AbstractProjecting surface runoff is a meaningful task for rational allocation and optimal scheduling of water resources. Aimed at exploring the impact of climate change on surface water resources, the basin-scale water-balance model coupled with the Budyko-type equation was developed for the upper Ganjiang River Basin (UGRB). Studies demonstrated that the Budyko-CY function is the optimal water-balance model, with a Nash–Sutcliffe efficiency (NSE) of 0.843 in the calibration period and 0.653 in the validation period, respectively. The increase in temperature by 1 °C may bring about a 2.5–4.7% runoff decline, while the 10% increase in precipitation may lead to a 12.1–14.3% runoff ascent. The annual mean temperature is expected to grow by 0.69, 0.68 and 0.97 °C in the next 30 years relative to that during the reference period, respectively. Similarly, the surface runoff is estimated to increase by 8.4, 6.5 and 5.0% on a multi-year average scale, respectively. This study is beneficial to provide possibilities for climate scenarios that may occur in the future, and the results presented herein are capable of giving a reference for the planning and management of water resources in the UGRB.