Evaluation of multiple aquifer vulnerability using DRASTIC, SINTACS methods

Document Type : Research paper

Author

University of Tabriz

Abstract

 
Evaluation of multiple aquifer vulnerability using of DRASTIC, SINTACS frameworks
 
 
1. Introduction
Nowadays, the issue of freshwater supply is the main concern of researchers in the arid and semi-arid countries like Iran. Available water resources are necessary to be protected against pollution due to arid climate and frequent droughts and lack of water resources. One of the ways to protect groundwater against pollutants is to identify the areas with high potential of pollution. The quality of groundwater and surface water resources of Varzeqan plain can also be affected by the wastewater from the Sungun Copper Mine, which is impounding in tailing dam the north of Varzeqan plain. The groundwater flow direction is from west to east which thought to coincide with the surface water flow direction. The theory of groundwater vulnerability was first introduced in the 1960s in France to create an alertness of groundwater contamination. Several studies were carried out in different parts of the world to assess the pollution and vulnerability of groundwater. Many approaches have been developed to evaluate aquifer vulnerability. They include process-based methods, statistical methods, and overlay and index methods. One of the most common frameworks for assessing the vulnerability is the DRASTIC and SINTACS. The DRASTIC framework was developed by the National Groundwater Association (NGWA) in collaboration with the United States Environmental Protection Agency (USEPA). The SINTACS method used in this study was developed to evaluate relative groundwater pollution vulnerability using seven hydrogeologic parameters. In this paper, to assessment aquifer intrinsic vulnerability, a point count system framework called SINTACS and DRASTIC was selected, Also, in this study, the Corrected SINTACS framework has been introduced for the first time in assessing the vulnerability of confined aquifer.
 
2. Materials & Methods
Hydrogeological, geological characteristics of the study area
The results of geophysical study and exploratory wells, piezometer and observation logs prepare evidence to identify two types of aquifers: alluvium aquifer including unconfined (with approx. 150 km2) and confined (with approx. 57 km2) aquifers. Confined aquifers surrounding by the unconfined aquifer and hence multiple aquifers and just alluvium aquifer located in the plain. The aquifers within the study area are a complex system and comprise two confined aquifers, surrounded by one unconfined aquifer. Varzeqan alluvium aquifers classified into three main hydraulic conductivity sections (i) High hydraulic conductivity (about 90 m/d) area in the eastern part of the plain composed of coarse-grain size sedimentary; and (ii) Moderate hydraulic conductivity (about 25 m/d) area in the central part of the plain composed of sand, gravel, and silt grains; and (iii) Low hydraulic conductivity (about 8 m/d) area in the western part of the plain composed of  silt, clay and slightly sand.
 
DRASTIC framework
 
DRASTIC is an acronym of seven hydrogeological parameters comprises depth of groundwater (D), net recharge (R), aquifer media (A), soil media (S), topography (T), impact of vadose zone (I) and hydraulic conductivity (C). Each of these parameters is assigned a rate and a weight according to their relative importance. To prepare a vulnerability map, the required data of various parameters are given to ArcGIS software package in order to perform GIS processing, then, the vulnerability map is prepared. The overall DRASTIC vulnerability index (DVI) is calculated using Eq. 1. As follows,
 
DVI = DwDr + RwRr+ AwAr + SwSr + TwTr + IwIr + CwCr                                                                     (1)
 
Where D, R, A, S, T, I, and C represent the DRASTIC parameters, and the r and w subscripts correspond to the rates and weights respectively.
 
SINTACS framework
 
SINTACS is an updated model of DRASTIC frameworks and includes seven parameters such as water table depth (S), net recharge (I), unsaturated zone (vadose zone) (N), soil media (T), aquifer media (A), hydraulic conductivity (C) and topographic slope (S).The SINTACS is similar in type and number of parameters to the DRASTIC model, but the rates and weights of this framework are different from the DRASTIC. Vulnerability index is calculated using Eq. 2.
 
ISINTACS= ∑7 i=1 Pi*Wi                                                                                                                (2)
 
Where ISINTACS is the SINTACS vulnerability index, Pi is the rating of each parameter and Wi is the relative weight of SINTACS parameters.
 
Corrected SINTACS framework
 
In this study, Corrected SINTACS framework is presented for the first time to assess the vulnerability of confined aquifer that mechanism of this framework is derived from DRASTIC in the evaluation of confined aquifer and how to rate and assign the weight of the proposed framework, such as SINTACS in unconfined aquifer. DRASTIC and SINTACS differ from Corrected SINTACS for confined aquifer in the process of preparing the layers and the difference in rating for this framework.
 
3. Discussion of Results
 
Results of DRASTIC, SINTACS and Corrected SINTACS frameworks
 
The objectives formed for the present study involve carrying out intrinsic vulnerability assessment using DRASTIC and SINTACS frameworks to priorities area according to their vulnerability to contamination. After preparing the raster layers of the frameworks, these layers were combined using the Raster Calculator command in the ArcGIS software and final vulnerability map was obtained. The vulnerability index based on DRASTIC in unconfined aquifer, varied in the range of 91 to 160 and for confined aquifer of 48 to 93, That's unconfined aquifer 33, 59, 8% of the study area is located in areas with low, medium and high vulnerability, respectively and for confined aquifer, 26%, 53%, 21%, respectively, are located in areas with low, medium and high vulnerability. The results of the evaluation with SINTACS framework for unconfined aquifer showed a number between 123-188, based on this, 12, 53 and 35% of the plain are located in areas with low, medium and high vulnerability, respectively. In assessing the confined aquifer using corrected SINTACS, the vulnerability index range was between 80-133.
 
Validation
 
In order to find out more accurately and compare the frameworks in this study, the correlation coefficient between vulnerability maps and nitrate data was calculated. Nitrate concentration data were used to validate the frameworks used in the study area separately for both types of aquifers, that is for unconfined aquifer, the results show a relative correlation with the value of R2 equal to 0.59 and 0.24 for DRASTIC and SINTACS, respectively. The value of the correlation coefficient in confined aquifer, for Corrected SINTACS and DRASTIC is 0.55 and 0.3, respectively. The CI between vulnerability maps and nitrate concentration were used for validation of the frameworks. The results show that DRASTIC and Corrected SINTACS have higher CI for the unconfined and confined aquifer, respectively. To more accurately assess and select the best vulnerability assessment framework for both types of aquifer, the (CI) method was used.
.
4. Conclusions
 
The purpose of this study was to determine the intrinsic vulnerability in multiple aquifer of Varzeqan plain using DRASTIC and SINTACS frameworks and finally, to compare the efficiency between them. In this study, simultaneous assessment of the intrinsic vulnerability of two aquifers confined and unconfined of Varzeqan plain and the determination of areas with contamination potential based on the hydrogeological conditions of the study area has been investigated. In this study, Corrected SINTACS has been proposed to assess the vulnerability of confined aquifer. Varzeqan multiple aquifer vulnerability index indicates that this aquifer is classified the capability of the contamination potential is in the medium to high range that in the unconfined aquifer due to the low water table depth, lower thickness of the unsaturated region and high hydraulic conductivity and for the confined aquifer due to the thickness of the impermeable layer. To assess the ability of frameworks in both aquifer, in fact, (R2) and (CI) were used to validate the frameworks.
The results showed that DRASTIC with higher correlation coefficient (R2) and correlation index (CI) values than SINTACS values is the better framework to vulnerability assessment of unconfined aquifer in Varzeqan plain. However, Corrected SINTACS have higher performance than DRASTIC for confined aquifer. In determining the vulnerable points of the confined aquifer, the most important factor is the thickness of the impermeable layer (clay and silt), whatever this layer is thicker, the possibility of contaminant transfer is less and as a result, the vulnerability index values will decrease.
 

Keywords


اصغریمقدم،ا.،فیجانی،ا.،ندیری،ع.،1388. ارزیابیآسیب‌پذیریآبزیرزمینی دشت‌هایبازرگانوپلدشتبااستفادهازمدلدراستیکبراساس .GIS   محیط‌شناسی، شماره52،52-64.
قره خانی، م.، ندیری، ع.، اصغری مقدم، ا.، صادقی اقدم، ف.، بهینه‌سازی مدل دراستیک با استفاده از ماشین بردار پشتیبان و شبکه عصبی مصنوعی به منظور ارزیابی آسیب­پذیری ذاتی آبخوان دشت اردبیل. اکوهیدرولوژی،شماره 3، 324-311
مهرپرتو،م.،امینی فضل، آ.، رادفر، ج.،1371.نقشهزمین­شناسی1:100000ورزقان.سازمانزمین‌شناسیواکتشافاتمعدنیکشور.
برزگر، ر.، 1392. ارزیابی کیفیت و کمیت منابع آب زیرزمینی دشت تبریز. پایان‌نامه کارشناسی ارشد، دانشکده علوم طبیعی، دانشگاه تبریز.
مهندسین مشاور یکم، 1388. گزارش و مطالعات نیمه تفصیلی آب‌های زیرزمینی دشت‌های تحت پوشش شرکت سهامی آب منطقه‌ای آذربایجان شرقی در محیطGIS . مطالعات آب­های زیرزمینی محدوده مطالعاتی اهر-ورزقان، 208.
Aller, L., Bennett, T., Lehr, J., Petty, R., Hackett, G., 1987. DRASTIC: A standardized system for evaluating ground water pollution potential using hydrogeologic settings. Ada, Oklahoma, U.S. and    Environmental Protection Agency.
Antonakos, A.K., and Lambrakis, N.J., 2007. Development and testing of three hybrid methods for the assessment of aquifer vulnerability to nitrates based on the drastic model, an example from NE Korinthia, Greece. Journal of Hydrology,288– 304.
Almasri, M., 2008.  Assessment of intrinsic vulnerability to contamination for Gaza coastal aquifer Palestine. Journal of Environmental Management, 88-577-593.
Al kuisi, M., El-Naqa, A., and Hmmouri, N., 2006. Vulnerability mapping of shallow groundwater aquifer using SINTACS model in the Jordan Valley area, Jordan. Environmental Geology, vol 50, 651- 667.
Babiker, I.S., Mohamed, M.M.A., Hiyama, T & KatoK., 2005. A GIS-based DRASTIC model for assessing aquifer vulnerability in Kakamigahara, Heights, Gifu Prefecture, central Japan. Science of the Total Environment, 345, 127–140.
Boughriba, M., Barkaoui, A., Zarhloule, Y., Lahmer, Z., El-Houadi, B., Verdoya, M., 2009. Groundwater vulnerability and risk mapping of the Angad transboundary aquifer using DRASTIC index method in GIS environment. Arabian Journal of Geoscience. 3, 207-220.
Corniello, A., Ducci, D., and Napolitano, P., 1997. Comparison between parametric methods to evaluate aquifer pollution vulnerability using a GIS: An example in the Piana Campana. Engineering Geology and the Environment, Balkema, Rotterdam, The Netherlands, 1721-1726.
Evans, BM., Myers, WL. A., 1990. GIS-based approach to evaluating regional groundwater pollution potential with DRASTIC. J SoilWater Conserv, 45, 242– 5.
Fijani, E., Nadiri, A.A., Asghari Moghaddam, A., Tsai, FT-C., and Dixon, B., 2013. Optimization of DRASTIC Method by Supervised Committee Machine Artificial Intelligence to Assess Groundwater Vulnerability for Maragheh-Bonab Plain Aquifer, Iran. Journal of hydrology, 530,89-100.
Majandang, J., and Sarapirome, S., 2013. Groundwater vulnerability assessment and sensitivity analysis in Nong Rua, Khon Kaen, Thailand, using a GIS-based SINTACS model. Environ Earth Science, 68, 2025–2039.
Nadiri, A.A., Sedghi, Z., Khatibi, R., Gharekhani, M., 2017. Mapping vulnerability of multiple aquifers using multiple models and fuzzy logic to objectively derive model structures. Science of The Total Environment. 593-594, 75-90.
 
Nadiri A.A, Sedghi Z, Khatibi R, Sadeghfam S., 2018a. Mapping Specific Vulnerability of multiple confined and unconfined aquifers by using artificial intelligence to learn from multiple DRASTIC frameworks. Journal of Environmental Management, 415-428.
Nadiri A.A, Gharekhani M, Khatibi R., 2018b. Mapping Aquifer Vulnerability Indices using Artificial Intelligence-running Multiple Frame works (AIMF) With Supervised and unsupervised Learning. Water resource Management, 32(9), 3023-3040.
Nadiri A.A, Norouzi, H., Khatibi, R., Gharekhani, M., 2019. Groundwater DRASTIC Vulnerability Mapping by Unsupervised and Supervised Techniques Using a Modelling Strategy in Two Levels. Journal of Hydrology,574, 744-759.
Sadeghfam S., Hassanzadeh, Y., Nadiri A.A, Zarghami, M., 2016. Localization of Groundwater Vulnerability Assessment Using Catastrophe Theory. Water resource Management, 30, 4585-4601.
Niknam, R., Mohammadi, K., and Majd, VJ., 2007. Groundwater Vulnerability Evaluation of Tehran-Karaj Aquifer Using DRASTIC Method and Fuzzy Logic. Iran Water Resources Research, 2, 39-47.
Panagopoulos, G., Antonakos, A., and Lambrakis, N., 2005. Optimization of DRASTIC model for groundwater vulnerability assessment by the use of simple statistical methods and GIS. Hydrogeology Journal (published online).
Rosen, L., 1994. A study of the DRASTIC   methodology with emphasis on Swedish conditions. GroundWater, 32(2), 278 –85.
Stigter, TY., Ribeiro, L., and Carvalho, D. A. M. M., 2006. Evaluation of an intrinsic and a specific vulnerability assessment method in comparison with groundwater salinisation and nitrate contamination level in two agriculture regions in the south of Portugal. Hydrogeology, 14, 79-99.
Samey, A.A., Gang, C., 2008. A GIS Based DRASTIC Model for the Assessment of Groundwater Vulnerability to Pollution in West Mitidja: Blida City Algeria. Research Journal of Applied Sciences, 3(7), 500-507.
Vrba, J., and Zoporozec, A., 1994. Guidebook on mapping groundwater vulnerability, International Contributions to Hydrogeology. Verlag Heinz Heise GmbH and Co, KG.