Using COP Method to Assessment of Karst Vulnerability in Izeh, south west Iran

Ali Mehrabinejad , Leila Mirzaei , Kazem Rangzan , Farshad Alijani

A vulnerability-based approach for delineating groundwater pollution potential zones in karst aquifer has been developed to implement Naal-e-Asbi karst aquifer protection regulations, south west Iran. The ‘COP method’ has been developed for the assessment of intrinsic vulnerability of Naal-e-Asbi karst aquifer. This method uses the properties of overlying layers above the water table (O factor), the concentration of flow (C factor) and precipitation (P factor) over the aquifer, as the parameters to assess the intrinsic vulnerability of groundwater. This method considers karst characteristics, such as the presence of swallow holes (C factor) and their catchments areas as well as karstic landforms, as factors which decrease the natural protection provided by overlying layers (O factor). The P factor allows for consideration of the spatial and temporal variability of precipitation, which is considered the transport agent of contamination. The P factor is evaluated by two subfactors: Quantity of precipitation and temporal distribution of precipitation. In the COP method, the effect of rainfall quantity and the annual recharge on groundwater vulnerability is described by the mean annual rainfall of a historical series of wet years. In this study the subfactor of quantity of precipitation then evaluated by minimum and maximum annual rainfall of a historical data to obtain the effects of lowest and highest recharge on the pollution potential in the karst aquifer. The results have been compared with nitrate concentrations in the Naal-e-Asbi karst aquifer. Comparisons with these data show the advantages of the COP method in the assessment of vulnerability of karstic groundwater.