Modeling the effects of reforestation on peakflow rates of a small watershed in the Three Gorges Reservoir Area

For vegetation construction with hydrological function in the Three Gorges Reservoir Area,the storm event distributed hydrological model PRMS-Storm was built based on MMS(Modeling Module System)developed by the US Geological Survey,and was employed to study the effects of forests on peak flows in the Xiangshuixi Forest Watershed in the Three Gorges Reservoir Area.The results showed that: 1)this simulation study suggested that PRMS-Storm can meet the second level national flood prediction standards for simulating storm events of small forest watersheds,and can issue flood forecasting;2)hydrological functions of different vegetation communities were evaluated,and three simulation scenarios were arranged, they were mixed conifer_broadleaved forests(scenario 1),broadleaved forests(scenario 2) and general forests arrangement(scenario 3);3)the well-arranged forest scenarios can reduce over 20% of surface runoff and result in an increase of over 16% in subsurface flow,and can decrease peak flow by 20.8%,9.6% and 18.9%.The reduction of peak flow rates was significant when rainfall peak was set higher than 0.8 mm/min,especially for short term rainfall events.In general,we found that scenario 1 and scenario 3 were preferable for reducing peak flow rates and volumes in the reforestation practices in the study region,and scenario 1 was better than scenario 3,so the mixed conifer-broadleaved forests had the best hydrological function in theory.However,in practice,considering the natural conditions of watershed,general forests arrangement(scenario 3) should be the best.