Interactive impacts of climatic, hydrologic and anthropogenic activities on watershed health

The current study aimed to comprehensively assess the potential watershed health (WH) using an adapted reliability, resilience and vulnerability (R_elR_esV_ul) framework for the 24 sub-watersheds of Shazand, Markazi Province, Iran. Towards this goal, the appropriate criteria and acceptable corresponding thresholds were adapted to calculate the main WH indictors of reliability (R_el), resilience (R_es) and vulnerability (V_ul). Accordingly, the R_elR_esV_ul framework was conceptualized and customized for five criteria of standardized precipitation index (SPI), normalized difference vegetation index (NDVI), soil erosion, and low and high flow discharges. The effect sizes of used criteria and indicators on the Shazand WH status were also determined. Consequently, the status of R_el, R_es and V_ul indicators and integrated WH status were mapped for four years of 1986, 1998, 2008 and 2014 and for the whole watershed by developing an integrated watershed health index (IWHI). Finally, the change detection approach was applied to determine the trend of changes in IWHI during last three decades. The results approved the high variability in effectability of R_el, R_es and V_ul indicators and integrated health status of the Shazand Watershed from the selected criteria in study four years. The results revealed that in the all study years, the R_el indicator almost had the higher contribution rate (≥34%) in the Shazand WH. None of sub-watersheds in the study years were assessed in a healthy status in terms of IWHI based on the R_elR_esV_ul framework. In terms of WH change detection over the study periods, WH was found to declining by some 4% in the periods of 1986-1998 and 1986-2008 due to impact of industrialization and urban development. Whilst, the health status was non-significantly improved in other study periods. The present procedure can be supposed as a screening tool for a directive and efficient management of the watersheds.