Delineation of Wellhead Protection Plans for Municipal Supply Wells in Gaza Governorate

Abstract

Groundwater is the only source of fresh water in Gaza Strip while its inhabitants and its water consumption increased rapidly. This study aims at preserving and protecting the groundwater from any pollutants caused by industrial installations through the work of delineation of Wellhead Protection Areas (WHPA) for Municipal Supply Wells in Gaza Governorate boundaries. WHPA has been determined in three different methods: Calculated Fixed-Radius Method (CFR), Analytical Method (AM), and Wellhead Analytic Element Model (WhAEM2000) which is currently used by the United States Environmental Protection Agency (EPA). These methods mainly depend on the time it takes groundwater to travel a specified horizontal distance. Three well zones were delineated for each municipal production well, the first zone is 50 days time of travel (TOT), the second zone is 2 years TOT and the third zone is 5 years TOT. All industrial installations with high pollution that fall in the well zones were investigated. The exact location of 141 industrial installations that were previously adopted by Environment Quality Authority (EQA) were determined by using handheld Global Positioning System (GPS). Installation sites were located and signed on maps by using GPS. Results showed that when CFR method was used on total 2 industrial installations lie in WHPA for 50 days TOT where the average of the radius is about71 m, 13 industrial installations lie in WHPA for 2 years TOT where the average of the radius is about217 m, and 32 industrial installations lie in WHPA for 5 years TOT where the average of the radius is about429 m. From the results, it can be recommended that by using CFR method any industrial installation should be prohibited in any distance less than430 mfrom the well. Analytical Method showed that are no industrial installations lie in WHPA for 50 days TOT, 2 industrial installations lie in WHPA for 2 years TOT, and 10 industrial installations lie in WHPA for 5 years TOT. From the results, it can be recommended that by using analytical method, any industrial installation should be prohibited in any ellipse radiuses rmax, rmin, and rp less than862 m,150 m, and223 m respectively around the well. Sensitivity analysis for analytical method showed that there are no upper or lower limits on values of gradient, extraction rate, hydraulic conductivity, and aquifer thickness. The only witnessed anomalies are when using low values of effective porosity. If not using effective porosities smaller than 0.1 however, the calculation of r should be correct. Effective porosities smaller than 0.1 are uncommon for aquifers. Wellhead Analytic Element Model revealed that there are no industrial installations lie in WHPA for 50 days TOT, 3 industrial installations lie in WHPA for 2 years TOT, and 5 industrial installations lie in WHPA for 5 years TOT. From the results, it can be recommended that by using WhAEM2000 method any industrial installation should be prohibited in any boat shaped radiuses Lu, Ls and Ymax are454 m,79 m,250 m respectively around the well. CFR method is the weakest method because it does not take into account regional groundwater flow, causing a hydraulic gradient. WHPAs identified by these methods may be either too large or too small, resulting in wellhead overprotection or under protection. Analytical Method incorporates hydrogeologic characteristics of the aquifer, groundwater flow, and hydrogeologic boundaries into the model. Often produces a WHPA that is smaller than the one produced using CRF. WhAEM2000 method is the best method because it uses a hydrogeological computer model of groundwater flow and it provides a more accurate delineation of the WHPA. It often produces a smaller area to manage than other methods. Nahawnd Company for Plastic Industry has been selected as a case study were field visit was carried out to investigate the availability of the mitigation measures in the site. The company is very close to (R/25A, R/25B, R/25C, and R/25 D) well field. From this study it is clear that no mitigation measures have been identified as necessary to reduce the anticipated groundwater impacts of the industry. The study concluded that all the industrial installations located in the WHPA should be carefully checked and investigated by EQA. Mitigation measures for pollutants caused by these industrial installations should be identified. In addition, EQA must give licenses for the establishment of any new industrial installations based on the delineation of WHPAs using the previously mentioned methods.