The study on estimation of groundwater recharge was done in Grasslands Catchment, about 70 km south-east of Harare, Zimbabwe. The catchment is underlain by Archean Granitic rocks intruded by dolerite dykes/sheets and form part of the Basement Complex. The catchment is a stream headwater wetland, at the source of Manyame River. The catchment comprises an upland region or interfluves of area 2.12 km2 and a dambo area of 1.21 km2. The study focused on the assessment of temporal and spatial variability of moisture fluxes based on solute profiling, and groundwater recharge and investigations of moisture transport mechanisms. The methodology involved the use of both hydrometric and hydrochemical techniques. Groundwater recharge rates and moisture fluxes were calculated using a chloride mass balance technique in comparison to the hydrograph separation technique. Groundwater recharge was estimated to be 185 mm/year using the chloride mass balance and 215 mm/year using the hydrograph separation technique. Mechanisms of recharge were investigated using the bimodal flow model that comprised of diffuse flow and preferential flow. The results revealed that preferential flow contributes up to 95% of the recharge in the interfluves, whilst diffuse flow contributes up to 5% of the total recharge. The results reveal that the groundwater hydrograph technique results are in agreement with the chloride mass balance method. The study illustrated how routine observations can improve process understanding on groundwater recharge mechanisms. The techniques are not expensive, are easy to use and can be replicated elsewhere depending on availability of data.
Presenter Name
Muchanyara
Presenter Surname
Jarawaza
Area
Grasslands Catchment, Marondera, Zimbabwe
Conference year
2013
Keywords