To analyze the water-resource limitations for crops in irrigation districts along the lower reach of the Yellow River, we used the single-crop coefficient method provided by FAO-56 to analyze crop water demand (CWD) and irrigation water requirement (IWR) for the main crops (winter wheat, summer maize, and cotton) from 1971 to 2015. The impact of climate threats on IWR was then quantified based on the standardized precipitation evapotranspiration index (SPEI), following which the conflicts between water demand and water supply were analyzed. The results show that about 75.4% of the total annual IWR volume is concentrated from March to June. Winter wheat is the largest water consumer; it used an average of 67.9% of the total IWR volume. The study area faced severe water scarcity, and severe water deficits occurred mainly between March and June, which is consistent with the occurrence of drought. With the runoff from the Yellow River Basin further decreasing in the future, the water supply is expected to become more limited. IWR is negatively correlated with the SPEI. Based on the relationship between SPEI and IWR, the water allocation for irrigation can be planned at different timescales to meet the CWD of different crops.
Effects of straw application on nitrate leaching in fields in the Yellow River irrigation zone of Ningxia, China
