ABSTRACT
ABSTRACT: In many river systems in semi-aridAfrica, water is lost from shallow river-fed aquifers by infiltration and subsequent evapotranspiration. Since groundwater flow is generally directed from the river into the aquifer and evapotranspiration does not entirely remove the dissolved solids with the uptake water, salinity is continuously accumulated in the riverfed aquifer. This paper presents a simple conceptual and numerical model of the river-fed aquifer system. Salt accumulation by evapotranspiration and plant growth inhibition by elevated salinity levels are taken into account. The system reaches a steady state, in which the evapotranspiration is primarily controlled by groundwater quality and only to a minor degree by water availability (depth to groundwater table). A field dataset from the periphery of the Okavango Delta in Botswana (Shashe River Valley) is presented and the developed modelling concepts are applied to this system. Plant-salinity feedback mechanisms are shown to be essential for successful quantitative modeling of Shashe River Valley.
