Agricultural water productivity can be defined as the ratio of crop yield to “evapotranspiration,” which means the amount of water needed to grow a crop. Improving water productivity is an important approach to achieving global food security amidst increasing water scarcity. Increasing water productivity in the Yellow River Basin (YRB) is especially critical as it is a key global food-production center facing a rapidly decreasing water supply. The basin contains 13 percent of the total cultivated area in China but it holds only 3 percent of the country’s water resources. Basin water resources depend chiefly on a continental monsoon climate with relatively low precipitation con-centrated in a few months of the year. As a result, rainfall does not often meet the water demand of crops throughout the duration of the growing period; thus, much of the area relies on irrigation for basic staple crops. Given the size of the basin, however, there is significant variation across water supply and demand. Examining these varying water productivity levels provides important insights for policy analysis.
This project note is based on data from 60 counties in the upstream, midstream, and downstream areas of the YRB used to assess water productivity for both key irrigated (WPI) and rainfed (WPR) crops in the basin; results were extrapolated for the entire basin using crop area as the weighting factor. Sources include experi-mental data, statistical data, and empirically estimated data in order to analyze major crops (corn, wheat, rice, and soybean) in the 461 counties constituting the basin. County-level data reveals that all rice and wheat are irrigated across the YRB. Wheat grows during the winter–spring season, when precipitation is very limited (less than 30 percent of crop water demand). About 11 percent of maize and 17 percent of soybean area are rainfed. However, a large share of irrigated crops in the YRB belongs to the category of supplementary irrigation due to the synchronized pattern of precipitation and solar energy in the basin.