Quantifying the impacts of vegetation changes on catchment storage‐discharge dynamics using paired‐catchment data

It is widely recognized that vegetation changes can significantly affect the local water availability. Methods have been developed to predict the effects of vegetation change on water yield or total streamflow. However, it is still a challenge to predict changes in base flow following vegetation change due to limited understanding of catchment storage‐discharge dynamics. In this study, the power law relationship for describing catchment storage‐discharge dynamics is reformulated to quantify the changes in storage‐discharge relationship resulting from vegetation changes using streamflow data from six paired‐catchment experiments, of which two are deforestation catchments and four are afforestation catchments. Streamflow observations from the paired‐catchment experiments clearly demonstrate that vegetation changes have led to significant changes in catchment storage‐discharge relationships, accounting for about 83–128% of the changes in groundwater discharge in the treated catchments. Deforestation has led to increases in groundwater discharge (or base flow) but afforestation has resulted in decreases in groundwater discharge. Further analysis shows that the contribution of changes in groundwater discharge to the total changes in streamflow varies greatly among experimental catchments ranging from 12% to 80% with a mean of 38 ± 22% (μ ± σ). This study proposed a new method to quantify the effects of vegetation changes on groundwater discharge from catchment storage and will improve our predictability about the impacts of vegetation changes on catchment water yields. Key Points Data from paired‐catchment experiments clearly show vegetation changes can alter catchment storage‐discharge relationships Catchment low flow recession equation is reformulated to quantify the changes in groundwater discharge resulting from vegetation changes Changes in groundwater discharge are very important for understanding the impacts of vegetation changes on streamflow at a process level