionally flooded with rainwater runoff during the rainy season. Although the riverbed appears dry for most of the year, there is perennial groundwater flow within the sand. This water flowing beneath the surface is a valuable resource for local communities; nonetheless our understanding of such river systems is limited. Hence, this paper aims to improve our understanding of the hydrology of sand rivers and to examine the potential use of remote sensing to detect the presence of water in the sand. The relationship between rainfall events and changes in the water level of two sand rivers in the Matabeleland South Province of Zimbabwe was investigated. A lagged relationship was observed for the Manzamnyama River but for the Shashani River the relationship was seen only when considering cumulative rainfall events. The comparison of the modelled flow as simulated by a water balance model with observations revealed the important influence of the effective sediment depth on the recharge and recession of the alluvial channels in addition to the length of the channel. The possibility of detecting water in the alluvial sands was investigated using remote sensing. During the wet season, optical images showed that the presence of water on the riverbed was associated with a smooth signal, as it tends to reflect the incident radiation. A chronological analysis of radar images for different months of the year demonstrates that it is possible to detect the presence of water in the sand rivers. These results are a first step towards the development of a methodology that would aim to use remote sensing to help reducing survey costs by guiding exploratory activities to areas showing signs of water abstraction potential.

      PubDate: 2016-03-11T18:23:31Z
       
 
 
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