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Re-envisioning the hydro cycle
Published in Liz Roberts, Katherine Phillips, Water, Creativity and Meaning, 2018
Rebecca L. Farnum, Ruth Macdougall, Charlie Thompson
Perhaps most obviously missing from the classic hydro cycle are humans: The vast majority of diagrams do not include a single individual or societal influence, appearing as animal- and human-free landscapes. This remains the case even though humans use, disrupt, redirect, and recycle water flows in a multitude of ways. Concepts like the ‘precipitationshed’, which refers to the upwind land and ocean from which rain in one area evaporated, recognise that actions in one area impact water availability, quality, and flows in other areas. Local actions have global impacts – global trends affect local issues – even as we continue to ‘lack an adequate understanding of how the overall system works’ (Vörösmarty et al. 2004, 513). In the introduction to the ‘Geographies of Water’, Fonstand (2013) points out that many of these human-induced changes are not new, but neither are they fully known. It is clear we need to better understand and respond to the connections between humanity, hydrologic flows, and ecosystems.
Water resilience and human life support - global outlook for the next half century
Published in International Journal of Water Resources Development, 2020
The concept of the precipitationshed indicates how upwind terrestrial evaporation source areas contribute moisture for precipitation to downwind sink regions. Keys (2016) identified seven terrestrial, water-constrained, recycling-dependent sink regions with 500–600 mm rainfall and vulnerable to upwind land use change. Many of these areas are also priority areas for global development. Two of Keys’s seven cases have particular interest because of size and population: the Sahel and north and east China. In the western Sahel there is high local recycling and no absolute contribution from the nearby Sahara at present, but greater future evaporation in the Sahara might have large effect on precipitation in the Sahel. The precipitationshed is vast, containing 83 countries and more than 900 million people. The Chinese sink regions have the highest vulnerability of the seven regions, due to many potentially evaporation-altering land cover changes: expanded urbanization as well as irrigated cropland, deforestation in both East and South-East Asia and afforestation in northern China. They also have the largest populations, with eastern China exceeding 2 billion.