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Groundwater provides a vital source of drinking water for rural communities in many parts of Africa, particularly in the dry season when there are few safe alternative sources. This paper summarises results from a study (n = 428) assessing dry season water quality, both microbiological and inorganic chemistry, in handpump equipped boreholes (HPBs) across the Ethiopia Highlands (n = 142), Malawi (n = 162) and Uganda (n = 124) using a stratified, randomised sampling design. This study seeks to examine general water quality by randomly sampling rural groundwater supplies across larger areas with different geology and climate. The majority, 72%, of HPBs surveyed provide good quality dry season drinking water as defined by WHO drinking water quality criteria. Within this overall picture, the most notable constraints were from thermotolerant coliforms (TTCs), which exceeded the WHO drinking water guideline of zero colony forming units (cfu/100 ml) in 21% of sites (range 0-626 cfu/100 ml). TTC contamination was found to have a significant and positive correlation with annual average rainfall (ρ = 0.2, p = 0.00003). Across all three countries, WHO health based chemical drinking water quality values were exceeded at 9% of sites and were found for manganese (4%), fluoride (2.6%) and nitrate (2.5%); arsenic concentrations were below the guideline value of 10 µg l −1 (range < 0.5-7 µg l −1 ). The high percentage of Mn exceedances (14% ± 5.2% >400 µg l −1 ) found in drinking water sources in Uganda challenges the decision by WHO not to formalise a health-based guideline for Mn. While the overall level of microbiological contamination from HPBs is low, results from this study strongly suggest that at a national and regional level, microbiological contamination rather than chemical contamination will provide a greater barrier to achieving targets set for improved drinking water quality under the UN-SDG 6. Efforts should be made to ensure that boreholes are properly sited and constructed effectively to reduce pathogen contamination.

Quantitative analysis of potential field data are made in the Ziway-Shala lakes basin over an area bounded by 38 ° 00′ E - 39 ° 30′ E and 7 ° 00′ N - 8 ° 30’ N. Most previous geophysical studies in the region under consideration focus on mapping the deep crustal structures and undulation of the Moho depth. Only few studies are targeted at mapping the shallow subsurface structures. The main focus of this paper is mapping geometries of the major lithological and structural units of the shallow subsurface using gravity and magnetic data. The ultimate objective of the research is to understand the hydrogeological dynamics of the region through mapping interfaces geometries. Automatic inversions, 2D joint forward modeling and 3D inversion are the major techniques employed. The 2D Werner de-convolution based on both gravity and magnetic data along the rift axis showed source depths tending to deepen northwards. Source depths estimates determined by Source Parameter Imaging also showed similar tendency. This is further strengthened by the joint 2D forward modeling of gravity and magnetic data which showed the top of the basement is sloping northwards. The result of the 3D gravity interface inversion agrees with results of the above mentioned depth estimation techniques. Finally, the gravity power spectral analysis resulted in two depth estimates, 1.53 km and 2.87 km which approximate the positions of two density interfaces. The shallow depth interface is thought to presumably delineate the low density Fluvio-lacustrine sediments including the rift floor volcanic units and crystalline basement. Our investigation results agree with the results of previous seismic studies which identified low velocity (“sediment-volcanic”) horizon in the rift floor with low resolution. The information obtained with regard to water balance of the basin, salinity level of the lakes and the conceptual hydrological flow model appears to reveal that the groundwater flow in the study region is controlled by subsurface structures, particularly, the mapped interface topographies.

The study area, upper Bilate catchment, is strongly dependent on groundwater like other rural catchments in the country. The main objective of this work is to quantify the amount of groundwater recharge in upper Bilate catchment. Recharge was estimated using physically based distributed recharge model called WetSpass. As input to the model precipitation, potential evapotranspiration, temperature and wind speed were estimated using data collected from meteorological stations located within the catchment and nearby areas. The physical environmental data including land use, soil type, and groundwater depth were collected from field and existing maps. Slope and topography map were generated from Shuttle Radar Topographic Mission elevation data. Using the model the mean annual recharge of the catchment was found to be 9.4 % of the precipitation whereas the direct runoff was found to be 20 % of the precipitation. The study area is characterized by lower groundwater recharge relative to surface runoff due to the effect of impermeable soils, morphology of the land and land use/land cover of the study area. The western and northern parts of the area are identified as recharging zone and the central and southern part are discharge zone. The groundwater recharge zoning map was validated using base flow separation method and also compared with previous groundwater recharge works of the study area. This study revealed that the groundwater recharge estimation using WetSpass model is reasonable and useful for quantification of annual groundwater recharge with spatial and seasonal variation and also capable in the identification of groundwater recharge zones in the area under study.

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Background: The use of existing land use/cover type exerts more pressure on the natural dynamism of the watersheds and hydrology due to continued cultivation and mismanagement of land resource. The objectives of this study was to assess the combined effects of land use/cover types and slope gradient on watershed hydrology in terms of sediment and nutrient losses/transport from HRU of each land use/cover types. Integrated soil and water assessment tools (SWAT) model with Arc-GIS was used for simulation of sediment and nutrient loss by using land use/cover, soil, slope and climatic data as input. Analysis of variance (ANOVA) for mean comparison and correlation was used for data analysis. Result: Combined effects of urban land and slope gradient produced more sediment than other land use/cover types followed by cultivated land. In cultivated land as slope gradient increased values of sediment and nutrient losses also increased until it reaches to 30% slope and then declined. In Forest and grassland sediment loss increased until 15% slope then after declined, but in urban land as slope gradient increases sediment and nutrient loss are also increased. Conclusion: Cultivated land and difference in its slope gradient had more significant effect on watershed dynamics and hydrology in terms of loss of fertile top soil from upland, downstream water quality reduction and sedimentation of water structures than others land use/cover types and need to avoid steep slope and continuous cultivation and implementing integrated watershed management strategies in order to keep the natural dynamism of the watersheds.

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