ESTIMATION OF GROUNDWATER VULNERABILITY IN BAHR AL-NAJAF AREA, MIDDLE OF IRAQ

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1 International Journal of Civil Engineering and Technology (IJCIET) Volume 9, Issue 13, December 2018, pp , Article ID: IJCIET_09_13_179 Available online at ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed ESTIMATION OF GROUNDWATER VULNERABILITY IN BAHR AL-NAJAF AREA, MIDDLE OF IRAQ Ali H. Al-Aboodi Assistant Professor of Civil Engineering Dept. College of Engineering, University of Basrah. Iraq Zaid N. Hashim Ph. D. Student, Civil Engineering Dept. College of Engineering, University of Basrah. Iraq ABSTRACT Once contaminants reach the aquifer, the mitigation thereof becomes expensive and often not readily possible. A proactive approach to the assessment of aquifer vulnerability to contamination, rather than a reactive approach, is thus of utmost importance for the future sus-tainability of our groundwater resources. The main object of this study is to estimate the groundwater vulnerability in Bahr Al-Najaf area, middle of Iraq. Data in the present study were of two types: spatial data and nonspatial data, there are obtained from wells logs, pumping test results, geological maps and hydro-geologic reports, and soil investigations. The scope of pollution was analyzed by developing the seven map layers and generating the DRASTIC technique. The vulnerability index was obtained by DRASTIC technique that varied from (70 to 140). Key words: Bahr Al-Najaf, DRASTIC, Groundwater, Middle of Iraq, Vulnerability Cite this Article: Ali H. Al-Aboodi and Zaid N. Hashim, Estimation of Groundwater Vulnerability in Bahr Al-Najaf Area, Middle of Iraq, International Journal of Civil Engineering and Technology (IJCIET) 9(13), 2018, pp INTRODUCTION In dry regions of the world, groundwater is an invaluable prove-nance for water. If groundwater is contaminated, may cause an environmental degradation and health risk. Groundwater can be exposed for a wide range of activities or human actions that may lead to the leaching of pesticides and fertilizers, disposal of sewage, and waste materials. Prohibition of groundwater pollution is the best way to effective and efficient environmental administration, as the groundwater treatment is slow and costly. In order to conserve groundwater resources and areas exposed to pollution, as a result of human activities, must be editor@iaeme.com

2 Ali H. Al-Aboodi and Zaid N. Hashim identified, which can be best achieved by estimating the vulnerability of groundwater. [1]. Bahr Al-Najaf area considers as one of dry regions, and it is part from western desert which lack of surface water except in the north east section of the studied area. Therefore the area depends on groundwater (which consider the main source of water) to use it in different activities. In general, the expression "groundwater vulnerability" is employ to explain the essential features of the aquifer that limit whether it is possible to be influenced by an imposed contaminant load [1]. DRASTIC is the best, perhaps the most applicable vulnerability assessment scheme developed by the "US Environmental Protection Agency" (USEPA) by Aller [2]. There are no Bahr Al-Najaf area-wide maps showing areas that are vulnerable /or susceptible to contamination. "These maps have very fundamental benefits for examining existing and potential policies for groundwater protection" [3]. This study will be an important step in assessing exposure to pollution, and results will be merged with existing data to enable stakeholders and decision-makers to take the right decision regarding pollution prevention. 2. STUDY AREA The study area is located in the south western part of Najaf City, Figure (1), it is in fact part of the western plateau of Iraq. It covers an area of (2500) km 2. Study area extends between latitudes 31o 27' 57'' to 32 o 08' 29'' N and longitudes 43o 47' 02'' to 44o 32' 08'' E. Study area contains a lake with approximately area (48) km 2, this area increases at the rainy season, while the area of the lake de-creases during the summer. Bahr Al-Najaf is bounded from the north-east by Al-Najaf cliff (Tar Al-Najaf) that is a rocky cliff consists of rocks, sand, and clay. It represents a naturalistic extent of the alluvial plain in the form of the tongue extends towards the western plateau from the north to the south part of the Manathira town. Figure 1. The Study Area Location in Reference of Iraq Map 3. GEOLOGY AND HYDROLOGY OF STUDY AREA Based on the data collected, there is a fault (transversal fault) located right underneath the cliff (Tar Al-Najaf). ''The groundwater in this area does not have any connection with the groundwater on the eastern side and the groundwater that comes from the western part of the desert will emerge at this fault'' [4]. The fault in the study area named Abu Jir Fault. The upper part of the fracture (ground surface area) called Tar Al-Najaf. The aquifers stratification is created by the old ages of soil (old geological epochs) and based on the erosion that is occurred in ancient intervals [84]. these aquifers are Dammam Formation, Euphrates Formation (Early Miocene), Fat'ha & Nfayil formations (Middle Miocene) (Lower Fars), editor@iaeme.com

3 Estimation of Groundwater Vulnerability in Bahr Al-Najaf Area, Middle of Iraq Injana (Upper Fars Formation), Zahra Formation, area characteristic with flat relief which gradient slow toward north-east and there are several hills with karstification phenomena. Many factors like geological composition, the nature of sediments, and the climate situation, controlled in form of geological features in the desert area [5]. The recent form of earth surface due to from alternation of chemical and physical weathering process out of Quaternary period. These operations caused fracturing and cracking of rocks that occur in the area that lead to form Al-Sarier and Al-Hamad [6]. The direc-tion of groundwater flow generally is from south west to north east of study area. Despite of rainfall littleness in the desert area, especially in the study area, the Dammam confine aquifer recharge from rainfall through faults and fractures occurs at the western area toward Iraqi-Saudi border and occurs at the south-east of Saudi Arabia. Many studies conclude that most of Dammam water comes from source of old period which associated or followed of Dammam deposition [5]. 4. DRASTIC TECHNIQUE DRASTIC is an empirical groundwater technique that assessments groundwater pollution vulnerability of aquifer systems depended on the hydrogeological settings of that region. DRASTIC is an empirical groundwater technique that assessments groundwater pollution vulnerability of aquifer systems depended on the hydro-geological settings of that region [2]. A DRASTIC term was de-rived from the seven parameters, these are: Aquifer material (A), Impact of the vadose region (I) Depths to groundwater (D), Soil media (S), Recharge (R), Topography (T), and Conductivity (C). Every factor is divided into ranges and is allocated various ratings in a scale of 1 least contaminant inherent for 10 highest contami-nations inherent. The shape files were created with the aid of ESRI-GIS software (Arc Map 10.3) from features such as (geological, hydrogeological, soil map and hydro chemical data) in the study region. The DRASTIC ranking system encloses three main portions: Range, Rating, and Weight. The DRASTIC index determination for a specified region includes multiplying every factor weight by its rating and summing the entire. The higher total amount represents greater possibility for groundwater contamination, or greater groundwater vulnerability. For a specified region being estimated its vulnerability, each parameter is divided into ranges. Ranges for every DRASTIC factor are estimated with respect to the other factors so as to calculate the relative significance of each range with respect to contamination possibility. The numerical weights and ratings, which were recognized utilizing the Delphi method, are well defined and have been utilized universal. Delphi method uses the real and study practices of professionals in the region of concern to calculate grades of hazard. The last map of vulnerability is depended on the DRASTIC index (DVI) which is calculated as the weighted summation overlay of the seven sheets utilizing the next linear equation: DVI = Dw Dr + Rw Rr + Aw Ar + Sw Sr + Tw Tr + Iw Ir + Cw Cr.. (1) Where: Dr, Rr, Ar, Sr, Tr, Ir, and Cr: Rating for the depth to water table, aquifer recharge, aquifer media, the soil media, topographic (slop), vadose zone, and hydraulic conductivity. Dw, Rw, Aw, Sw, Tw, Iw, Cw: Weights assigned to the depth to water table, aquifer recharge, aquifer media, soil media, topography, vadose zone, and hydraulic conductivity. 5. MATERIAL AND SOURCE OF DATA The availability of input data is the corner stone of how to choose the appropriate technique as the absence or insufficient input in-formation into the technique is applied difficult [8].In the study area, information which are essential for calculation of DRASTIC ratings are acquired from wells logs, pumping test results, geological maps and hydro-geologic reports of MWR (ministry of water resource) archives of groundwater directorate in Al-Najaf government, editor@iaeme.com

4 Ali H. Al-Aboodi and Zaid N. Hashim Najaf meteorological station, and soil survey). Data in the present study were of two kinds: spatial information and non-spatial information. Spatial information was taken from maps, satellite imageries, etc. They could be directly digitized into GIS environment. Non-spatial information was the tabular information taken from tables, points, lists, etc. and this data could be stored in the database Depth to groundwater This factor denotes the depth from the earth surface to the water table of groundwater, and it gives a notion that the short distance will be leads to the contaminants move to the saturated region, while the deeper water table will be the lesser chances of contaminants to interact with groundwater. The groundwater level was measured by (21) wells. These data were used in the GIS environment by interpolating them to construct depth to water table map as a raster format. The Inverse Distance Weighted (IDW) used to interpolate the data, Figure (2). The depth of groundwater varied from (1) to more than (21) m Net recharge This parameter supplies data on the quantity of water which infil-tration to the saturated region. It is significant factor because the water which reaches to groundwater is a conveyor of pollutant. It is the amount of water/unit area of land that penetrates the ground surface and reaches the water table. CMB (Chloride Mass Balance) method is commonly utilized and is an active method for assessing groundwater recharge in semi-arid and arid regions [9]. Calculation of groundwater recharge is achieved by utilizing a mass-balance of the conservative chloride ion. The mass-balance uses three factors; the chloride concentration dissolved in rainfall, the annual volume of rainfall, and the chloride concentration dissolved in groundwater. Precipitation data was collected from Meteorological Agency of Iraq for the study area based on Meteorological Station of Najaf. The total average of annual precipitation is about (mm) for the period ( ). Precipitation chloride content was analyzed depending on the collected rainfall samples in March, April, May, November, and January for ( ) for three location points. The chloride concentrations in groundwater in selected wells distributed over the study area. Determination of chloride concentration has been accomplished by titration. Figure (3) represents the value of net recharge of Groundwater depending on the chloride concentrations values. The average annual recharge is estimated by using CMB, where its value was equal to (19.27) mm/year. Figure 2. The Depth of Groundwater. Figure 3. The Net Recharge of Study Area editor@iaeme.com

5 Estimation of Groundwater Vulnerability in Bahr Al-Najaf Area, Middle of Iraq 5.3. Aquifer media The aquifer material type limits the mobility of the pollutant through it. This increases the contaminant attenuation due to increases in the travel time of pollutant through the aquifer. It is the possible region for water storing, the pollutant dilution of aquifer based on the quantity and sorting of fine grains, lesser the grain size higher the dilution ability of aquifer material. The results of this parameter was depended on the geological map of the area and drilling well logs to produce the polygon distribution of the area. Two sections of the aquifer material was classified in the studied area which are limestone in the northeast, and northeast of the basin ;( marly, chalky) limestone in the central and southern part, Figure (4) Soil media This factor signifies the upper part of the vadose region that identify by biological activities. The aquifer media and soil media determine the amount of infiltration water to the groundwater. Soil with clays and silts has greater water holding ability and so increase the moving time of the pollutant over the roots zone. Soil material is the highest and weathered portion of the ground; soil cover features effect the downward and surface movement of pollutants. Twelve soil samples borehole were selected above the study area in depth of 0.3 m. Sieves analysis test, and Hydrometer test was conducted for these samples to determine the grain size distribution curves. Divide the study area into diverse regular units depended on the visual observation and eliminate the surface litter at the specimen spot. Four various soil media was founded in the area based on Soil Survey, soil media was classified into (clay loam, silty loam, loam, and sandy loam), Figure (5). Figure 4. The Aquifer Media Map Figure 5: The Soil Media Map 5.5. Topography This parameter represents the slope of earth. Regions by small slopes tend to save water longer. This leads larger filtration of recharge water and larger emigration of pollutant. Regions with steep slopes, tend to have a big amount of runoff and lesser amount of percolation and minimal vulnerable of groundwater pollution. Figure (6) shows the Digital Elevation Model (DEM) with 30 m pixel size map of study region. Slope was intended in expression of ratio utilizing the resampled version of the original digital elevation model[10]. Tool was executed to create slope map in Arc Map (10.3) by the algorithm of slope computation, where the elevation variance divided to the space between the points. Then, mean amount of the slopes is established as a result amount. Made grid surface is reclassified based on slope index ranges. The ratios of the point s information which are reclassified are editor@iaeme.com

6 Ali H. Al-Aboodi and Zaid N. Hashim rated as explained in DRASTIC technique. As a outcome of the above efforts topography rating map is acquired as defined in DRASTIC technique as shown in Figure (7). Figure 6. Topography of Study Area Figure 7. The Topography Map 5.6. Vadose zone This factor denotes the unsaturated region upper the water table. The vadose zone texture limits the time of movement of the pollu-tants through its. Its impact on aquifer contamination potential alike to that of soil cover, based on its permeability, and on the dilution features of the media. This parameter was obtained utilizing burrowing process profiles of directorate of groundwater. These profiles were utilized to encode the geological units according to the DRASTIC technique rating system. Fine media was assigned a low rating value compared to the coarse media types. Vadose zone soil media was developed from the cross-sections of lithological acquired from (17) vertical cross sections. Three segments of vadose zone was comprised (shale, limestone, sand and gravel) occupying area of (8%, 41% and 51%) respectively, Figure (8) Hydraulic conductivity This parameter determines amounts of water infiltrating to the groundwater over the aquifer. For very leaky soils, the movement time of contaminant is reduced within the aquifer. It mentions to the aptitude of the aquifer structure to convey water; an aquifer with high conductivity is vulnerable to significant pollution as a plume of pollution can passage simply over the aquifer. The value of hydraulic conductivity from pumping test results of Ministry of Water Resource (MWR) archives of groundwater directorate in Al-Najaf government over the study region. The hydraulic conductivity varies between (2.5-9) m/day, Figure (9) editor@iaeme.com

7 Estimation of Groundwater Vulnerability in Bahr Al-Najaf Area, Middle of Iraq Figure 8. The Vados Zone Map Figure 9. Hydraulic Conductivity Map 6. RESULTS AND DISCUSSION The definitive vulnerability was acquired by implementation the technique in the environment of GIS by utilizing the seven data layers. The DRASTIC scores acquired from the technique ranged from (70 to 140). The mean value of DRASTIC index for all study area is (109). Table (1) shows the DRASTIC results in terms of scaling, and percentage of each zone of vulnerability. Figure (10) also; delineate spatial vulnerability of groundwater in the study area. The map marks out areas with varying sensitivity (very low, low, and moderate) based on Aller classification [2]. The demarcated area is relative indication of susceptibility of groundwater to pollution from diffuse sources. With reference to table (1), about 65.6% of study area is classified under low vulnerability; the re-maining 28.16% and 6.24% are under very low and moderate vulnerability respectively. Figure (10) shows the spatial distribution of moderate, low and very low vulnerability in the studied area. It seems that southern part, the surrounding of the lake east of study area, and small strips of middle area are very low vulnerable areas. The majority of study areas are of low vulnerability. The remaining area is moderately vulnerable. Table (2) display the statistical synopsis of the seven parameters rated and processed using the GIS technique so as to get the vulnerability of study area for contamination. In order to check out the interdependence of the rated seven factors of the DRASTIC technique, order correlations for (21) rank of Spearman are calculated. Number of correlations = n (n-1)/2 (where n: is the numeral of factors =7) as per table (3). Out of these (21) correlations, twelve are very weak, two are weak, six are moderate. 67% of total relations computed by Spearman formula showed weak correlations, so; this leads that factors are largely independent and there is small hazard of mis-adjustment in the definitive index editor@iaeme.com

8 Ali H. Al-Aboodi and Zaid N. Hashim Figure 10 Spatial distribution of Groundwater Vulnerability for Study Area by Using DRASTIC Technique. Table 1 The Percentage of Vulnerability for Each Zone Vulnerability Zone From To Area (hectar) Percentage ratio Very low % Low % Moderate % Total % Table 2: The Statistical Synopsis of the Seven Factors. Parameters D R A S T I C Weights Min Max Mean SD* CV** 33% 0% 0% 30% 3% 22% 25% Rank of Mean Rank of CV * Standard Deviation ** Coefficient of Variation = SD/Mean Table 3 Correlation Coefficient Matrix for the Seven Parameters. D R A S T I C D 1 R A S T I C editor@iaeme.com

9 Estimation of Groundwater Vulnerability in Bahr Al-Najaf Area, Middle of Iraq 7. CONCLUSIONS The vulnerability index was obtained by the DRASTIC technique that varies from (70 to 140). The mean value of DRASTIC index for all study area is (109). About 65.6% of study area is classified under low vulnerability; the remaining 28.16% and 6.24% are under very low and moderate vulnerability respectively. The parameters means shows that the highest impact to the index of vulnerability is produced by Topography (mean = 9.92). The Influence of vadose region is next (mean = 6.78) and so on for Aquifer media, Depth, and Soil. Hydraulic conductivity and Recharge having means of 1.75 and 1 contribute lowest to the pollution of groundwater. The variations coefficient point to that a high impact to the vulnerability index variation is produced by Depth to groundwater (33 %), then by Soil (30 %).(67%) of total relations computed by Spearman formula showed weak correlations, so it means that parameters are largely independent and there is little risk of miss-adjustment in the final index. ACKNOWLEDGEMENT The authors would like to thank technical cadres in the laboratories of both the Faculty of Engineering University of Kufa and the Department of Environment in the province of Najaf to provide technical support. REFERENCES [1] National Research Council (NRC), "Ground water vulnerability assessment, contamination potential under conditions of uncertainty", National Academy Press(Washington, D.C.-USA), (1993). [2] Aller, L., Bennett, T., Lehr, J.H., Petty, R.J. and Hackett, G.. 'DRASTIC: A standardized system for evaluation groundwater pollution potential using hydro-geologic setting'. EPA- 600/ Ada, Oklahoma: U.S. Environmental Protection Agency. 228,(1987). [3] Stenemo, F., 'Vulnerability assessment of pesticides leaching to groundwater',, Journal of Contaminant Hydrology, Dept of Soil Science, SLU. Acta university Sueciae, vol. (2007):. [ online]27-apr-07, [Cited:24-Feb-08] available: Stenemo.pdf [4] Al-Furat Center for Studies and Engineering Designs. The technical report of drilling wells in the Western Desert - Bahr An- Najaf, Baghdad, Iraq (1992). [5] Waierdy, N.W. ''The Hydraulic characteristic of the Dammam Formation in the western desert of Iraq''.Unpublished Ms. Thesis, college of Science, University of Baghdad. (1994). [6] Al-Ani, ' The regional geological mapping of south west of Busaiya area, report No. 1346, Geol. Sur. Min. Inves., Baghdad, Iraq. (1983). [7] Barwary A. M. and Nasira, A. S. Geological map of Al-Najaf quadrangle sheet NH-38-2 of scale 1: st. ed. Iraq: General Commission for Geological Survey and Mining, (1996). [8] Hahn, L., 'A groundwater vulnerability to pesticides map for Indiana',, Water Quality Program Specialist, Pesticide Section,, Office of Indiana State Chemist, STATE OF INDIANA.[ online]04-aug-97, [Cited:14-Jan-08] available: ( 1997). [9] Scanlon BR, Keese KE, Flint AL, Flint LE, Gaye CB, Ed-munds WM, Simmers I, Cook P. Global synthesis of groundwater recharge in semiarid and arid regions. Hydrol Process.;20: ( 2006). [10] Elci, A., 'Groundwater Vulnerability Mapping Optimized With Groundwater Quality Data: The Tahtali Basin Example, Balwois 2010', Water Observation and Information System for Decision Support Congress Ohrid Republic of Macedonia (2010) editor@iaeme.com