An article published in Earth's Future reported that by 2050, agricultural water scarcity will intensify in more than 80% of global croplands.

The study uses an agricultural water scarcity index to estimate agricultural water scarcity under climate change in the future. The index incorporates blue water, which comes to farmland from rivers, lakes, and underground sources through irrigation, as well as green water, which comes directly to farmland through rainfall and is stored in the soil. It provides an integrated representation of agricultural water scarcity for both irrigated and rainfed farmland.

Estimates suggest that under climate change, the degree of agricultural water scarcity would increase in more than 80% of cropland. The intensified water scarcity would be dominated by the decreasing water availability and by increasing crop water requirements associated with climate change. The study also showed that green water has a significant contribution to future changes in water scarcity in 16% of global croplands.

The results of this study would enhance our understanding of water scarcity and the necessity of improving the utilization of green water in croplands that may alleviate water scarcity in future global warming.

One measure to increase green water availability is the installation of small reservoirs. Small reservoirs are expected to have the potential to increase green water more than conventional large-scale irrigation systems based on blue water because small reservoirs store surface water and use water near the source.

JIRCAS has been conducting research in Asia and Africa focusing on the installation, management, and water use of reservoirs, and has compiled the results in papers and manuals.

Supplementary Irrigation Manual for Rice Production Using Small Reservoirs

Pond water use planning tool for integrated farming

JIRCAS Openhouse Mini-lecture: Earth’s Water is All Connected

References
Xingcai Liu et al, Global Agricultural Water Scarcity Assessment Incorporating Blue and Green Water Availability Under Future Climate Change, Earth's Future (2022). DOI: 10.1029/2021EF002567

Wisser, Frolking et al. The significance of local water resources captured in small reservoirs for crop production – A global-scale analysis. Journal of Hydrology (2010). DOI:10.1016/j.jhydrol.2009.07.032

Contributor: OKA Naoko (Rural Development Division)