Abstract The study area (Green-Belt Project) locates in AL-Najaf Governorate in the coordinates (44o 10' 0"E & 44o 20' 0"E) and (32o 5' 0"N & 32o 15' 0"N). The study area has covering an area of about (90) km2, which contains many geological formations and represents part of Najaf-Karbala plateau. The project relies on ground water as sources of irrigation. The aim of this study is to evaluate the quality of ground water in the project area for irrigation and suitability to use in potable purposes. Directorate of agriculture in cooperation with Directorate of wells of Al-Najaf Al-Ashraf implemented five wells which is used as sources of irrigation in this project that identified as GFW1, 2, 3, 4 and 5 , respectively in this study. GFW4 and 5 are locate in semi confined Dammam formation and deeper then GFW1, 2 and 3 which located in unconfined Dibdiba. Eleven parameters as: pH, electrical conductivity, EC, total dissolved solids, TDS, sulfate ion, SO4-2, oil & grease, O&G, cadmium, Cd, lead, Pb, chromium, Cr, iron, Fe, copper, Cu, and zinc, Zn have been selected to determine water quality index (WQI) for irrigation and potable purposes according to maximum levels of standards
Different models of Water Quality Indices (WQIs) and Water Pollution Indices (WPIs) were considered as effective tools to assess the water quality and suitability for different purposes. Water and sediments samples were collected monthly from Dec., 2012 to Nov., 2013. Thirty-one water variables were measured to assess the water quality and degree of pollution. Some heavy metals in water and sediments, also TPHs, n-alkanes and PAHs were detected. According to GWQI, DWQI and IWQI ranges, the water can be classified as poor - marginal for general and irrigation use. According to NSF-WQI range the water classified as poor-unsuitable for drinking use. The water can be considered as medium - excellent for aquaculture use according to MOC-WQI range. TSI range referred to mesotrophy- eutrophy water, whereas water can be classified as very high trophic level according to TRIX range. OPI range referred to weak organic -non organic pollution status. HPI range referred to polluted water according to impermissible values of dissolved Pb, Fe and Cd. Source of n-alkanes was mainly biogenic and pyrogenic and at least petrogenic, while the source of PAHs compounds pyrogenic and petrogenic.