Abstract
Abstract. During the past decades, human water use has more than doubled, yet available freshwater resources are finite. As a result, water scarcity has been prevalent in various regions of the world. Here, we present the first global assessment of past development of water stress considering not only climate variability but also growing water demand, desalinated water use and non-renewable groundwater abstraction over the period 1960–2001 at a spatial resolution of 0.5°. Agricultural water demand is estimated based on past extents of irrigated areas and livestock densities. We approximate past economic development based on GDP, energy and household consumption and electricity production, which are subsequently used together with population numbers to estimate industrial and domestic water demand. Climate variability is expressed by simulated blue water availability defined by freshwater in rivers, lakes, wetlands and reservoirs by means of the global hydrological model PCR-GLOBWB. We thus define blue water stress by comparing blue water availability with corresponding net total blue water demand by means of the commonly used, Water Scarcity Index. The results show a drastic increase in the global population living under water-stressed conditions (i.e. moderate to high water stress) due to growing water demand, primarily for irrigation, which has more than doubled from 1708/818 to 3708/1832 km3 yr−1 (gross/net) over the period 1960–2000. We estimate that 800 million people or 27% of the global population were living under water-stressed conditions for 1960. This number is eventually increased to 2.6 billion or 43% for 2000. Our results indicate that increased water demand is a decisive factor for heightened water stress in various regions such as India and North China, enhancing the intensity of water stress up to 200%, while climate variability is often a main determinant of extreme events. However, our results also suggest that in several emerging and developing economies (e.g. India, Turkey, Romania and Cuba) some of past extreme events were anthropogenically driven due to increased water demand rather than being climate-induced.
Highlights
Freshwater is a vital resource for various human activities and food production
To assess the development of blue water stress over the recent past (1960–2001), we developed a method to reconstruct past water demand and confronted it against the blue water availability simulated by the state-of-the-art global hydrological model PCR-GLOBWB
Similar to Kummu et al (2010), our results show a drastic increase of the global population under moderate to high water stress due to increased water demand during the period 1960–2001
Summary
Freshwater (i.e. blue water) is a vital resource for various human activities and food production. Water needs, primarily for irrigation, have been increasing rapidly since the 1960s. The global water withdrawal increased at a rate of 17 % per decade between 1960 and 2000 (Vorosmarty et al, 2005), and eventually doubled to 4000 km yr−1 in 2000. For North America and Europe, the increase became smaller after the 1980s, whilst water withdrawal consistently increased for Asia, South America, Africa and Oceania for the period 1960–2000. Water scarcity has become prevalent in many regions of the world (e.g. India, China and the Middle East). The United Nations report that water scarcity is beginning to constrain economic growth in those regions (World Water Assessment Programme, 2009)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
