Increasing Streamflow in Poor Vegetated Mountain Basins Induced by Greening of Underlying Surface

Arid ecosystems have exhibited greening trends in recent decades. There is no consensus on how underlying surface changes influence streamflow across vegetation gradients. We investigated this issue for the four typical arid mountain basins using a 30-year runoff database and the Budyko framework to quantify the contributions of climate and underlying surface changes to streamflow variations during summer periods. Results showed that in the poor vegetated basins, i.e., Heizi Basin and Kuche Basin, the underlying surface change has increased summer streamflow by 14.01 and 35.67 mm, respectively; climate contributed only −7.32 and 1.86 mm to summer stream-flow changes, respectively. Comparatively, in the well-vegetated basins, i.e., Huangshui Basin and Kaidu Basin, climate change dominated summer streamflow variations by increasing 21.50 and 24.65 mm, respectively; the underlying surface change only increased summer streamflow by 3.72 and 1.56 mm, respectively. Additionally, the decomposition results were extended to monthly scale (from June to September) to reveal the effects of climate and underlying surface changes on monthly streamflow. This study deepens our knowledge of runoff responses, which can provide important references to support water resources management in other regions that receive water from mountains.