Abstract
Global food and water insecurity could be serious problems in the upcoming decades with growing demands from the increasing global population and more frequent effect of climatic extremes. As the available water resources are diminishing and facing continuous stress, it is crucial to monitor water demand and water availability to understand the associated water stresses. This study assessed the water stress by applying the water supply stress index (WaSSI) in relation to green (WaSSIG) and blue (WaSSIB) water resources across six major cropland basins including the Mississippi (North America), San Francisco (South America), Nile (Africa), Danube (Europe), Ganges-Brahmaputra (Asia), and Murray-Darling (Australia) for the past 17-years (2003–2019). The WaSSIG and WaSSIB results indicated that the Murray-Darling Basin experienced the most severe (maximum WaSSIG and WaSSIB anomalies) green and blue water stresses and the Mississippi Basin had the least. All basins had both green and blue water stresses for at least 35% (6 out of 17 years) of the study period. The interannual variations in green water stress were driven by both crop water demand and green water supply, whereas the blue water stress variations were primarily driven by blue water supply. The WaSSIG and WaSSIB provided a better understanding of water stress (blue or green) and their drivers (demand or supply driven) across cropland basins. This information can be useful for basin-specific resource mobilization and interventions to ensure food and water security.
Highlights
Water resources are critical for providing human needs of water, energy, and food, and preserving healthy ecosystems (Bhaduri et al, 2016; Vanham, 2016)
WaSSIG was greater than WaSSIB for all basins except the Murray-Darling Basin indicating more water stresses associated with green water compared to blue water
Basin when the precipitation was 24% above average and the least blue water stress (52% below average) was for the MurrayDarling Basin when the precipitation was 35% above average. These results show that WaSSIG and WaSSIB variations followed the trends of basin precipitation; the magnitudes of green and blue water stresses varied across and within basins
Summary
Water resources are critical for providing human needs of water, energy, and food, and preserving healthy ecosystems (Bhaduri et al, 2016; Vanham, 2016). Climate change is deteriorating water resources (Scanlon et al, 2007) and fueling more stress on water resources (Hanjra and Qureshi, 2010; Siegfried et al, 2012), resulting in conflicts during water shortages (Eriksen and Lind, 2009; Theisen et al, 2012; Tang et al, 2018). Water stress assessments at local to regional scale are increasingly crucial to understand the vulnerability and resiliency of water resources. Assessing water stress associated with crop water use (or evapotranspiration) and its relationship with green water (precipitation) or blue water (surface water and groundwater) sources provides integrated information on food and water status.
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