scholarly journals Modelling of channel transmission loss processes in semi-arid catchments of southern Africa using the Pitman Model

2018 ◽  
Vol 378 ◽  
pp. 17-22 ◽  
Author(s):  
Vuyelwa Mvandaba ◽  
Denis Hughes ◽  
Evison Kapangaziwiri ◽  
Jean-Marc Mwenge Kahinda ◽  
Nadia Oosthuizen
Keyword(s):  
Southern Africa ◽  
Arid Regions ◽  
Transmission Loss ◽  
Hydrological Process ◽  
Transmission Losses ◽  
Sustainable Resource Management ◽  
Societal Issues ◽  
The Impact ◽  
Semi Arid

Abstract. Water availability is one of the major societal issues facing the world. The ability to understand and quantify the impact of key hydrological processes, on the availability of water resources, is therefore integral to ensuring equitable and sustainable resource management. Channel transmission losses are an “under-researched” hydrological process that affects resource availability in many semi-arid regions such as the Limpopo River Basin in southern Africa, where the loss processes amount to approximately 30 % of the water balance. To improve the understanding of these loss processes and test the capability of modelling routines, three approaches using the Pitman model are applied to selected alluvial aquifer environments. The three approaches are an explicit transmission loss function, the use of a wetland function to represent channel-floodplain storage exchanges and the use of a “dummy” reservoir to represent floodplain storage and evapotranspiration losses. Results indicate that all three approaches are able to simulate channel transmission losses with differing impacts on the regional flows. A determination of which method best represents the channel transmission losses process requires further testing in a study area that has reliable observed historical records.

Investigating the possible measure to protect groundwater from polluted streams in Arid and Semi-Arid Regions: the Eastern Nile Delta case study

2021 ◽  
Author(s):  
Ismail Abd-Elaty ◽  
Martina Zelenakova ◽  
Salvatore Straface ◽  
Zuzana Vranayová ◽  
Mohamed Abu-hashim ◽  
...  
Keyword(s):  
Drinking Water ◽  
Arid Regions ◽  
Nile Delta ◽  
Total Dissolved Solids ◽  
Polluted Water ◽  
Deep Aquifer ◽  
Lower Permeability ◽  
The Impact ◽  
Semi Arid

<p>Groundwater is the main source of drinking water in the Nile Delta. Unfortunately, it might be polluted by seepage from polluted streams. This study was carried out to investigate the possible measures  to  protect groundwater  in the Nile delta aquifer using a numerical model (MT3DMS - Mass Transport 3-Dimension Multi-Species). The sources of groundwater contamination were identified and the total dissolved solids (TDS) was taken as an indicator for the contamination. Different strategies were investigated for mitigating the impact of polluted water: i) allocating polluted drains and canals in lower permeability layers; ii)  installing cut-off walls in the polluted drains, and finally, iii) using lining materials in polluted drains and canals. Results indicated these measures effective to mitigate the groundwater pollution. In particular, the cut-off wall was effective for contamination reduction in shallow aquifers, whereas it had no effect in the deep aquifer, while lining materials in polluted drains and canals were able to prevent contamination and to protect the freshwater in the aquifers.  It is worth mentioning that this study was partially supported by a bilateral project between ASRT (Egypt) and CNR (Italy).</p><p> </p><p> </p>

scholarly journals Sensitivity of Maize Yield in Smallholder Systems to Climate Scenarios in Semi-Arid Regions of West Africa: Accounting for Variability in Farm Management Practices

Agronomy ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 639 ◽  
Author(s):  
Bright Freduah ◽  
Dilys MacCarthy ◽  
Myriam Adam ◽  
Mouhamed Ly ◽  
Alex Ruane ◽  
...  
Keyword(s):  
Climate Change ◽  
Arid Regions ◽  
Climate Models ◽  
Smallholder Farmers ◽  
Maize Yield ◽  
Climate Scenarios ◽  
Relative Standard ◽  
The Impact ◽  
Semi Arid ◽  
Smallholder Systems

Climate change is estimated to exacerbate existing challenges faced by smallholder farmers in Sub-Sahara Africa. However, limited studies quantify the extent of variation in climate change impact under these systems at the local scale. The Decision Support System for Agro-technological Transfer (DSSAT) was used to quantify variation in climate change impacts on maize yield under current agricultural practices in semi-arid regions of Senegal (Nioro du Rip) and Ghana (Navrongo and Tamale). Multi-benchmark climate models (Mid-Century, 2040–2069 for two Representative Concentration Pathways, RCP4.5 and RCP8.5), and multiple soil and management information from agronomic surveys were used as input for DSSAT. The average impact of climate scenarios on grain yield among farms ranged between −9% and −39% across sites. Substantial variation in climate response exists across farms in the same farming zone with relative standard deviations from 8% to 117% at Nioro du Rip, 13% to 64% in Navrongo and 9% to 37% in Tamale across climate models. Variations in fertilizer application, planting dates and soil types explained the variation in the impact among farms. This study provides insight into the complexities of the impact of climate scenarios on maize yield and the need for better representation of heterogeneous farming systems for optimized outcomes in adaptation and resilience planning in smallholder systems.

scholarly journals A Review of the Impacts of Roads on Wildlife in Semi-Arid Regions

Diversity ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 81 ◽  
Author(s):  
W. Richard J. Dean ◽  
Colleen L. Seymour ◽  
Grant S. Joseph ◽  
Stefan H. Foord
Keyword(s):  
Genetic Diversity ◽  
Arid Regions ◽  
Vocal Communication ◽  
Traffic Noise ◽  
Noise Pollution ◽  
Mitigation Measures ◽  
Obvious Effect ◽  
Long Term Impact ◽  
The Impact ◽  
Semi Arid

Roads now penetrate even the most remote parts of much of the world, but the majority of research on the effects of roads on biota has been in less remote temperate environments. The impacts of roads in semi-arid and arid areas may differ from these results in a number of ways. Here, we review the research on the impacts of roads on biodiversity patterns and ecological and evolutionary processes in semi-arid regions. The most obvious effect of roads is mortality or injury through collision. A diversity of scavengers are killed whilst feeding on roadkill, a source of easily accessed food. Noise pollution from roads and traffic interferes with vocal communication by animals, and birds and frogs living along noisy roads compensate for traffic noise by increasing the amplitude or pitch of their calls. Artificial light along roads impacts certain species’ ability to navigate, as well as attracting invertebrates. Animals are in turn attracted to invertebrates at streetlights, and vulnerable to becoming roadkill themselves. Genetics research across taxa confirms a loss of genetic diversity in small populations isolated by roads, but the long-term impact on the fitness of affected populations through a reduction in genetic diversity is not yet clear. Roads may rapidly cause genetic effects, raising conservation concerns about rare and threatened species. We assess mitigation measures and collate methods to identify the impact of roads on wildlife populations and their associated ecosystems, with a particular focus on recent advances.

Impact of surface roughness on dust occurrence frequency over arid regions

2021 ◽  
Author(s):  
Martina Klose ◽  
Carlos Pérez García-Pando ◽  
Paul Ginoux ◽  
Ron L. Miller
Keyword(s):  
Surface Roughness ◽  
Spatial Patterns ◽  
Arid Regions ◽  
Transport Model ◽  
Dust Emission ◽  
Occurrence Frequency ◽  
Dust Transport ◽  
Drag Partition ◽  
The Impact ◽  
Semi Arid

<p>Soil dust aerosol created by wind erosion of arid and semi-arid surfaces dominates climate effects over large areas of the Earth. To represent the dust cycle, Global Earth System Models (ESMs) typically prescribe preferential dust sources phenomenologically using empirical source scaling functions. While this approach has helped to compensate for a lack or inaccuracy of soil and surface input data to models, it potentially limits progress in the representation of the global dust cycle, because such strong empirical constraints make models less sensitive to parameters known to affect dust emission, and thus potentially insensitive to changes in climate. Here we investigate the link between surface roughness due to non-erodible elements such as vegetation, pebbles and rocks, and the spatial patterns of dust activity. Using two different satellite-based methods to represent roughness within an atmospheric dust transport model, we evaluate the impact of surface roughness on the spatial distribution of dust optical depth occurrence frequency observed from satellite by both reducing the atmospheric momentum available for particle entrainment and protecting the surface from dust emission. We test the variability of our results across conceptually different parameterizations of dust emission and drag partition. Our results suggest that the spatial patterns of dust activity are largely determined by surface roughness, not only in semi-arid, but also in arid regions, where green vegetation is sparse or absent. </p>

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