Journal of Earth Science, Vol. 31, No. 5, p. 993–1006, October 2020 ISSN 1674-487X Printed in China https://doi.org/10.1007/s12583-020-1293-y Contribution of Hydrogeochemical and Isotopic Tools to the Management of Upper and Middle Cheliff Aquifers Madene Elaid , Meddi Hind *, Boufekane Abdelmadjid, Meddi Mohamed National Higher School for Hydraulics, LGEE-ENSH Blida, Algeria Madene Elaid: https://orcid.org/0000-0002-7860-9188; Meddi Hind: https://orcid.org/0000-0001-6592-304X ABSTRACT: In the alluvial aquifers of Upper and Middle Cheliff (North-West Algeria), the groundwater quality is deteriorating. The objective of this study was to characterize the physical and chemical prop- erties of these aquifers; and to evaluate the groundwater quality and its appropriateness for drinking and agricultural use. An investigation was carried out by estimating of the physiochemical parameters (Ca2+, 2+ + + - 2- - - - Mg , Na , K , Cl , SO4 , HCO3, NO3, Br and TDS) to identify the chemical characteristics of groundwater. Morever, the isotopic composition was examined to identify the sources of recharge of these aquifers. The groundwater geochemistry for the high water level (May, 2012 and June, 2017) and low water level (No- vember, 2012 and October, 2017) was studied. Accordingly, water samples from 39 water sampling points were collected (October, 2017 and June, 2018), for the purpose of analyzing stable isotopes (18O, 2H). The results show that the groundwater is mainly characterized by Ca-Cl and Na-Cl type. The chemical quality of the water is from fair to poor with the presence of nitrates used in agricultural and urban discharge. Also, the Br/Cl ratio gives indications on the origin of the salinity. This salinity is due to the leaching of chlorinated fertilizers, the dissolution of evaporite deposits and the rise of deep salty water by the fault of Chellif. While, the diagram of δ2H=f(δ18O) indicates that the origin of the recharge of these aquifers is the Atlantic and Mediterranean oceanic meteoric rainwater. KEY WORDS: hydro-chemistry, management, isotopic analysis, groundwater, Upper and Middle Cheliff, Algeria. 0 INTRODUCTION origin of geochemical groundwater can be traced and distinguish Groundwater is the second largest reservoir of freshwater, the origin of groundwater salinity using a stable isotopic composi- after glaciers, lakes and rivers, with volumes of the order 8 to tion. This approach has been used by many researchers around the 10 ×106 km3 potentially exploitable (UNESCO, 1978), making world (Beal et al., 2019; Ogrinc et al., 2019). There was also dis- up 30% of the resources of drinking water (Gleick, 1996). How- cussion of studying water quality in our study area based on the ever, this resource, which used to be in good quality, is now most characteristic elements to determine the potability of this threatened by various points and diffuse sources of contamina- groundwater. This approach has been widely used in various ba- tion. The distribution of water between the layers of the earth sins around the world (Wali et al., 2019; Wright et al., 2019; Zheng varies in space and time. Knowledge of the hydrological func- et al., 2019; Cheng et al., 2017). tioning of aquifers and the geochemistry of groundwater is cru- The distinction between the different mechanisms of salini- cial for assessing the quality and natural tracing of water using zation makes it possible to reconstruct the origin of ground wa- the isotopic composition. The natural chemical composition of ters as well as their pathways, and to imagine their future evolu- groundwater responds to determinism partly due to the litholog- tions. Among the geochemical criteria which can help identify ical nature of aquifers and superficial terrains traversed by wa- the intrusion of surface or deep water as opposed to other sources ter (Blum et al., 2001). of salinity in the aquifer, such as chemical elements (cations, an- Historically, the groundwater chemistry of Upper and Mid- ions and dry residue) and ionic ratios, such as Na+/Cl-, Br-/Cl-, dle Cheliff has attracted the attention of many researchers. Most Ca2+/Mg2 + and also the stable isotopes 18O and 2H ((Chenaker et of these studies have focused on the interaction between ground- al., 2018; Belkoum and Houha, 2017; Trabelsi et al., 2007)). This water and bedrock with a fundamental control on the chemical approach was used by Mehr et al. (2017), Zhao et al. (2016) and characteristic of groundwater (Bemiloud, 2017; Touhari, 2015; Ma et al. (2014). Bouzelboudjen, 1987), which led to the idea used in this study: the The use of bromide anion contents is an essential comple- ment to chloride measurements in order to explain the salinity *Corresponding author: [email protected] anomalies in groundwaters. Br=f(Cl) and to the molar ratio © China University of Geosciences (Wuhan) and Springer-Verlag Br/Cl, it allows marine influence areas(the ocean, precipitation) GmbH Germany, Part of Springer Nature 2020 to be distinguished from evaporitic or anthropogenic influence areas (Farid et al., 2015). Manuscript received November 11, 2019. The objective of this article is to understand the mineraliza- Manuscript accepted March 15, 2020. tion process and the hydrodynamics of the groundwater of the Elaid, M., Hind, M., Abdelmadiid, B., et al., 2020. Contribution of Hydrogeochemical and Isotopic Tools to the Management of Upper and Middle Cheliff Aquifers. Journal of Earth Science, 31(5): 993–1006. https://doi.org/10.1007/s12583-020-1293-y. http://en.earth- science.net 994 Madene Elaid, Meddi Hind, Boufekane Abdelmadjid and Meddi Mohamed Upper and Middle Cheliff alluvial aquifers using chemical tools and a significant reduction of the alluvial aquifers. Water re- (major elements) and isotopic (18O and 2H). Then, a simulation sources are not only subject to overexploitation, but also to a tool based on the combination of the two geochemical and iso- degradation of their quality due to wastewater discharges and topic approaches is used to highlight the main plausible reaction salinization resulting from the leaching of evaporite formations mechanisms responsible for the mineralization, and the apparent occurring after the earthquake of October 10, 1980 by an im- age of the water. The variation of the isotopic composition is a portant surface faulting. Indeed, this tectonic accident released very useful indicator of the origin and nature of the resource. Fi- deep water, and allowed their rise towards the alluvial water ta- nally, the origin of water masses that recharge the aquifer and ble in the region of El Attaf (Middle Chellif water table), which specify the mechanisms of this recharge is defined. These eval- belongs to the sub-basin of the Tikazale wadi (IFES, 2002). uations are crucial for sustainable exploitation in a semi-arid re- These elements (interaction between deep salt water and alluvial gion with very limited groundwater resources. groundwater, uncontrolled urban discharges, the return of irriga- tion water and over-exploitation of groundwater for irrigation 1 STUDY AREA purposes) modify the chemistry of the water and make it unsuit- 1.1 General Overview of the Study Area able for the desired uses. The Upper and Middle Cheliff Basin, which is located in The study area is composed, according to the orohydro- north western Algeria and occupies the north-east of the Cheliff graphic delimitations, of 11 sub-basins. They are drained by the Basin, has undergone significant agricultural development in re- Cheliff wadi which crosses them for a length of about 349 km. cent years (Fig. 1). It covers 10 916.60 km2 (ANRH Blida, 2017). The groundwater resources of the Upper and Middle Che- The plains of Upper and Middle Cheliff are characterized liff plains have been assessed within the framework of the Na- by a semi-arid climate with Saharan influences in summer and tional Water Plan (1971). This evaluation is based on the hydro- Mediterranean influences in winter. The rainfall distribution is geological studies conducted by ANRH and the rain/infiltration very spatially marked. North of the study area, interannual pre- method. These plains are composed of coarse alluvium and oc- cipitation is very important on the southern slopes of the Dahra cupy an area of 1 070 km2 (Upper Cheliff: 370 km2, Middle East- and Zaccar mountains, with an interannual average of more than ern Cheliff: 360 km2, Middle Western Cheliff: 340 km2), whose 600 mm. Precipitation decreases in the plains of Upper and Mid- potential in groundwater is estimated at 43 Hm3/year (DHW, dle Cheliff where it varies between 300 and 400 mm. The total 1971) (Upper Cheliff: 16 Hm3/year, Middle Eastern Cheliff: 16 annual potential of evapotranspiration ranges from 1200 mm to Hm3/year, Middle Western Cheliff: 11 Hm3/year). This water 1 600 mm, more than double of the total rainfall. The Upper and potential is the first source for water supply and irrigation. The Middle Chéliff Basin is characterized by an average interannual latter, combined with drought, caused drying up of the springs temperature oscillating from 13 to 20 °C. Figure 1. Geographical location, geology of the study area and geological sections across the Upper and Middle Cheliff Basin. Contribution of Hydrogeochemical and Isotopic Tools to the Management of Upper and Middle Cheliff Aquifers 995 1.2 Geology plain of El Abadia-Amra or the plain of Middle Eastern Cheliff; The upper and middle Cheliff watershed is located in the the plain of Chlef or the plain of Middle Western Cheliff. Tell Atlas of Algera and corresponds to a subsident intra- The Cheliff Basin is a Neogene post-nappe basin. The Tel- mountainous furrow. It located between the Boumaâd Massif, lienne chain constitutes the substratum of this basin (Lepvrier, Beni Naceur Massif and Dahra in the north, and the Ouarsenis 1978, 1971), we distinguished an Early Neogene Tellian substra- strongholds south according to Perrodon (1957) and Mattaeur tum and a Neogene post-nappe basin.