Influence of land-use changes and climate change on streamflow simulations: A case study of the Jiao-long watershed

The Markov model and the special report on emissions scenarios (SRES) climate scenario were applied to investigate the influence of future land-use changes and climate changes on the streamflow simulation of the generalized watershed loading function (GWLF) model, and also to assess the impacts on the Jiao-Long watershed, of central Taiwan. Land-use maps in 1971 and 1998 were first digitized. The Markov model was then constructed according to those land-use data and applied to predict future land-use changes. Results of the Markov prediction indicated that the area of unlawful cultivation would increase from 0.36% in 1971 and 2.40% in 1998 to 3.29% in 2025, 6.13% in 2052, and 8.87% in 2079. In addition, the climate change data retrieved from the SRES were finally integrated with the Markov predictions in order to analyze the influence of future land-use changes and climate changes on the streamflow simulation of the GWLF model, and also to assess the impacts on the watershed. Results showed that, regardless of whether considering the short-, middle- or long-term simulation, values of monthly average streamflow, annual total streamflow, and annual average streamflow all changed. Furthermore, land-use changes and climate changes would lead to increases in the occurrences of storms and floods in the wet season, and drought in the dry season.