ESTIMATION OF PROBABLE MAXIMUM PRECIPITATION FOR DAMS IN THE HONGRU RIVER CATCHMENT, CHINA

During the summer season, typhoons form in the western north Pacific O cean and travel westward towards China. Some recurve northward off the coast, whereas others continue in over land. These typhoons bring hea vy rainfall to the Huai river basin in eastern central China. In Augus t 1975, the remnant of typhoon Nina caused exceptionally heavy rainfal l in the Hongru river basin, in the mountainous upper reaches of the H uai river. The rainfall lasted five days from 4 to 8 August. This type of nearly stationary typhoon can cause rainfall of large intensity fo r a long duration, and is suitable for maximization to derive probable maximum precipitation (PMP) estimates. The PMP is transformed into a probable maximum flood hydrograph that is subsequently used to design spillways etc. In this study the PMP values have been estimated using a hydrometeorological method involving depth-area-duration analysis, m oisture maximization, and altitude adjustment for typhoon Nina, for 1, 2, and 3 days duration. Areal PMP values were obtained for the entire Hongru river catchment, as well as for the subcatchments upstream the dams at Banqiao (762 km(2)), Shimantan (230 km(2)), Boshan (580 km(2) ), and Suyahu (4498 km(2)). For point values, the PMP was estimated to 1200 mm/day, 1460 mm/2 days, and 1910 mm/3 days at altitudes about 10 0 m, which agrees well with previous studies.