Unravelling the impact of climate change and anthropogenic activities on streamflow: the benefit of newly developed evapotranspiration data
Vahid Nourani, Ali Gholinia, Peyman Abbaszadeh, Ramin Ahmadi, Chang‐Qing Ke
Abstract
To separate the contributions of climate changes and human activities to alterations in flow for the Ahar Chay watershed in Iran, change points of Normalized Difference Vegetation Index (NDVI) and evapotranspiration (ET) were distinguished before and after significant alterations. The Budyko and Soil and Water Assessment Tool (SWAT) were used to find the reduction in runoff. Newly developed Penman-Monteith-Leuning (PML) ET data was used to consider plant types. Results revealed increase in NDVI, coinciding with the change point in 1998, as well as ET in 1999. The significance of the Sattarkhan Dam within watershed became evident when distinguishing the impacts in upstream and downstream areas of the dam. Results also indicated that climate changes contributed significantly to upstream flow reduction (83.5%), whereas downstream reductions were primarily linked to human-related impacts (59.7-82.5%). Assuming no dam interception, 2007 became the change point, signifying 37.5% reduction in average flow before and after this point due to the increased vegetation cover.