Climate and land-use change affect the hydrologic cycle by altering the hydrological responses including streamflow (SF), surface runoff (SR), base-flow (BF), and evapotranspiration (ET). Several studies have addressed the separate impacts of either land-use or climate change on the watershed hydrology, but few have explored the combined impacts. In this study, the SWAT model was applied to evaluate the combined impacts of land-use and climate change on hydrological responses in Gumara watershed. This study examined four land-use scenarios that include the present and projected land-use based on the business-as-usual trend (BAU), expansion of irrigation crop (EIC), and expansion of forestland (EFL). Climate variables were simulated using Weather Research and Forecasting (WRF) model for the baseline (2005-2015) and projected period (2045-2055) under RCP4.5 and RCP8.5 scenarios. Results showed that SR increase by 5.1% under BAU scenario while BF decrease by 6.5% without altering SF and ET noticeably. On the contrary, SF decrease by 12.5% and 5.2% respectively under EIC and EFL scenarios, while ET increase by 4.8% and 8.9% respectively under EIC and EFL scenarios. The simulated SF, SR, and ET under RCP8.5 may increase significantly by 34.3%, 51.8%, and 12.2%, respectively. Similarly, the simulated SF, SR and ET may increase significantly under the combination of all three land-use and RCP8.5 scenarios. This suggested that climate change will have a greater effect on hydrologic responses than land-use change. The results of this study can be useful to decision-makers and planners in the design of adaptive measures to climate and land-use change.

气候和土地利用的变化通过改变水文响应（包括水流（SF），地表径流（SR），基流（BF）和蒸散量（ET））来影响水文循环。几项研究已探讨了土地利用或气候变化对流域水文学的单独影响，但很少探讨这两种综合影响。在这项研究中，SWAT模型用于评估土地利用和气候变化对古玛拉流域水文响应的综合影响。这项研究检查了四种土地利用情景，包括基于照常经营趋势（BAU）的当前和预计土地利用，灌溉作物的扩张（EIC）和林地的扩张（EFL）。在RCP4.5和RCP8.5情景下，使用天气研究和预报（WRF）模型对基线（2005-2015年）和预计时期（2045-2055年）进行了气候变量模拟。结果表明，在BAU情况下，SR增大了5.1％，而BF减小了6.5％，而SF和ET却没有明显变化。相反，在EIC和EFL方案下，SF分别下降了12.5％和5.2％，而在EIC和EFL方案下，ET分别增长了4.8％和8.9％。在RCP8.5下模拟的SF，SR和ET可能分别显着增加34.3％，51.8％和12.2％。同样，在所有三种土地利用和RCP8.5情景的组合下，模拟的SF，SR和ET可能会显着增加。这表明与土地利用变化相比，气候变化对水文响应的影响更大。