GRAIN: Mapping the World's Irrigation Canals and Why It Matters for Water, Food, and Climate

Abstract The engineered channels that carry water from large dams and rivers to agricultural fields, known as irrigation canals, are the link between source (lakes and reservoirs) and sink (farmlands). These canals make cultivation of crops possible across millions of hectares of land. A comprehensive global map of irrigation canals has, until now, been missing. We introduce in this perspectives, a comprehensively prepared and curated geospatial data set called Global Registry of Agricultural Irrigation Network (GRAIN). With GRAIN, which documents nearly 3.8 million km of canal geometry, we believe it will become easier to understand how surface water is being distributed for crop production, or how heavily groundwater is being relied upon to compensate for surface‐water shortages. Lastly, the GRAIN data set will hopefully open the door to fully leverage the expanding wealth of satellite data now available to monitor agricultural water use.