Effects of climate and land use change on runoff of the second Songhua River Basin guided by SWAT model

The driving effect of global climate change on the ecohydrological process was quantitatively evaluated. Based on Geographic Information System technology, a Soil and Water Assessment Tool model suitable for watershed hydrological simulation was constructed to study the impact of climate and land-use change on runoff in the Second Songhua River (SSR) basin. Within the base period (1965–2010), the annual average temperature (AAT) of the SSR basin is 4.2 °C. Under the CC scenario representing concentration pathway (RCP) 4.5, the AAT of the watershed increased to 5.4 °C between 2020 and 2049. Under the CC scenarios of RCP 8.5 and RCP 4.5, the temperature in the watershed increased by 1.1 and 0.2 °C in June, respectively. The research results indicate that (1) there is a positive correlation between runoff and precipitation in the SSR watershed, and a negative correlation with temperature; (2) when the precipitation remains unchanged, the temperature increases by 1 °C and the runoff decreases by 7.2%; and (3) when the temperature remains constant, for every 10% increase in precipitation, the runoff increases by 30.5%. This study provides the scientific basis for water resource planning and sustainable development in the Northeast region and has important practical significance.