Groundwater mapping and its implications for rural water supply coverage in Uganda

Groundwater plays a significant role in rural water supply but its development has been made with very little information on the hydrogeological conditions and groundwater potential of various areas of the country. This has not only resulted in unsuccessful water sources but also in resources being spent on very expensive water supply technologies when cheaper and more sustainable ones are possible. This in turn has affected government’s efforts to increase rural water supply coverage, which currently stands at 58 percent. In order to significantly improve water supply coverage in the country using low-cost, simple water-supply technologies, Uganda has initiated a Groundwater Mapping Programme to prepare maps representing groundwater resources in terms of their quantity and quality and summarizing this information spatially. Six different types of maps have been prepared all of which are important in guiding proper planning of groundwater development activities. Groundwater maps are guiding district political and technical officials on the most feasible water supply technology options to consider in various areas and are also providing them with indications of areas with low water supply coverage, which require more attention. The districts are now exclusively constructing shallow wells in areas where they are indicated as feasible as opposed to the past practice of construction deep boreholes everywhere. The people with the lowest water supply coverage are also using the maps to bargain for their equitable share of government resources. It is expected that with the availability of groundwater maps there will be a reduction in failure of wells and cost of water supply systems resulting in increase in water supply coverage and hence more benefit to the people

Regolith importance in groundwater development

Regolith importance in groundwater developmen

Groundwater resources management in urban areas of Uganda: experiences and challenges

Groundwater development for urban water supply has been ongoing since early 1990. In some urban areas however, groundwater is heavily abstracted resulting in lowering of groundwater levels and sometimes competitive pumping between water sources. The lack of sewerage systems in urban areas has also lead to construction of onsite sanitation systems in form of septic tanks and pit latrines, which have caused contamination of groundwater resources in many areas. Protection of groundwater in terms of quality and quantity is therefore needed to control overexploitation and pollution of groundwater. This requires undertaking studies to resolve key practical groundwater management questions in order to guide optimum groundwater development and determination of groundwater protections zones around boreholes in fractured rocks. Furthermore, an institutional framework for groundwater resources management combined with an adequate awareness raising programme on water resources management are required to enable the water users actively participate in groundwater management and protection

Need for reform of water resources management in Uganda

Need for reform of water resources management in Ugand

Groundwater flow and storage in weathered crystalline rock aquifer systems of Uganda

Groundwater is widely developed for town water supplies in weathered crystalline rocks in sub-Saharan Africa but the sustainability of this abstraction is unknown. Groundwater flow and storage in aquifers underlying two towns in central (Wobulenzi) and southwestern (Rukungiri) Uganda are assessed using environmental tracers and aquifer responses to hydraulic stress. Stable isotope ratios ( H: H, O: O) in precipitation and groundwater, the timely response of groundwater levels to bimodal rainfall, and short groundwater residence times of less than 22 years and big proportions of modern groundwater (5 to 100 %), derived from reconstructed atmospheric inputs of H and anthopogenic gases (CFC-113, CFC-12, CFC-11), clearly indicate active rainfall-fed, groundwater recharge. Diagnostic plots (s versus t/r , log-log, log-linear, derivative, flow dimension) of drawdown responses are used to inform conceptual models of groundwater flow. In Wobulenzi, linear flow through individual bedrock fractures at early pumping times (between 600 and 1500 minutes) is succeeded by radial flow through interconnected fractures that induce vertical flow in a thick weathered (regolith) aquifer at late pumping times (approximately 1800 minutes). Groundwater abstraction from bedrock fractures of 12 m h" per borehole, has not significantly affected groundwater storage over the last 9 years due to vertical leakage from overlying weathered aquifers that is commensurate to rainfall-fed recharge. In Rukungiri, a highly productive aquifer comprising coarse-grained, fluvial sediments, is identified in palaeochannels of former westerly flowing river networks. Fluvial sediments can feature significant thicknesses in palaeochannels of major river networks truncated by Miocene to Pleistocene rifting but subsequent erosion in the intra-arch basin, draining to the downfaulted rift floor significantly constrains the extent and thickness of the aquifers and, hence, the sustainability of groundwater abstraction. Depletion of groundwater storage over the last 8 years as a result of abstraction (12 m h" per borehole), is indicated by water-level declines of 2.5 m a". The identification of the palaeochannel aquifer provides new insight into the understanding of the relationship between the geomorphology and hydrogeology of deeply weathered environments and a new target for groundwater development in the humid tropics

Management of Ground Water in Africa Including Transboundary Aquifers: Implications for Food Security, Livelihood and Climate Change Adaptation

Groundwater is one of the most important sources for drinking water, livestock water, and irrigation in Africa. It is of vital importance in meeting the Millennium Development Goals (MDGs) target of accessing clean water, as most of rural Africa and a considerable part of urban Africa are supplied by groundwater. Groundwater also has a major role to play in improving food security through expansion of irrigation supplied by shallow and deep wells. As such, groundwater has high relevance to the development and wellbeing of Africa, if adequately assessed and sustainably exploited. However, impacts of rapid development and climate change on water resources, including groundwater, are expected to be very severe unless major actions are taken to address the limited human and institutional capacity and hydrogeological knowledge base needed to devise sustainable adaptive water management strategies. Whilst the potential for groundwater resources development and the extent of their vulnerability due to climate change in the African context continue to be reported in the literature, a quantitative understanding of these issues remains poor. Although groundwater systems respond to human and climatic changes slowly (relative to surface water systems), climate change still could affect groundwater significantly through changes in groundwater recharge as well as groundwater storage and utilization. These changes result from changes in temperature and precipitation or from change in land use/land cover, and increased demand. There is therefore a need for ensuring sustainability and proper management of groundwater resources through instituting proper aquifer management practices such as the establishment of groundwater monitoring systems, better understanding of the role of groundwater storage and groundwater discharges in sustaining aquatic ecosystems, understanding the interactions between various aquifers (including transboundary aquifers) and assessing the impact of increased pumping from various aquifer systems on the sustainability of groundwater abstraction. This paper provides an overview of the regional hydrogeological framework, the current state of knowledge of aquifer systems, their development potential and climate change impacts on groundwater, research gaps, and policy implications for meeting the MDGs of accessing clean water and livelihood goals in Africa

Hydrogeology of an urban weathered basement aquifer in Kampala, Uganda

Weathered basement aquifers are vital sources of drinking water in Africa. In order to better understand their role in the urban water balance, in a weathered basement aquifer in Kampala, Uganda, this study installed a transect of monitoring piezometers, carried out spring flow and high-frequency groundwater level monitoring, slug tests and hydrochemical analyses, including stable isotopes and groundwater residence time indicators. Findings showed a typical weathered basement aquifer with a 20–50-m thickness. Groundwater recharge was 3–50 mm/year, occurring during sustained rainfall. Recharge to a deep groundwater system within the saprock was slow and prolonged, while recharge to the springs on the valley slopes was quick and episodic, responding rapidly to precipitation. Springs discharged shallow groundwater, mixed with wastewater infiltrating from onsite sanitation practices and contributions from the deeper aquifer and were characterised by low flow rates (< 0.001 m3/s), low pH (<5), high nitrate values (61–190 mg/L as NO3), and residence times of <30 years. The deeper groundwater system occurred in the saprolite/saprock, had low transmissivity (< 1 × 10−5 m2/s), lower nitrate values (<20 mg/L as NO3), pH 6–6.5 and longer residence times (40–60 years). Confined groundwater conditions in the valleys were created by the presence of clay-rich alluvium and gave rise to artesian conditions where groundwater had lower nitrate concentrations. The findings provide new insights into weathered basement aquifers in the urban tropics and show that small-scale abstractions are more sustainable in the deeper groundwater system in the valleys, where confined conditions are present

Groundwater flow and storage in weathered crystalline rock acquifer systems of Uganda : evidence from environmental tracers and acquifer responses to hydraulic stress

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Impact of rainfall distribution on the parameterisation of a soil-moisture balance model of groundwater recharge in equatorial Africa

Robust calibration of hydrological models, driven by gridded precipitation data derived from either Regional Climate Models or statistical downscaling of General Circulation Models, is essential to the quantitative analysis of the impacts of climate change on catchment hydrology and freshwater resources. Predicted warming in equatorial Africa, accompanied by greater evaporation and more frequent heavy precipitation events, may have substantial but uncertain impacts on terrestrial hydrology. In this study, we examine how the spatial representation of precipitation influences the parameterisation and calibration of a soil-moisture balance model (SMBM) in the humid tropics of equatorial Uganda. SMBMs explicitly account for changes in soil-moisture and partition effective precipitation into groundwater recharge and runoff. The semi-distributed SMBM, calibrated with daily station data over a 15 year period (1965-1979), estimates a mean annual recharge of 104 mm a-1 and mean annual surface runoff of 144 mm a-1. Interpolation of station precipitation by inverse distance weighting produces a more uniform distribution, and a 7% increase, in mean annual catchment precipitation relative to point-based station data. Application of interpolated (gridded), uncorrected precipitation to the SMBM results in an underestimation of runoff and overestimation of recharge by 57% and 52%; respectively whereas use of corrected, gridded precipitation results in an underestimation of recharge and runoff by 10% and 64%; respectively. Recalibration of the SMBM using gridded precipitation data requires a 3% reduction in potential evapotranspiration, a 12% increase in the runoff-coefficient, and an 18% reduction in the rainfall threshold. These values are inconsistent with local, point-based observations of these parameters. Although current efforts seek to improve the distribution and duration of key hydrological measurements (e.g. soil-moisture, groundwater levels) in data-poor regions, the parameterisation of gridded hydrological models remains largely empirical due to the discrepancy between gridded and locally observed hydrological parameters