Thesis Abstract Andersen
The demand for clean freshwater is continuously increasing globally as population and development grow over time. This is particular problematic in semi-arid and arid region, as these are especially vulnerable to water scarcity of surface water. The importance of groundwater as a source of freshwater is accordingly expanding in these region and it is unknown if this resource can sustain further exploitation (MacDonald et al. 2012).
The need for hydrological model, capable of predicting the water balance on a catchment scale is imperative, if sustainability is to be maintained. This thesis will therefore present a fully integrated hydrological model of the Hout/Sand catchment of the Limpopo region in South Africa. The results show a recharge of 11.7 of MAP across the catchment which is in line with findings of Bredenkamp et al. (1995), but significantly higher than findings by Girma Y. Ebrahim et al. (2019) and Holland (2011). Previous studies of the region (Holland 2012; Holland and Witthüser 2011; Girma Y Ebrahim et al. n.d.; Girma Y. Ebrahim et al. 2019) have found that the productivity of wells near dykes is larger than for other well. The results of or model suggest that this may be a result of the dykes obstructing the groundwater flow, causing an local increase in hydraulic head on the front-side(facing flow) of the dykes.
The study furthermore finds the current irrigation is causing a local decrease in hydraulic head, where irrigation is concentrated. We found that as much as 73% of the groundwater use for irrigation is lost to evapotranspiration instead of recharging. The study also found that the immediate effect on the water table in response to focused recharge from rivers, does not extent past 1200 m from the source, and is delayed and attenuated within the first 400 m.