Vulnerability assessment and production of the risk map of the contamination is considered as a managerial significant technique in the conservation of Karstic water resources. Karst aquifers in semi-arid regions of the West of Iran with respect to the region’s natural conditions are prone to contamination. The present paper aims to estimate the value of vulnerability and to produce the map of the Karst aquifer of Gilan-e-Gharb in the West of Iran against the pollution diffusion, using COP model. The model estimates the vulnerability of the Karst's water resources against the contamination using three parameters: overlying layer (O), density of current (C), precipitation regime (P). The results show that 0.25% of the region's area is located in a very low vulnerability domain, and 25.5% of the region's area is in a low vulnerability domain, which represents a low vulnerability of this Karst aquifer against pollution. Most regions with a low and moderate vulnerability - in the dominion of developed Karsts of the Asmari limestone formation - are located in the high lands. The dominant vegetation of the region is mostly covered by forest and dense pastures, and its total amount of precipitation is more than 600mm. In general, C, P and O parameters play the most significant role in reducing the value of the vulnerability over the area of study, respectively. The C factor plays the most important role in lessening the vulnerability of the region due to the little area of developed Karsts, high district of non-Karst regions, and lack of suitable vegetation. On the other hand, the region’s precipitation is relatively low which results in a decrease in the amount of contamination permeation. The map of (O) factor shows a high and very high vulnerability of the region, which represents the expansion of permeable structures in the region. The high vulnerability value of this factor is adjusted by other two factors, and on the whole, the vulnerability amount of region is kept down through these factors.
