Shallow groundwater in the Atankwidi Catchment of the White Volta Basin: current status and future sustainability

Shallow groundwater in the Atankwidi Catchment of the White Volta Basin: current status and future sustainability
Author: Barry, Boubacar
Publisher: IWMI
Total Pages: 34
Release: 2010
Genre:
ISBN: 9290907371

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The Atankwidi Catchment, which lies in the White Volta Basin in West Africa, is intensively cultivated by locals for economic gains. During dry seasons, farmers irrigate their crops, chiefly tomatoes, using shallow groundwater harvested from shallow ponds they dig using simple tools like an axe, hoe, bucket and bowls. Recent expansion in cultivated areas has brought to the fore the need to estimate the volume of shallow groundwater stored in the catchment’s underlying aquifer and to what extent it can sustain the incremental growth in irrigated areas.

Smallholder shallow groundwater irrigation development in the upper east region of Ghana

Smallholder shallow groundwater irrigation development in the upper east region of Ghana
Author:
Publisher: IWMI
Total Pages: 40
Release: 2011
Genre:
ISBN: 9290907479

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In sub-Saharan Africa, there is paucity of information on the potential of groundwater resources. The limited available information paints a pessimistic view about groundwater resources. Due to its perceived inadequate availability, groundwater is associated with domestic use but the potential for using it for agriculture is not well reflected in the national irrigation policies. Contrary to official pessimism, farmers do use groundwater for agriculture in many countries of sub-Saharan Africa including Ghana. This paper analyzes the current extent of use, economics, socioeconomic impacts, and constraints and opportunities of shallow groundwater irrigation based on the experiences of smallholders in the three micro-watersheds of the White Volta Basin in the Upper East Region of Ghana.

Development of a water balance for the Atankwidi catchment, West Africa - A case study of groundwater recharge in a semi-arid climate

Development of a water balance for the Atankwidi catchment, West Africa - A case study of groundwater recharge in a semi-arid climate
Author:
Publisher: Cuvillier Verlag
Total Pages: 184
Release: 2006-05-31
Genre: Science
ISBN: 3736918852

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Regolith aquifers in the weathered zone overlying Precambrian basement rocks serve as the main source of groundwater in a large part of the Volta River basin in West Africa. A prerequisite for sustainable groundwater resources management is the knowledge of recharge processes and the annual recharge rate. This research assesses the water balance, and in particular the groundwater recharge rate, for the Atankwidi catchment, a 275 km² sub-catchment of the White Volta in northern Ghana. Large uncertainties are typically inherent in any singular method to determine groundwater recharge. For this reason, an integrated approach is developed in this work which makes use of several field methods and combines results from these methods with water budget modeling. Field methods included in this approach are groundwater level observations, isotope analyses and a Chloride mass balance. The Atankwidi catchment falls within the semi-arid Sudan-Savanna climate zone. The climate is characterized by high temperatures and a single rainy season from May to October with an average annual rainfall of 990 mm. The hydrogeological system consists of three aquifers: The discontinuous, shallow aquifer, the regolith aquifer and the fracture aquifer. The principal aquifer is the regolith aquifer in the weathered mantle, which is usually targeted for drinking water supply. It forms a continuous aquifer with an average saturated thickness of 25 m and a hydraulic conductivity of 2.5E-6 to 2.5E-5 m/s. Recharge rates vary considerably between wet and dry years and between locations, with a range of 2 % to 13 % of annual rainfall. The long term recharge rate is determined by the Chloride mass balance to be approximately 6 % of average annual rainfall. The research emphasizes the importance of high rainfall intensities in creating groundwater recharge. Interannual comparison of water level fluctuations shows that a decrease in annual rainfall of 20 % causes a reduction of groundwater recharge of 30 % to 60 %. The impact of changing quantities of annual rainfall on groundwater recharge is overestimated by methods that do not account for infiltration by preferential flow. A long term average groundwater recharge of 60 mm/y compares to a total current groundwater abstraction of 4 mm/y in the study area, which is one of the areas with the highest groundwater use per km² in the Volta River basin. Recharge is therefore currently not a limiting factor for groundwater resources development. Water budget modeling using WaSIM-ETH calculates that 63 % of annual rainfall is lost to evapotranspiration in a wet year (2003), and 82 % in a dry year (2004). In the investigated mesoscale catchment 23 % and 11 % of annual rainfall end up as surface run-off in a wet year and a dry year, respectively. Approximately 40 % of surface run-off consists of interflow, while the main fraction is direct run-off. Base flow from groundwater is negligible. Groundwater flow in the regolith aquifer is modeled with Visual Modflow, assuming average hydraulic conductivities as determined by pumping test evaluation. The model calculatesthat only about 5 % of groundwater recharge leaves the basin as groundwater flow. This is evidence that the regolith aquifer does not contribute to a large extent to regional groundwater flow. Leakage to localized zones of high hydraulic conductivity of the fracture aquifer, which underlies the regolith aquifer, could act as a main sink of groundwater recharge. However, the exact location and hydraulic properties of fracture zones are largely unknown, so that the flux from the regolith aquifer to these fractures as well as the amount of flow through fractures is impossible to estimate at present. Pumping tests with observation wells to assess the specific yield, long-term pumping test at the basin outlet and a continuation of groundwater hydrograph recording at high temporal resolution could largely enhance the knowledge of hydraulic properties in the future. The groundwater model could then be improved and extended to gain certainty on the characteristics of groundwater flow.

The Water Resource Implications of Changing Climate in the Volta River Basin

The Water Resource Implications of Changing Climate in the Volta River Basin
Author: Matthew McCartney
Publisher: IWMI
Total Pages: 46
Release: 2012
Genre:
ISBN: 9290907649

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The Volta River is one of the major rivers in Africa. In this study, a dynamic regional climate model (CCLM), a hydrological model (SWAT) and a water resource model (WEAP) were used to provide an assessment of one downscaled ‘middle impact’ climate change scenario on the performance of existing and planned irrigation and hydropower schemes. The results indicate that, by the middle of the twenty-first century, altered climate is likely to undermine the technical performance of existing and planned reservoirs, which will, in turn, affect development outcomes. Future water resources development in the basin requires interventions that bolster resilience and water security. Much more systematic planning of water storage, greater cooperation between the riparian states and consideration of innovative approaches to water storage are needed.

The Volta River Basin

The Volta River Basin
Author: Timothy O. Williams
Publisher: Routledge
Total Pages: 376
Release: 2016-09-19
Genre: Nature
ISBN: 131747953X

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The Volta River Basin (VRB) is an important transboundary basin in West Africa that covers approximately 410,000 square kilometres across six countries: Benin, Burkina Faso, Côte d’Ivoire, Ghana, Mali and Togo. Its natural resources sustain the livelihoods of its population and contribute to economic development. This book provides a comprehensive, interdisciplinary review and assessment of the issues and challenges faced. The authors provide a science-based assessment of current and future scenarios of water availability, the demands of key sectors, including agriculture and hydropower, and the environment under changing demographic, economic, social and climatic conditions. They also identify solutions and strategies that will allow available water resources to be sustainably used to improve agricultural productivity, food security and economic growth in the VRB. Overall, the work examines from a multidisciplinary and multi-stakeholder perspective the solutions and strategies to improve the use of water and other natural resources in the VRB to achieve enhanced food security, livelihoods and economic growth.

Sustainable Use of Soils and Water

Sustainable Use of Soils and Water
Author: Fernando António Leal Pacheco
Publisher: MDPI
Total Pages: 332
Release: 2020-04-30
Genre: Science
ISBN: 3039286447

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This book on the sustainable use of soils and water addressed a variety of issues related to the utopian desire for environmental sustainability and the deviations from this scene observed in the real world. Competing interests for land are frequently a factor in land degradation, especially where the adopted land uses do not conform with the land capability (the natural use of soil). The concerns of researchers about these matters are presented in the articles comprising this Special Issue book. Various approaches were used to assess the (im)balance between economic profit and environmental conservation in various regions, in addition to potential routes to bring landscapes back to a sustainable status being disclosed.

The Impacts of Water Infrastructure and Climate Change on the Hydrology of the Upper Ganges River Basin

The Impacts of Water Infrastructure and Climate Change on the Hydrology of the Upper Ganges River Basin
Author: Luna Bharati
Publisher: IWMI
Total Pages: 40
Release: 2011
Genre:
ISBN: 9290907444

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This study assessed the variability of flows under present and ‘naturalized’ basin conditions in the Upper Ganges Basin (UGB). Furthermore, the PRECIS regional climate model (RCM) was used to generate climate projections for the UGB, with subsequent simulations of future river flows. Results show that the annual average precipitation, actual evapotranspiration (ET) and net water yields of the whole basin were 1,192 mm, 416 mm and 615 mm, respectively. Precipitation, ET and water yields were found to be higher in the forested and mountainous upper areas of the UGB. On an annual average, present-day flows throughout UGB are about 2-8% lower than under naturalized conditions. Dry and wet season flows under climate change (CC) scenario A2 are lower than that under present climate conditions at upstream locations, but higher at downstream locations of UGB. Flows under CC scenario B2 are systematically higher and lower than that under CC scenario A2 during dry and wet seasons, respectively.

An assessment of crop water productivity in the Indus and Ganges River Basins: current status and scope for improvement

An assessment of crop water productivity in the Indus and Ganges River Basins: current status and scope for improvement
Author: Cai, Xueliang
Publisher: IWMI
Total Pages: 34
Release: 2010
Genre:
ISBN: 9290907355

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The Indus and Ganges River Basin, being the most populous in the world, is under extreme pressure to sustain food security. Production resources including water are being exploited to various levels from underdevelopment to heavy overexploitation. This report provides a bird’s eye view of the basin and focuses on the nexus between agricultural production and water consumption, making it possible to pinpoint the areas with high/low water productivity and identify the factors behind this, which helps to promote informed decision making in light of environmental sustainability.

Water Productivity in Context

Water Productivity in Context
Author: Barker, R.
Publisher: IWMI
Total Pages: 37
Release: 2012
Genre:
ISBN: 9290907517

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As we enter an era of increasing water scarcity, there is a growing interest to find ways to capture and put water to more productive uses. Substantial increases in the productivity of water in agriculture are needed to meet the demands for food and ensure environmental security, and to satisfy the demands for non-agricultural uses. However, increasing water productivity in rice-dominated agriculture is a function of the irrigation infrastructure, advances in rice-plant breeding, and the physical, institutional and socioeconomic environments. This paper first describes the potential ways in which increased water productivity can be achieved in the context of rice production in Asia. It then illustrates the ways in which the differences in the environmental context affect the ability to increase water productivity, the approaches used and the incentives to do so. This is explained using two ‘case studies’ reflecting the experiences of Taiwan and the Philippines over the past half-century.

Urban wastewater and agricultural reuse challenges in India

Urban wastewater and agricultural reuse challenges in India
Author:
Publisher: IWMI
Total Pages: 40
Release: 2013-11-14
Genre: Nature
ISBN: 9290907657

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More than 1 million hectares of urban land in India could be irrigated for crops if wastewater was made safe for use. Lack of systematic data collection by municipalities makes it difficult to accurately assess the wastewater generation or estimate the total amount of urban area under wastewater irrigation, so the potential of urban and peri-urban farming could be even greater. This study attempted to analyze the current status of wastewater generation, its uses and livelihood benefits especially in agriculture, based on national data and case studies from Ahmedabad, New Delhi, Hyderabad, Kanpur and Kolkata.