Water Saving in the Yellow River Basin, China.2. Assessing the Potential for Improving Basin Irrigation

A study focusing the improvement of the basin irrigation is performed in the Huinong Irrigation District (HID), in the upper reaches of the Yellow River basin, Ningxia Province, and in the Bojili Irrigation District (BID), in the lower reaches of the basin, Shandong Province. Studies include the field evaluation of current basin irrigation practices and the use of the simulation models SRFR and SIRMOD to search for improved designs and practices. The target application depths are generated by the irrigation scheduling simulation model ISAREG. For HID, achieving a control of present excess irrigation water applied and the induced water table rise and salinity requires that the basin water advance would be completed in a much shorter time than at present. Therefore, improvements in field sizes, land leveling, infiltration conditions and inflow rates are identified aiming at water savings and controlling waterlogging and salinity. At BID, the main problems relate to excessive field lengths and relatively poor land leveling, which induce very slow advance times, which are associated with excess water application or under-irrigation of the downstream part of the field. Solutions therefore include improved land leveling, larger inflow discharges and reduction of field lengths. The paper summarizes the approaches used to calibrate the simulation models from field observations, an analysis of present conditions and performances, and a discussion on the proposed issues for both areas.