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As the world's population increases, food and water resources will be ever more strained. By 2050, we will need to feed a population of nine billion people, two billion more than today. Climate change, including climate variability, has a direct impact on water availability and irrigation. Notably the loss of ground and surface water, as well as increases in evapotranspiration will place greater stress on the limited availability of fresh water. (Connor J, Schwabe K, King D, Kaczan D, Kirby M (2009) Impacts of climate change on lower Murray irrigation. Australian Journal of Agricultural and Resource Economics 53: 437–456.)Multiple studies have concluded that climate change will have an impact on water availability for agriculture. Notably the loss of ground and surface water, as well as increases in evapotranspiration will place greater stress on the limited availability of fresh water. (Connor J, Schwabe K, King D, Kaczan D, Kirby M (2009) Impacts of climate change on lower Murray irrigation. Australian Journal of Agricultural and Resource Economics 53: 437–456.)
Data on water withdrawals for US states (1985–2005) show that both climate change and resulting water deficits are highly positively correlated with moisture deficit (precipitation - PET). If current trends hold, climate change would increase agricultural demand for irrigation in 2090 by 4.5 -21.9 million ha. Without significant increases in irrigation efficiency, climate change would also increase the average irrigation rate from 7,963 to 8,400–10,415 m3ha.
(McDonald RI, Girvetz EH (2013) Two Challenges for U.S. Irrigation Due to Climate Change: Increasing Irrigated Area in Wet States and Increasing Irrigation Rates in Dry States. PLoS ONE 8(6): e65589. https://doi.org/10.1371/journal.pone.0065589)
(General Problem)
(Farmland not increasing)
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