Majority of 21st century global irrigation expansion has been in water stressed regions

Abstract

The expansion of irrigated agriculture has increased global crop production but resulted in widespread stress to freshwater resources. Ensuring that increases in irrigated production only occur in places where water is relatively abundant is a key objective of sustainable agriculture, and knowledge of how irrigated land has evolved is important for measuring progress towards water sustainability. Yet a spatially detailed understanding of the evolution of global area equipped for irrigation (AEI) is missing. Here we utilize the latest sub-national irrigation statistics (covering 17298 administrative units) from various official sources to develop a gridded (5 arc-min resolution) global product of AEI for the years 2000, 2005, 2010, and 2015. We find that AEI increased by 11% from 2000 (297 Mha) to 2015 (330 Mha) with locations of both substantial expansion such as northwest India and northeast China and decline, such as Russia. Combining these outputs with information on green (i.e., rainfall) and blue (i.e., surface and ground) water stress, we also examine to what extent irrigation has expanded unsustainably in places already experiencing water stress. We find that more than half (52%) of irrigation expansion has taken place in areas that were already water stressed in year 2000, with India alone accounting for 36% of global unsustainable expansion. These findings provide new insights into the evolving patterns of global irrigation with important implications for global water sustainability and food security.

Solutions to agricultural green water scarcity under climate change

“…The map shows the distribution of rain-fed croplands facing agricultural GWS under baseline (1996–2005 period), 1.5°C warmer, and 3°C warmer climatic conditions. “Currently irrigated croplands” represent the most up-to-date extent of global irrigated lands in 2015 ( 42 ).…”

“…1 ). Because croplands in India and China are mainly irrigated and have few rain-fed cropping systems, these countries will show little increase in GWS under warming ( 38 , 42 , 43 ) (Fig. 1 ).…”

“…In our assessment, we use growing stages for year 2000, as provided by the MIRCA2000 data set. We focus on GWS assessment over a rain-fed cropping system using the latest avaiable irrigation data updated to year 2015 ( 42 ). Here, we define irrigated croplands as croplands with an area > 5% equipped for irrigation ( 42 ).…”

“…We focus on GWS assessment over a rain-fed cropping system using the latest avaiable irrigation data updated to year 2015 ( 42 ). Here, we define irrigated croplands as croplands with an area > 5% equipped for irrigation ( 42 ). We assess monthly GWS by averaging the results of 18 climate and hydrological model combinations under 1.5°C and 3°C warming scenarios.…”

Why the 2022 Po River drought is the worst in the past two centuries

“…To test the significance of this additional driver, we extract and analyze gridded data for the Po River basin from a global dataset of sectoral water use from 1970 to 2010 (39,40), which reveals negative, but nonsignificant, trends for irrigation water withdrawals during summer (table S4). However, such dataset may not consider local features in detail, and, therefore, we analyze the progress in the Po basin of the area equipped for irrigation (37,41,42), which has sizably increased over time, from 0.86 million ha in 1900 to 1.38 million ha in 1960, up to 1.63 million ha in 2015 (fig. S9).…”