Protecting the lake-reservoir water environment plays an important role in the water use for production and lives,maintenance of ecological equilibrium,development of tourism industry.Water quality target management is an effective way to protect the lake-reservoir water.This paper took Shahe Reservoir and its catchment within the Tianmuhu Reservoir area as the study area.By developing a catchment-scale hydrological and water quality model,hydrological flux and water quality in the Shahe Reservoir catchment were simulated,and N and P fluxes into the Tianmuhu Reservoir and their main sources were evaluated.Based on water quality target of the Tianmuhu Reservoir,environmental capacity for N and P pollutions and the amounts required for reduction were calculated.Integrating with the ecological protection goal and suitability assessment of land for development,strategies on zoning reduction of N and P pollutions and land regulation have been explored.The results show that the amounts of N and P flowing into the Shahe Reservoir are 206.01and 3.29 t/a,respectively,with 85.7% and 67.5% from diffuse sources.The difference in output intensity of N and P is significant between various land use types.Land use with the largest output intensity of total nitrogen is tea garden,and then followed in turn by farmland,built-up land,bare land,grassland,abandoned farmland,forests,and wetland.Output intensity of TP is closely related with the land surface coverage,from which bare land is the largest.The rest are built-up land,tea garden,farmland,grassland,abandoned farmland,forests and wetland in turn.From the perspective of N and P transportation processes,the output of TN from the whole catchment is 321.64 t/a,and input amount into the rivers is 255.53 t/a,with 19.4% loss in river channels.Ultimately 206.01 t/a of TN flowed into the Shahe Reservoir.As for TP,the total amount from the catchment is 13.42 t/a.There is 7.90 t/a entering into the rivers,with approximately 58.3% loss in the river channel, and finally 3.29 t/a flowing into the reservoir.The river retention rates of N and P vary between zones,with 34.71% for total nitrogen and 84.31% for total phosphorus,respectively.Based on the results of 2009 on calculated fluxes,the input TN should reduce 32.01 t/a (or decrease 15.50%) and 59.66 t/a (or decrease 29.00%) to meet the criterion of IV and III water quality, respectively.For TP,the input should reduce 0.682 t/a (or decrease 20.70%) and 1.479 t/a (or decrease 44.90%) to meet the criterion of type III and II water quality,respectively.To reduce the diffuse pollution via regulating land use,indexes such as plant coverage,water resource preservation,land slope,land use,N/P contribution from each zone and the distance from the road and villages,should be used to assess the ecological preservation value and exploit applicability,which can help to define the exploit levels,that is forbidden area,restricted area and preserved area.