Rainwater shocks and economic growth: The role of the water cycle partition

This paper improves our understanding of how rainwater impacts economic growth by investigating the effects of overlooked properties of the water cycle. First, we consider the natural separation of rainwater into flows of blue water (i.e., the water that runs off towards rivers) and green water (i.e., that remaining in the soil). Second, we account for the presence of surface and groundwater stocks. These considerations allow us to comprehensively address the whole partition of rainwater, which, upon reaching the ground, splits into distinct water resources that determine water availability inland. Our analyses on a global panel coupling sub-national economic and hydrological data show that rainwater does increase growth, but do so differently depending on its partition. Specifically, blue water leads to more economic growth than green water at the margin, but, because two thirds of terrestrial water is green, the latter contributes more to growth in total. By missing this crucial partition, we find that commonly used rainwater measurements overstate rainwater’s contribution to growth (by about two). Our analyses further indicate that, although groundwater reserves always mitigate the impacts of rainwater reduction on growth, surface water reserves sometimes amplify regional dependence to rainwater (depending on sector, income and reserve types).