For the Letaba basin situated in the South African part of the Limpopo basin, a hydrological study was carried out in order to quantify the effect of smallholder farming on river flows. Important was to study the consequences of improved agricultural systems on the river flows, in particular for the Kruger National Park situated in the lower part of the Letaba basin. The SIMGRO model was used in this study, which integrates groundwater and surface water. The model was calibrated, and furthermore a comparison of measured discharges and groundwater levels against calculated discharges and groundwater levels, revealed that the model is suiTable for practical analysis. For the smallholders farms different scenarios were defined with different levels of crop yield. An increase in crop yield has consequences on more water use as irrigation and crop water use. Because the area covering smallholder farming is only 0.5% of the basin, the effects of changes in water use are relatively small. In a scenario, the weather conditions for 2050 were analysed. This reveals that discharges will go down by 30% on average, which means a substantial reduction of the water resources.
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