In the inner Aral Sea Basin of Central Asia, numerous small lakes scattered over the irrigated landscape supply diverse ecosystem services for humans and nature. This study aimed to estimate the water volumes and assess the potentials of these small lakes for instance as irrigation reserve during the ever-recurring periods of water scarcity in the ecologically endangered Amudarya Delta. Bathymetric measurements gathered in the Khorezm region, Northwest Uzbekistan, permitted developing a statistical relationship between the surface and volume of the lakes. Landsat satellite data enabled for classifying the water bodies and hence deriving lake volumes over the study area. In 2002, the lakes stored ~0.032 km³ water during the winter season, but ~0.057 km³ during the main, 5–6 months spanning irrigation period. The area-wide increase in lake volumes during the irrigation period underlined the magnitude to which the currently practiced, inefficient use of irrigation water, produces excess water that in turn contributes to the existence of the small, mesotrophic lakes. Based on crop water requirements, calculations showed that the reuse of lake water may compensate for water-scarce situations, albeit to a certain extend only. An increased share (13 % above average) of water-intensive rice fields in the vicinity of the lakes substantiated that some lakes are already used in this way. It is argued that, in case of sufficient water quality, as indicated by other studies, more targeted exploration of such lake water can help simultaneously both, increasing food and water security of the households surrounding the lakes and safeguarding a supply to maintain different ecosystem functions. Integrated management of all water resources may reduce excess irrigation water supply to the region, which in turn may lessen the dependency of Central Asian downstream countries on transboundary water and supply water resources for the ecosystems in the river deltas.

Land Use Land Cover Change (LULCC) has a significant impact on water resources and ecosystems in sub-Saharan Africa (SSA). On the basis of three research projects we aim to describe and discuss the potential, uncertainties, synergies and science-policy interfaces of satellite-based integrated research for the Kilombero catchment, comprising one of the major agricultural utilized floodplains in Tanzania. LULCC was quantified at the floodplain and catchment scale analyzing Landsat 5 and Sentinel 2 satellite imagery applying different adapted classification methodologies. LULC maps at the catchment scale serve as spatial input for the distributed, process-based ecohydrological model SWAT (Soil Water Assessment Tool) simulating the changes in the spatial and temporal water balance in runoff components caused by LULCC. The results reveal that over the past 26 years LULCC has significantly altered the floodplain and already shows an impact on the ecosystem by degrading the existing wildlife corridors. On the catchment scale the anomalies of the water balance are still marginal, but with the expected structural changes of the catchment there is an urgent need to increase the public awareness and knowledge of decision makers regarding the effect of the relationship between LULCC, water resources and environmental degradation.

The feasibility of a hydrogeological modeling approach to simulate several thousand shallow groundwater-fed lakes and wetlands without explicitly considering their connection with groundwater is investigated at the regional scale (~40,000 km²) through an application in the semi-arid Nebraska Sand Hills (NSH), USA. Hydraulic heads are compared to local land-surface elevations from a digital elevation model (DEM) within a geographic information system to assess locations of lakes and wetlands. The water bodies are inferred where hydraulic heads exceed, or are above a certain depth below, the land surface. Numbers of lakes and/or wetlands are determined via image cluster analysis applied to the same 30-m grid as the DEM after interpolating both simulated and estimated heads. The regional water-table map was used for groundwater model calibration, considering MODIS-based net groundwater recharge data. Resulting values of simulated total baseflow to interior streams are within 1% of observed values. Locations, areas, and numbers of simulated lakes and wetlands are compared with Landsat 2005 survey data and with areas of lakes from a 1979–1980 Landsat survey and the National Hydrography Dataset. This simplified process-based modeling approach avoids the need for field-based morphology or water-budget data from individual lakes or wetlands, or determination of lake-groundwater exchanges, yet it reproduces observed lake-wetland characteristics at regional groundwater management scales. A better understanding of the NSH hydrogeology is attained, and the approach shows promise for use in simulations of groundwater-fed lake and wetland characteristics in other large groundwater systems.