Qaraaoun Reservoir Research Articles

Groundwater Depletion Signals in the Beqaa Plain, Lebanon: Evidence from GRACE and Sentinel-1 Data

Regions with high productivity of agriculture, such as the Beqaa Plain, Lebanon, often rely on groundwater supplies for irrigation demand. Recent reports have indicated that groundwater consumption in this region has been unsustainable, and quantifying rates of groundwater depletion has remained a challenge. Here, we utilize 15 years of data (June 2002–April 2017) from the Gravity Recovery and Climate Experiment (GRACE) satellite mission to show Total Water Storage (TWS) changes in Lebanon’s Beqaa Plain. We then obtain complimentary information on various hydrologic cycle variables, such as soil moisture storage, snow water equivalent, and canopy water storage from the Global Land Data Assimilation System (GLDAS) model, and surface water data from the largest body of water in this region, the Qaraaoun Reservoir, to disentangle the TWS signal and calculate groundwater storage changes. After combining the information from the remaining hydrologic cycle variables, we determine that the majority of the losses in TWS are due to groundwater depletion in the Beqaa Plain. Results show that the rate of groundwater storage change in the West Beqaa is nearly +0.08 cm/year, in the Rashaya District is −0.01 cm/year, and in the Zahle District the level of depletion is roughly −1.10 cm/year. Results are confirmed using Sentinel-1 interferometric synthetic aperture radar (InSAR) data, which provide high-precision measurements of land subsidence changes caused by intense groundwater usage. Furthermore, data from local monitoring wells are utilized to further showcase the significant drop in groundwater level that is occurring through much of the region. For monitoring groundwater storage changes, our recommendation is to combine various data sources, and in areas where groundwater measurements are lacking, we especially recommend the use of data from remote sensing.

Influence of snow cover on water capacity in the Qaraaoun Reservoir, Lebanon

Considerable amount of surface water in Lebanon is stored behind dams, and the Qaraaoun Reservoir (QR) is a typical example. It is the largest surface water body in Lebanon where it irrigates 27,500 ha and generates 22% of Lebanon’s electricity. The reservoir is fed directly from the Litani River which receives water from several springs and from groundwater where both are replenished mainly from snowmelt. However, the relationship between snow cover area on the surrounding mountains and the water volume in the reservoir has not been investigated. This study aims at determining the influence of snow cover area as a water feeding source and the volume of water in the QR. The relationship between these two variables was calculated using satellite images (MODIS-Terra with 500 m spatial resolution) which enable retrieving measures each 8 days, and the in situ measuring instruments fixed in the QR. The investigated period was between 2001 and 2018. Results show that the water volume in the QR is substantially controlled by the snow cover area on the surrounding mountains. It was found that the average time period between snow accumulations on these mountains and the remarkable increase in water level in the QR is about 3 months, while the dynamic changes in snow cover (accumulation/melting) and the induced water level in the reservoir were calculated. In addition snow-water equivalent (SWE) was also determined. This study reveals the significance of snow cover, which either directly feeds the streams or indirectly replenishes the groundwater aquifers where both contribute in the water volume of the QR. Therefore, the catchment mountainous area where snow accumulates should be protected from human interventions which have been lately increased and impacted the hydrologic regime between snow cover and water volume in the QR.

Hydrodynamic influence on reservoir sustainability in semi-arid climate: A physicochemical and environmental isotopic study

Water scarcity and increasing water demand require the development of water management plans such as establishing artificial lakes and dams. Plans to meet water needs are faced by uprising challenges to improve water quality and to ensure the sustainability of hydro-projects. Environmental isotopes coupled to water physicochemical characteristics were investigated over a biennial cycle to assess both geomorphological and environmental impacts on the water quality of a reservoir situated in an intensively used agricultural watershed under a Mediterranean semi-arid climate. The particularity of the semi-arid climate and the diverse topography generate a continental and orographic rain effect on the isotopic composition of precipitation and the water recharged sources. The studied reservoir responds quickly to land-use activities and climatic changes as reflected by temporal and spatial variations of water chemistry and isotopic composition. Increasing changes in precipitation rate and dry periods significantly modified the water isotopic composition in the reservoir. During the first year, hydrogen (δD) and oxygen (δ18O) isotopes are depleted by 6 and 2‰ between dry and wet season, respectively. While a shift of −2‰ for δD and −1‰ for δ18O was detected during the second annual cycle. Environmental isotopic compositions demonstrate for the first time the occurrence of groundwater inflow to the central (Cz) and dam (Dz) zones of the Qaraaoun reservoir. The Cz and Dz can be considered as open water bodies subjected to dilution by groundwater inflow, which induces vertical mixing and reverse isotopic stratification of the water column. In the contrary, the river mouth zone acts as a closed system without groundwater intrusion, where heavy water accumulates and may act as a sink for contaminants during dry season. Groundwater influx acts as a dilution factor that renews the hypolimnion, and minimizes the perturbations induced by both internal biogeochemical reactions and external hydrological variations. Attention should be devoted to the hydrogeological location of planned reservoirs, which should take into account the vicinity of shallow water table to insure good water quality and water sustainability.

Metal binding in soil cores and sediments in the vicinity of a dammed agricultural and industrial watershed.

The environment is witnessing a downgrade caused by the amelioration of the industrial and agricultural sectors, namely, soil and sediment compartments. For those reasons, a comparative study was done between soil cores and sediments taken from two locations in the Qaraaoun reservoir, Lebanon. The soil cores were partitioned into several layers. Each layer was analyzed for several physicochemical parameters, such as functional groups, particle size distribution, ζ-potential, texture, pH, electric conductivity, total dissolved solids, organic matter, cation exchange capacity, active and total calcareous, available sodium and potassium, and metal content (cadmium, copper, and lead). The metal content of each site was linked to soil composition and characteristics. The two sites showed distinguishable characteristics for features such as organic matter, pH, mineral fraction, calcareous, and metal content. The samples taken toward the south site (Q1), though contain lower organic matter than the other but are more calcareous, showed higher metal content in comparison to the other site (Q2) (average metal content of Q1 > Q2; for Cd 3.8 > 1.8mg/kg, Cu 28.6 > 21.9mg/kg, Pb 26.7 > 19mg/kg). However, the metal content in this study did not correlate as much to the organic matter; rather, it was influenced by the location of the samples with respect to the dam, the reservoir's hydrodynamics, the calcareous nature of the soil, and the variation of the industrial and agricultural influence on each site.

Speciation of metals in bed sediments and water of Qaraaoun Reservoir, Lebanon

Determination of only total element in sediments does not give an accurate estimate of the likely environmental impacts. Speciation study of metals in sediment provides information on the potential availability of metals (toxic) to biota under various environmental conditions. In water, the toxic metal specie is the free hydrated metal ion. The toxicity of metals depends especially on their chemical forms rather than their total metal content. The present study focuses on Qaraaoun Reservoir, Lebanon. Earlier studies focused only on total metal concentrations in sediment and water. The objective of this study was to determine metal speciation (Fe, Cr, Ni, Zn, Cu, Pb, Cd) in the (operationally defined) sediment chemical fractions and metal speciation in reservoir water. This would reflect on metal bioavailability and toxicity. Water samples and bed sediments were collected from nine sites during the dry season and a sequential chemical fraction scheme was applied to the <75-μm sieve sediment fraction. Metal content in each fraction was determined by the FAAS technique. The data showed that the highest percentages of total metal content in sediment fractions were for: Fe in residual followed by reducible, Cr and Ni in residual and in reducible, Cu in organic followed by exchangeable, Zn in residual and in organic, Pb in organic and carbonate, Cd was mainly in carbonate. Total metal content in water was determined by ICP-MS technique and aqueous metal speciation was predicted using AQUACHEM software interfaced to PHREEQC geochemical computer model. The water speciation data predicted that a high percentage of Pb and Ni were present as carbonate complex species and low percentages as free hydrated ions, highest percentage of Zn as carbonate complex species followed by free hydrated ion, highest percentage of Cd as free hydrated ion followed by carbonate complex species. The sensitivity attempt of free hydrated ion of Ni, Zn, Pb, and Cd in reservoir water revealed dependence of Zn and Cd on pH and alkalinity, while Ni and Pb were only dependent on pH.

Variation of Metals in Bed Sediments of Qaraaoun Reservoir, Lebanon

The Qaraaoun Reservoir (impoundment of the River Litani) is the only artificial surface water body in the country, Lebanon. Earlier study on the water quality of the Qaraaoun Reservoir identified three water quality zoning with a central distinct zone suitable for multipurpose water usage. The objective of this study was to extend the earlier work by considering the total metal content of reservoir bed sediments and hence to evaluate factors that control metal deposition or capture. Water samples were collected from 15 sampling sites and sediment samples were simultaneously collected from 9 sites. Water parameters analyzed were pH, Eh, DO and temperature. Sediment samples were dried and sieved and sediment < 75 microm was retained for analysis. Sediments were subjected to a stepwise heating process with aqua regia to extract the metals, and their content in sediments determined by ICP-MS. The sediment data revealed higher metal contents where the river entered the reservoir which matched higher concentrations of water parameters at the influx site. Regression analysis of total metals in sediments with distance from the river Litani influx point to the dam revealed a log trend for Fe, Cr and Ni, whereas, the concentrations of Cu, Zn, Cd, Pb were better described by a polynomial regression. Three sediment zones were identified: entrance, oxidation (central) and reducing (near dam) zones. Sediment contents of Zn, Cu and Pb correlated with organic content, whereas sediment Cr and Ni were associated with iron. It was concluded that sediments act as a sink for metals and the deposition of metals is primarily related to sediment organic content and the level of dissolved oxygen in water.

Differential water quality in confined and free-flowing water bodies, Lebanon

Integrated management of water resources is a major critical issue to be addressed in combating water stress in developing countries, such as Lebanon. At present, surface water is not properly used in Lebanon. This emphasises the importance of assessing surface water quality as a projected means to increase water availability. This study involves two different water bodies, the freely flowing Nahr-Ibrahin River and the Qaraaoun Reservoir, an impoundment of the Litani River. Water samples were collected from 16 chosen sites of each water body at four different dates during the dry season. Measured water parameters were temperature, pH, conductivity, BOD, HCO3-, Ca2+, Mg2+, Cl-, SO42-, PO43-, NO3-, NH3, Fe, Mn, Zn, Pb, and Cd. Statistical analysis of the data revealed significant differences in water quality. The differences could be attributed to the fact that whereas the Qaraaoun reservoir is receiving domestic waste discharges that lead to an increase in the CO2 content and a pH decrease, the Nahr-Ibrahim River is influenced by agricultural runoffs and industrial discharges that increase the pH values. Consequently, the water metal speciation of the two water bodies was different. The study indicated that the differential quality of the two water bodies could be attributed to the nature of the water resources and exposure to contaminants. This is crucial in recommending intervention studies to protect quality and promote the role of surface water use, as an integrated component of water management in Lebanon.

Evaluation of water quality of the Qaraaoun Reservoir, Lebanon: suitability for multipurpose usage.

The increased demand on water resources in Lebanon as a result of: progressive urbanization, socio-economic growth, agricultural activities and development of industries is, according to the national authorities, a major critical factor by the year 2010. Political difficulties in earlier years imply a dearth of pertinent data. The objective of this study was to evaluate water quality of the Qaraaoun Reservoir of the Litani River and assess its feasibility for multi-purpose usage as one of the solutions to the aggravated water problems in Lebanon. Samples were collected from 18 sampling sites at several dates during the dry season. Parameters analysed were, pH, electrical conductivity, TDS, turbidity, alkalinity, Ca, Mg, TH, Cl-, SO4(2-), NH3, NO3(-), PO4(3-), Fe, Al, Na, Zn, Cr, Cu and As. The reported data were in compliance with WHO guidelines, USEPA regulation and EEC directives. Statistical analysis of the data defined three distinct environmental zones and water quality in the central, main zone satisfied most criteria. It is concluded that the reservoir water is fit for multipurpose uses, namely, drinking, domestic, recreational activities, irrigation, fisheries, livestock and industrial, and should be properly managed accordingly.

A prototype study for the management of surface water resources, Lebanon

Lebanon depends primarily, for its water resources on ground water that is deteriorating rapidly . The increased demand on water resources in Lebanon as a result of: progressive urbanization, socio-economic growth, development of agricultural and industrial activities will lead to critical water limitations factor by the year 2010. Consequently, other resources such as the availability of surface water in terms of quality and quantity is of major importance. The political instability in the country limited the development of a comprehensive data-base for surface water. The paper focuses on assessing the water quality of the Qaraaoun reservoir, an impoundment of the river Litani for multipurpose utilization. This would serve as a prototype for the development of comprehensive plans for optimal utilization of surface water sources in Lebanon, as a venue to meet the water needs of Lebanon. The Qaraaoun reservoir, which till now has limited utilization of hydroelectric power and agricultural activities, proved to posses other usage. A master plan for the management of the Qaraaoun reservoir, as a prototype for surface water, should address policy constrains relative to environmental, institutional and financial issues.