An old urban district in Wuhan City,China,is at a transitional stage from discharging sewage and stormwater directly to lakes,to taking the sewage to the wastewater treatment plants(WWTP).How to deal with the polluted stormwater discharges is a great challenge.Stormwater runoff from three urban catchments with combined sewer system was sampled and analyzed through a three-year period.The results indicated that the wet weather flows account for 66,31,17,and 13％ of the total load of suspended solids,COD,total nitrogen and total phosphorus,respectively.The first flush of COD and SS was significant in all runoff events.More than 50％ of the suspended solid and COD loads were transported by the first 30％ of runoff volume.It was found that storage and treatment of the first 10 mm for each combined sewer overflow events could reduce.more than 70％ of the annual COD overflow loads.Three scenarios with tank storage and WWTP treatment,pond storage and wetland treatment,and their combination were suggested.And their costs were estimated for decision makers.These results may be helpful in mitigating stormwater pollution for many other towns of China and other developing countries.