Melting of ice in the Himalayas. The precipitation and melting pattern of snow impacts on irrigation in the lowlands is changing.
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Change in snowmelt threatens water supply for irrigation

In mountain regions, snow accumulates in the winters and melts in spring. Due to global warming, timing and the amount of melting water changes, which may have profound effects on irrigation in river basins and on water supply world-wide.

Snow, which accumulates in numerous mountainous regions in winter and melts in spring and summer, makes a significant contribution to the supply of irrigation water in many river basins. The observed change in the climate is affecting the amount and timing of snowmelt. In a global study, an interdisciplinary research team led by Ohio State University, USA, and including agricultural scientists from the University of Göttingen in Germany, have investigated how a warming of 2° or 4° Centigrade would affect the supply of water from snowmelt to irrigation areas. The results were published in the journal Nature Climate Change in April 2020.

It has been shown that water from snowmelt makes an important contribution to the supply of irrigation water in many irrigation areas in Central Asia, the Himalayas, the western USA and the southern Andes. In the period 1985-2015, more than 50 per cent of the global irrigation water requirement for barley was met by snowmelt in the months of March to May, and this was also the case for cotton in the months of May and June. 

With global warming, the share of irrigation water supply from snowmelt decreases in almost all snowmelt-dependent areas, e.g. from 33 per cent to 18 per cent in the San Joaquin Basin in California, USA, or even from 29 per cent to 9 per cent in the Po Basin in northern Italy. Other areas strongly affected by such changes are the Rhône Valley basin in Switzerland and France, the Ebro basin in Spain and the Amu Darya basin in Central Asia.

Irrigation demand must be met by new alternative water supplies 

"The considerable reduction in water availability from snowmelt during the period when irrigation should occur does not necessarily mean that we will inevitably be affected by water shortages and crop failure if the temperature rises by 4°Centigrade," says Professor Stefan Siebert from the University of Göttingen, Department of Crop Sciences, who was involved in the study. "Rather, we show that adaptations through alternative water supply options such as groundwater use, construction of reservoirs or inter-basin water transfers will be necessary.” 

The study thus makes an important contribution to identifying where such adaptation measures are particularly needed to limit the impact of reduced snowmelt on the supply of irrigation water.”

Siebert made a significant contribution to the study by calculating the monthly irrigation water requirements of the different crop species. The other co-authors conducted research at Ohio State University, University of California Irvine, the University of California Merced, the University of Idaho, Dartmouth College, Lamont-Doherty Earth Observatory of Columbia University Palisades and Colorado State University, all in the USA. 

(University of Göttingen/wi)

Original Publication: Yue Qin et al.: Agricultural risks from changing snowmelt. Nature Climate Change, DOI 10.1038/s41558-020-0746-8

More information on water:
Rural 21, Issue 1/2020: Water for food and agriculture

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