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A LIMITATION OF USING EPIK METHOD TO DEFINE PROTECTION ZONES FOR KARST AQUIFERS

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Watershed Management to Meet Water Quality Standards and Emerging TMDL (Total Maximum Daily Load) Proceedings of the Third Conference 5-9 March 2005 (Atlanta, Georgia USA) Publication Date 5 March 2005  701P0105.(doi:10.13031/2013.18132)
Authors:   K. A. RASHED and G. PARKIN
Keywords:   Karst aquifer, Vulnerability, SHETRAN model, Pollution, Particle tracking, EPIK method, Protection zones

Groundwater in karst regions are very sensitive (vulnerable) to human activities. This vulnerability is related to the specific character of groundwater flow in karst aquifers, which is the presence of preferred pathways (pipe-like conduits) where contaminants can travel rapidly through the system. The physically based model SHETRAN was used to run particle-tracking simulations on a simplified hypothetical karst aquifer system. The objectives of the work were: Firstly, to simulate the aquifer system, with different model parameters (cases) to understand the sensitivity of each individual parameter on the particle movements within the aquifer as well as attempting to identify the most vulnerable parts of the aquifer to pollution. Secondly, to use the existing EPIK method to define protection zones for each case. The first case will be used as a reference case to compare the results with. In the second case the only parameter changed was the exchange coefficient between the surrounding matrix and pipe-like conduits. The hydraulic conductivity of the surrounding matrix was subjected to change in the third case. The obtained results show that any increase in the exchange coefficient or hydraulic conductivity of the matrix will enhance the chance that more particles will reach the outlet. The use of EPIK method on three different cases produced similar protection zones. This is because of the limitation of the EPIK method since it does not take in account the flow exchange between conduits and surrounding matrix as well as the variation of the hydraulic conductivity of the surrounding matrix.

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