In Lebanese coastal regions, the uncontrolled exploitation of groundwater resources intended for domestic, industrial and agricultural purposes, imbalances the dynamic equilibrium between seawater and the flowing groundwater. Under such conditions, saltwater will intrude, which may have serious repercussions on both the prevailing environmental and economic conditions. In order to assess the status of salination of groundwater by seawater intrusion on the Lebanese coast, after the region of Choueifat – Rmeyle, situated in the south of Mount- Lebanon, the region going from Batroun to Akkar plain will be chosen as a study zone. In those regions, irrigation is mainly ensured by wells. Sampling will be done once a month. A complete physico-chemical analysis as well as Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) will be done. These analyses are meant to evaluate seawater intrusion and other forms of groundwater contamination, mainly by sewage water. Seawater intrusion will be assessed by using the chemical criteria and by studying, through a correlation analysis, the interrelations between the chemical and physical constituents of groundwater. In addition, climatic, pedological and geological data will be gathered to reveal the major causes of seawater intrusion. These data will also help to have the water balance in each region. Concrete solutions will be given including artificial recharge location and intensity.
Keywords: coastal aquifers, seawater intrusion, salinity, sound management, water balance, northern Lebanon.
I. INTRODUCTION
In Lebanon, more than 70% of the average yearly precipitation of 8,600 MCM is lost through different processes leaving 2,600 MCM of potentially available surface and groundwater resources with only 2,000 exploitable MCM (El Fadel, 2002). The total Lebanese water demands were evaluated at 2.500 MCM. Therefore, a clear water deficit is a threatening reality aggravated by increased demands and changing land use. In fact, any reduction in the plant cover associated with a high rate of urbanization (Masri et al., 2002, Darwish et al., 2003), in particular along the coastal regions, would have severe consequences on the total water balance, by a rise in the surface runoff at the expense of the vertical infiltration into the ground water. All this has contributed to the elaboration of the Lebanese water shortage issue. As a result of the population growth, the industrial development, the expansion of irrigated agricultural land and mainly because of the ever-increasing chaotic exploitation of groundwater resources, the use of available water resources is reaching unsustainable levels.
Of all economic sectors requiring water, agriculture is the major consumer as the water withdrawal intended for irrigation was estimated at 68% of the total amount withdrawn. Of these, surface water sources represent 54.3% and the groundwater such as artesian wells, recharge wells and springs 45.7% (FAO, 1996). Due to the government reluctance in the implementation of large-scale irrigation schemes, the amount of groundwater intended for irrigation has seriously increased in the past few years. Individual farmers are increasingly relying on water supply from groundwater resources by means of private wells. Around 2000 wells were added, during 1992-1995, to a total exceeding the 10,000 wells especially in the central Bekaa plain as well as in the Southern and Northern hills (FAO, 1996).
In coastal regions, the uncontrolled exploitation of groundwater resources intended for domestic, industrial and agricultural purposes, imbalances the dynamic equilibrium between seawater and the flowing groundwater, favoring the saltwater intrusion. Under such conditions, saltwater penetration may cause serious repercussions on both the prevailing environmental and economic conditions.
The coastal area of Choueifat-Rmeyle region is one of many districts in Lebanon, threatened by the penetration of seawater into the aquifers (El Moujabber and Bou Samra, 2002; El Moujabber et al., 2004). Due to the absence of collective irrigation networks in this pilot area, irrigation is mainly secured by private wells. This area is a typical horticultural region, mainly involved in greenhouse production of strawberries, cucumbers and tomatoes.
Despite the importance of the ever-increasing salination issue in that region, not enough data is made available for assessing the groundwater quality. The degradation in water quality could have detrimental effects on the agricultural production (FAO, 1985). Therefore, it is very important to quantify salinity increments and its impact on crop production. Moreover, the agricultural practices could also, in their turn, contribute to the deterioration of the water quality. In these intensive production systems, excessive fertilizer utilization and high evaporation could lead to significant salts build-up in the soil (Atallah et al., 1997 and 2000;) and to some extent to structure deterioration due to high sodium content (El Moujabber et al., 2004).
With prevailing needs for water allocated for irrigation, the seasonal disparity between the period of precipitation (winter) and the time of maximum demand for irrigation water (dry summer) has consistently led to excessive and uncontrolled withdrawal of groundwater. Such patterns have led to severe lowering of water table and ultimately caused saltwater intrusion along the coast. Water quality is as important as its quantity since its quality greatly affects the type of use and vice-versa. In the mountainous Lebanese rural areas where this water is later used for irrigation or as a source of drinking water, serious health problems due to bacterial contamination of rivers, springs and groundwater are current (Jurdi, 1995). In coastal areas, saltwater intrusion poses a serious threat to the quality of freshwater, particularly that in some locations seawater has actually intruded several kilometers inland into coastal aquifers (El Moujabber and Bou Samra, 2002). Other agricultural practices have also contributed to a diminishing water quality. Excessive fertilizer utilization in some areas has led to nitrate leaching which has been detected in elevated concentrations in groundwaters (Moeller et al., 2003). In addition, the unregulated application of pesticides and the discharge of raw sewage into surface and ground waters may cause the contamination of surface and subterranean waters, particularly in shallow aquifers.
The uncontrolled disposal of solid wastes in watersheds has also led to the contamination of river basins due to the leaching of chemicals. While these wastes will likely contaminate surface waters in the area, they might also infiltrate through fissured bedrock and pollute the groundwater downstream of dumpsite, thus expanding the contaminated region.
In contrast to the seawater movement inland, the Lebanese marine springs were geophysically investigated by a thermal infrared methodology. The survey was conducted by the FAO in 1973 and thermal anomalies were plotted on maps. Yet, the total discharge of these springs has yet to be known. Expectedly, their discharge varies from season to season and from year to year; similarly to land springs. Maximum discharges occur during August and September. Usually, marine springs are hard to track unless their discharges exceed the 15 l/s or 0.015m3/s (Davis and Deweist, 1966). The anomalies were detected by thermal infrared imagery three decades later and revealed 30% decrease in their number (CNRS, 2002). By plotting the marine springs on the hydrogeologic map of the area, it can be noted that the anomalies in at least three locations are associated with faults. So there is a possibility here that the groundwater flow is associated with the fault system promoting a direct contact of seawater with the coastal aquifer
2. Objectives
The objectives of this study are:
3. Materials and methods
The number of wells to be tested will be around 20 distributed among the regions: Batroun and Akkar.
GPS will be used to determine the geographical position of each well. Piezometric levels and complete physical and chemical analysis will be done once a month. In addition BOD, COD will be established.
Several maps will be produced to calculate water balance and determine pedological and geological conditions in each region.
As for outputs and activities, they can be summarized as follows:
Output 1 Seawater intrusion
Activity 1 Sampling
Activity 2 Analysis
Activity 3 Assessment
Output 2 Water balance and maps production
Activity 1 Maps production
Activity 2 Watersheds delimitation
Activity 3 Water balance calculation
Output 3 Seawater intrusion remediation
Activity 1 Analysis
Activity 2 Calculation
Activity 3 Assessment
4. Importance of the subject
This study complements previous studies but in different regions
5. References
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Atallah, T., Darwish, T. and El Moujabber, M., 1997. Cultural practices and soil salinity in greenhouses in Lebanon. In: International Conference on: Water management, salinity and pollution towards sustainable irrigation in the Mediterranean Region. Bari-Italy, 22-26 September. 115-123.
CNRS/NCRS, GORS. 2002. Hydrogeological assessment of water resources in the Lebanese coastal region: utilization of Remote Sensing. National Center for Remote Sensing (Lebanon) and General Organization for Remote Sensing (Syria). Symposium on the Final Report, Beirut, 56p.
Davis, S. and Deweist, A., 1966. Hydrogeology. John Willey and Sons, Inc., New York, 463p.
El Fadel, M. 2002. Water resources in Lebanon current situation and future needs. Workshop on water resources in Lebanon. Lebanese parliament/UNDP 13-02-2002.
El Moujabber, M. and Bou Samra, B., 2002. Assessment of groundwater salination by seawater intrusion in a typical Lebanese horticultural area. Acta Horticulturae 573:195-202.
El Moujabber, M., Atallah, T., Darwish, T. and Bou Samra, B, 2004. Monitoring of groundwater salination by seawater intrusion on the Lebanese Coast. Lebanese Science Journal, 5:2, 21-36
FAO, 1985. La qualité de l'eau agriculture. Bull. FAO Irrig. Drainage, 29.
FAO, 1996. Irrigation in the Near East Region in figures. Water Reports, p. 135-143.
Jurdi M., 1995. Potable water in Lebanon: Quality and quantity control program. Environmental Management for sustainable development in Lebanon. First National Meeting. Beirut 31 March-01 April 1995: 225-233.
Masri, T., Khawlie, M., and Faour, G. 2002. Land cover change over the last 40 years in Lebanon. Lebanese Science Journal, 3 (2): 17-28.
Moeller A. Altfelder S. Moeller H. W. Darwish T. and G. Abdelgawad (2003). A guide to sustainable nitrogen management in agricultural practices. Volume 8. ACSAD, BGR and CNRS/L. 90 p.