Modeling Impact of Climate Change on Nutrient Loadings in Fei-tsui Reservoir Watershed

Dynamic modeling and an Early Warning Index (EWI) were used to quantify the impact of projected climate change on streamflow and nutrients export from Fei-tsui reservoir watershed in northern Taiwan. The Taiwan Water Resources Assessment Program to Climate Change (TaiWAP) and the Generalized Watershed Loading Functions (GWLF) models were chosen as dynamic modeling tool. To explore the impacts under different climate change conditions, three scenarios (A2, A1B and B1) of IPCC Special Report on Emissions Scenarios (SRES) with two General Circulation Models were employed to drive the climate simulations.

The results showed that, the streamflow will significantly decreases in dry season under climate change in Fei-tsui reservoir watershed. This trend indicates that climate change has more impact on changing the seasonal distributions than on altering average annual amount of the streamflow and nutrient loading. Based on the results, EWI of total phosphorus loading is greatly higher than EWI of total nitrogen loading. The results indicated that total phosphorus loading under A2 scenario in dry season in the period of year 2079~2099 will be the worst scenario for water quality in Fei-tsui Reservoir watershed. The mitigation management strategy is to change the land use type and area of Fei-tsui Reservoir watershed, suggestion would be to transfer the agriculture area to forest, the results indicated that it is an effective strategy, EWI reduced after the applying the strategy.