The history and evaluation of saltwater intrusion into a coastal aquifer in Mersin, Turkey

doi:10.1016/j.jenvman.2003.12.007

Journal of Environmental Management

Volume 70, Issue 3, March 2004, Pages 275-282

https://doi.org/10.1016/j.jenvman.2003.12.007 Get rights and content

Abstract

The Mersin–Kazanlı region is a densely industrialized region. The factories and towns cover their water demand from groundwater. With the increased water demand, saltwater intrusion has occurred. The chloride concentration of the water samples from some wells has been analysed periodically since these wells were drilled. The results of these analyses and electrical conductivity measurements were used to show the history and development of saltwater intrusion up to the year 2000. The Cl⁻ concentration of the water within the alluvial aquifer increased to over 3000 mg/l in 1999 and the wells were closed completely. In 2001 new wells were drilled more than 1 km away from the sea and old well field. With the results of the analyses conducted in 2001, the current groundwater quality was determined. The ground water is of the magnesium–calcium-bicarbonate type and this composition is controlled by the interaction of the water with the sediments of alluvial deposits.

Introduction

The development of groundwater resources for water supply is a widespread practice in Turkey, favoured by the existence of basins with thick Quaternary deposits that form aquifers with good-quality water. Under steady-state conditions a state of equilibrium is established between seawater and freshwater in a coastal aquifer. However, owing to increasing demand for water, groundwater may be subjected to over-exploitation and the natural equilibrium is thus disturbed. This results in aggressive seawater intrusion, which may even reach the inland aquifer. The Mersin region is a dense industrialized region. There are many factories in this region, which cover their water demand from groundwater. Since the 1980's, with the economic development of the coastal areas of Mersin, salt-water intrusion has been induced by overexploitation of groundwater. In the mid 1990's, groundwater overexploitation exacerbated the salt-water intrusion, and the rate of intrusion continues to increase steadily. The salinization of the freshwater resources has seriously impeded the development of industry, agriculture and the improvement of the people's living standards in the region. The town of Kazanlı depends on the groundwater and today, because of the saltwater intrusion and pollution, the government plans to bring water from a dam which exists 25 km away from Kazanlı. This project is very expensive.

Monitoring of contaminated aquifers is an integral part of the activity related to the modern human–environment interaction and seawater intrusion is a typical result of such interaction (Melloul and Goldenberg, 1997).

A factory near Kazanlı has drilled 13 supply wells since the 1970's at different dates and analysed the chloride concentration and measured the electrical conductivity periodically. After they detected high chloride concentrations they stopped pumping from this well. As a result, seawater intrusion reached the inland aquifers. Only adequate seawater intrusion monitoring can lead to better management of such coastal aquifer. The purpose of this study is to describe the history and current condition of salinization in the Mersin–Kazanlı region and to show that the seawater intrusion can be detected and managed with a few parameters which are important in the composition of seawater chemistry.

Section snippets

Site description

Mersin is situated in the Mediterranean Sea region of Turkey. The study area is located between latitude 34° 37′ and 34° 57′ and longitude 36° 45′ and 37° 00′. The area is a delta plain, which is formed by Berdan River at the east and Deliçay creek at the west. The morphology in the study area is characterized by a wide flatness and it has an elevated altitude northwards. Topographic structure in the north of the investigated area has a wavy character. The altitude reaches to 300–1100 m in the

Geological setting

The basin is filled with Quaternary and Tertiary sediments (Fig. 1). These sediments are overlain Paleozoic metamorphic basement rocks, which crop out on the Taurus Mountain, along the northern border of the basin (Fig. 1). In the northwest of the study area ophiolitic rocks is settled. Tertiary sedimentary rocks consist of a succession of marine, lacustrine, and fluvial deposits.

The Middle-Upper Miocene aged Kuzgun formation consists of sandstone, conglomerate, limestone, tuff-marl-shale and

Hydrogeology

As the sandstone, conglomerate and limestone series of Kuzgun formation have karstik features they should form productive aquifers, but there are not any deep wells into these aquifers in the studied area. The conglomerate, sandstone and limestone are found mostly on the upper levels of Handere formation and form aquifers. There are some wells such as S-11, S-12 and S-13, which drain these series (Fig. 1). The recharge rate of Handere aquifer was estimated as 8.8×10⁶ m³/yr (Demirel and Türkmen,

Methodology

Saltwater can be detected directly in observation wells by electrical electrodes or by sampling, or indirectly by geoelectrical methods (Melloul and Goldenberg, 1997). In this study the direct method by sampling is used.

Water samples for chloride analysis were obtained every 15 days since the wells were drilled and at the same time the electrical conductivity was measured at the wellhead. The wells were drilled from 1974 at different dates. After some wells were affected by seawater such as

Results

The results of the analyses from the samples taken in 2001 are shown in Table 2. The groundwater is of the magnesium–calcium-bicarbonate type (Table 2, Fig. 2) and this composition is controlled by the interaction of the water with the sediments of alluvial deposits. In all samples, the chloride ion concentration is also very high. Dissolved chloride is common in shallow groundwater, but concentrations resulting from natural sources are generally low (Hem, 1992). Chloride concentrations in

Conclusions

Groundwater is an indispensable resource for water supply for the town Kazanlı, for the factories in Kazanlı field and for the agriculture. Between 1970 and 1980, under steady-state conditions a state of equilibrium was established between seawater and freshwater in this coastal aquifer. A factory in this region, which has 13 supply wells, overexploited the groundwater. As a result, the groundwater was polluted by seawater. The periodical chemical analysis and electrical conductivity

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