Regional-scale partitioning of transmission losses and groundwater recharge using satellite estimates of actual evapotranspiration in an arid environment

Abstract

Rivers in arid regions often rely on flow generated from wetter regions upstream, leading to high transmission losses of downstream flows. These transmission losses support a range of ecosystems, but partitioning the volume of the transmission losses across the floodplain, riparian zone and in-channel is difficult. This study presents a methodology relying primarily on multi-decade satellite remotely sensed actual evapotranspiration estimates to partition these losses. The method was applied to the ~40,000 km2 floodplain of Cooper Creek in the central Australian arid zone, where first, the alluvial landscape was classified based on actual evapotranspiration rates, and second, both regional- (i.e., for the entire floodplain) and local-scale (i.e., for each waterhole) water balances were calculated to partition these losses. Regional-scale results estimated that 82% of transmission losses occurred on the floodplain, 13% in the riparian zone and 5% from open water in the river channel and waterholes. These results showed that a refinement of the conceptual model of recharge from the waterholes is necessary as vast areas of the riparian zone are likely to be accessing a shallow freshwater lens rather than a discrete freshwater lens below the permanent waterholes. This method can be used in other data-poor arid river systems as it uses globally accessible data sources.