| Abstract: | Climate and land use/cover (LUC) are the two most significant factors that directly affect
the runoff process. However, most research on runoff response has focused mainly on projected
climate variation, while future LUC variability has been neglected. Therefore, the objective of this
study is to examine the impacts of projected climate and LUC changes on runoff. Future climate
scenarios are projected using the Quantile Mapping (QM) method, and future LUC scenarios are
predicted with the Cellular Automaton-Markov (CA-Markov) model. Three different scenarios are
simulated and compared to evaluate their impacts: Scenario 1 (LUC of 2010 and climate during the
2011–2050 period, abbreviated S1), Scenario 2 (LUC of 2010, 2020, 2030, 2040 and 2050 and climate
of the historical wet year, normal year and dry year, abbreviated S2) and Scenario 3 (LUC of 2010,
2020, 2030, 2040 and 2050 and corresponding climate projections of 2011–2020, 2021–2030, 2031–2040
and 2041–2050 period, abbreviated S3). These three scenarios are then input into the Soil and Water
Assessment Tool (SWAT) model to assess runoff responses. Beijiang River Basin, located in southern
China, is used in this case study. The results obtained from S1, S2 and S3 show that runoff change
in this basin is mainly caused by climate change; warmer temperatures and greater precipitation
increase runoff. LUC change has little influence on runoff at the whole-basin scale, but changes in
runoff components are more notable in the urban area than in the natural region at the sub-watershed
level. The impact of LUC change in urbanized region on runoff components differ obviously among
the wet, normal and dry years, and surface runoff and groundwater are found to be more sensitive to
urbanization. Runoff depth is predicted to increase in this basin under the impacts of both climate
and LUC changes in the future. Climate change brings greater increase in water yield and surface
runoff, whereas LUC change leads to changes in allocation between surface runoff and groundwater
in the urban region. |