Estimation of irrigation requirement for sustainable water resources reallocation in North China

The South-North Water Transfer (SNWT) project (upon completion) will deliver some 4.8 billion m³ of water per annum to Hebei, Beijing and Tianjin — greatly mitigating water shortage in North China. Surface water that is currently restricted to urban use could then become partly available for agricultural production. This will reduce the dependence of agriculture on groundwater, which will in turn retard groundwater depletion in the region. This study determines the spatial and temporal distributions of agricultural water requirement in Hebei Plain. This in turn lays the basis for surface water reallocation following the completion of the SNWT project. DSSAT and COTTON2K crop models are used along with crop coefficient methods to estimate required irrigation amounts for wheat, maize, cotton, vegetables and fruit trees in Hebei Plain. The study uses 20 years (1986-2006) of agronomic, hydrologic and climate data collected from 43 well-distributed stations across the plain. Based on the results, wheat accounts for over 40% of total irrigation water requirement in the plain. Similarly, wheat, maize and cotton together account for 64% of the total irrigation water requirement. The piedmont regions of Mount Taihang have the highest irrigation requirement due to high percent farm and irrigated land area. The months of April and May have the highest irrigation water requirement, respectively accounting for 18.1% and 25.4% of average annual irrigation. Spatial and temporal variations in our estimated irrigation water requirement are higher than those in the officially published statistics data. The higher variations in our results are more reflective of field conditions (e.g. precipitation, cropping pattern, irrigated land area, etc.). This therefore indicates a substantive improvement (in our study) over the average statistical data. Based on our simulation results, viable surface water reallocation strategies following the completion of the SNWT project are advanced and discussed.