Development and application of a new index-overlay method to assess urban runoff vulnerability to contamination (evaluation in the Ardabil city, Iran

Abstract

Urban runoff is an effective alternative water resource, particularly in arid and semi-arid regions. Urban runoff exploitation permits cities to have a significant amount of water, but without assessing the runoff quality, harvesting of this resource is complicated and requires further investigations. Due to the lack of a specific method, in this study, a new index method (WLTR) was developed for assessing the urban runoff vulnerability to contamination. The WLTR index is based on rating different subfactors of wastewater (W), land use (L), transportation (T), and rainfall runoff (R) factors. The efficiency of the WLTR index was investigated in 12 sub-catchments of the Ardabil city in Iran. The priority of sub-catchment vulnerability was determined via WLTR index value. The efficiency of the developed method was investigated using direct measurement of several water quality parameters (pH, EC, TDS, TSS, TH, and SO4) in the sub-catchments outlet. A Water Quality Index (WQI) was calculated for each sub-catchment. The quality priority of sub-catchments was determined based on the WQI value. According to the measured data, an acceptable efficiency was observed for WLTR index. According to the results, the most vulnerable sub-catchments (Nos. 4, 11, and 12) had the lower runoff quality among studied sub-catchments, whereas the least vulnerable sub-catchments (Nos. 2, 9, and 8) had the higher runoff quality