Conservation of wetlands in drylands: impact of pumping on water availability

In Southern Africa, pumping groundwater to enhance water availability for wildlife living in wetlands during the dry season is a common conservation management practice, particularly in national parks. However, its effectiveness has not been quantitatively assessed despite its implications for woodland dynamics. Modifying wetland hydroperiod may have significant consequences for the conservation of specific communities. Although the ecological consequences of groundwater pumping on megafauna and vegetation are well documented, the magnitude of increased water availability has never been quantified. This knowledge gap is increasingly important given the recent technological shift from diesel to solar pumping, which may further amplify differences in the hydroperiod between natural and pumped wetlands. Using a 37-year Landsat-based dataset of water availability in Hwange National Park, Zimbabwe, we compared the intra- and inter-annual evolution of water availability between pumped and natural wetlands. We found that water availability significantly increased with the implementation of diesel pumping. At the end of the dry season, diesel-pumped wetlands exhibited significantly greater water availability than natural wetlands by compensating for evaporation, infiltration, and animal consumption. When technology switched to solar pumping, this difference widened, with significantly greater and longer water availability throughout the entire dry season. Our study quantified the water availability gap between pumped and natural wetlands on a broad regional scale and over a long timespan. By substantially increasing water availability, the technological shift from diesel to solar pumping may induce significant changes in landscape dynamics and wetland communities in semi-arid regions worldwide.