Evaluating the anthropogenic and geologic impacts on water quality of the Eğirdir Lake, Turkey

E?irdir Lake is the second largest fresh water lake with 482 km² surface area of Turkey. The lake is an indispensable water source for our country and region because of available water capacity and usage aims such as drinking-irrigation water, tourism, and fishing. However, especially contaminants located in the E?irdir Lake catchment affect the lake water quality negatively in times. Therefore, determination of the water quality of the lake has quite importance for region human health and sustainable usage of the lake. The major factors that control the quality of the E?irdir Lake water are agricultural activities in the basin, water–rock interaction, and domestic and industrial wastes. This study investigates the anthropogenic and geologic impact originated from pollution sources and water–rock interaction in the lake watershed basin to the E?irdir Lake water quality. For this purpose, geological, hydrogeological, and hydrological properties of the lake basin with point and nonpoint pollution sources were investigated. To determine the water quality of the lake, 48 water samples were collected especially from locations representing effects of pollutants in May and October 2009. The analysis results were compared with maximum permissible limit values recommended by World Health Organization and Turkish drinking water standards. The contents of all chemical and physical parameters are higher in dry periods than wet period, and water pollution was observed at discharge points of the streams into the lake. Also, pH, turbidity, potassium, chemical oxygen demand, ammonium, aluminum, iron, and lead concentrations were found to be above drinking water standards.     

Comparative discharges of fresh and waste water along the California coast

As the population of California grows, the discharge of domestic and industrial waste water and power-plant cooling water into coastal waters continuously increases. About 0.75 × 10⁶ m³ of industrial waste water, 3.75 × 10⁶ m³ of domestic waste water, and 26.5 × 10⁶ m³ of thermal effluent are discharged daily into California's nearshore waters. These waters do not have an infinite capacity to break down and disperse the pollutants. Waste water discharged near shore may remain there for considerable time and have a significant effect on water quality and marine life. The low population and wet climate of the northern coastal region have led to small discharges of waste water but very large inputs of fresh water to the ocean. Southward along the Pacific Coast the climate becomes more arid, and population increases. This combination leads to a large excess of waste-water over fresh-water discharge. Many individual waste-water discharges exceed the average daily discharge of most of the rivers which enter the coastal waters.     

The hydrogeochemistry of the Lake Waco drainage basin,Texas

The origin of surface water chemistry in highly impacted drainage basins must be investigated on a drainage-basin scale if the causes of the pollution are to be elucidated. This study characterizes and deciphers the surface water chemistry of a nutrient polluted river system in central Texas. Four tributaries of the Lake Waco reservoir were chemically characterized temporally and spatially in order to gain a complete understanding of the nature and origin of dissolved solids being transported into the lake. Temporal chemical variations measured at the base of each of the drainage basins are repetitive and seasonal. The most periodic and well-defined variation is exhibited by nitrate concentrations although many of the other solutes show seasonal changes as well. These temporal chemical changes are controlled by seasonal precipitation. During rainy seasons, the shallow aquifer is recharged resulting in stream discharge that is high in nitrate, calcium, and bicarbonate. When the shallow flow system is depleted in the summer, stream waters are dominated by deeper groundwater and become rich in sodium. Spatial variations in the chemistry of South Bosque surface waters were characterized using the snapshot technique. The spatial distribution of nitrate in surface waters is controlled by fertilizer application to row crops and the location of a munitions factory. The concentrations of naturally derived solutes such as Ca⁺, Na⁺, Cl^–, and SO₄^–2are controlled by underlying lithologies.     

Estimating groundwater inflow and leakage outflow for an intermontane lake with a structurally complex geology: Georgetown Lake in Montana,USA

Stable isotopes of the water molecule (δ¹⁸O and δD) for groundwater, lake water, streams, and precipitation were coupled with physical flux measurements to investigate groundwater–lake interactions and to establish a water balance for a structurally complex lake. Georgetown Lake, a shallow high-latitude high-elevation lake, is located in southwestern Montana, USA. The lake is situated between two mountain ranges with highlands primarily to the east and south of the lake and a lower valley to the west. An annual water balance and (δ¹⁸O and δD) isotope balance were used to quantify annual groundwater inflows of 2.5?×?10⁷ m³/year and lake leakage outflows of 1.6?×?10⁷ m³/year. Roughly, 57% of total inflow to the lake is from groundwater, and 37% of total outflow at Georgetown Lake is groundwater. Stable isotopes of groundwater and springs around the lake and surrounding region show that the east side of the lake contains meteoric water recharged annually from higher mountain sources, and groundwater discharge to the lake occurs through this region. However, springs located in the lower western valley and some of the surrounding domestic wells west of the lake show isotopic enrichment indicative of strong to moderate evaporation similar to Georgetown Lake water. This indicates that some outflowing lake water recharges groundwater through the underlying west-dipping bedrock in the region.     

Mobilization of gold into lake sediments from acid and alkaline mineralized environments in the southern Canadian Shield: Gold in lake sediments and natural waters

To be an effective indicator of mineralization in lake sediment surveys within the Canadian Shield, it is desirable that an element migrate in solution or adsorbed on suspensates. Given the low relief and disorganized drainage patterns of this region, dispersal in clastic form in drainage systems is limited and gives rise to erratic distributions. The purpose of this study was to discover whether Au shows significant hydromorphic mobility, which would justify the increasing use that is being made of this element in lake sediments as an indicator for gold mineralization.Waters and lake sediments were collected from Napier Lake, Ontario; PAP Lake, Saskatchewan; and Foster Lake, Manitoba, all of which contain Au-quartz vein mineralization and lie within the glaciated boreal forest zone of the Canadian Shield. In all three areas, profundal lake sediments down-drainage of mineralization contain Au concentrations higher than regional mean concentrations. Significant dissolution and transport of Au was found under oxidizing conditions associated with waters with pH that varied from acid to alkaline. Waters from drill holes penetrating mineralization contain up to 401 ng L⁻¹ Au (note; 1 ng L⁻¹ is equivalent to 1 part per trillion, 10⁻¹²). Surface waters overlying or near mineralization collected from bogs, seeps, ponds and streams contain up to 13 ng L⁻¹. The content of Au in lake waters is lower, with a maximum of 1.1 ng L⁻¹. There is also a detectable quantity of Au present in suspensates. Two samples of particulates (> 1 μm) filtered from lake water have Au equivalent to 0.17 ng L⁻¹ and 0.039 ng L⁻¹. While the contents of Au present in solution or as suspensates in lake and stream water are relatively small, they are sufficient, if precipitated, to generate anomalies in lake sediments. Thus for Reservoir Lake, in the Foster Lake area, water from the principal stream entering the lake carries 0.3 ng L⁻¹ Au. This provides an annual flux which far exceeds that required to generate the 7.3 ppb Au contained in profundal sediments of this lake; a content that is anomalous relative to the regional median content of < 1 ppb Au for lake sediments.Hydrogeochemical prospecting involving analysis for Au is one method for tracing the source of anomalous Au in lake sediments. Collection of 1 L samples without field treatment, followed by extraction of Au into MIBK, then analysis by graphite-furnace atomic absorption spectrophotometry, permits detection levels for Au of 0.5 ng L⁻¹. This is below the contents of Au found in some waters from mineralized areas. A detection limit of 0.3 ng L⁻¹ was obtained using larger water samples.     

Use of dissolved chloride concentrations in tributary streams to support geospatial estimates of Cl contamination potential near Skiatook Lake,northeastern Oklahoma

Releases of NaCl-rich (>100 000 mg/L) water that is co-produced from petroleum wells can adversely affect the quality of ground and surface waters. To evaluate produced water impacts on lakes, rivers and streams, an assessment of the contamination potential must be attainable using reliable and cost-effective methods. This study examines the feasibility of using geographic information system (GIS) analysis to assess the contamination potential of Cl to Skiatook Lake in the Hominy Creek drainage basin in northeastern Oklahoma. GIS-based predictions of affects of Cl within individual subdrainages are supported by measurements of Cl concentration and discharge in 19 tributaries to Skiatook Lake. Dissolved Cl concentrations measured in October, 2004 provide a snapshot of conditions assumed to be reasonably representative of typical inputs to the lake. Chloride concentrations ranged from 5.8 to 2300 mg/L and compare to a value of 34 mg/L in the lake. At the time of sampling, Hominy Creek provided 63% of the surface water entering the lake and 80% of the Cl load. The Cl load from the other tributaries is relatively small (<600 kg/day) compared to Hominy Creek (11 900 kg/day) because their discharges are relatively small (<0.44 m³/s) relative to Hominy Creek (3.1 m³/s). Examination of chemical components other than Cl in stream and lake waters indicates that many species, such as SO₄, cannot be used to assess contamination potential because they participate in a number of common biogeochemical processes that alter their concentrations.     

西藏阿里地区泽错大型盐湖锂（硼）矿床的发现及开发利用前景

2016—2018年中国地质调查局天津地质调查中心联合西藏自治区地质矿产勘查开发局第五地质大队组建盐湖调查队伍,针对西藏羌塘盆地西段泽错盐湖开展调查评价工作,探获大型锂(硼)矿产地1处。泽错湖表水体长16.3 km,宽3.3～11.3 km,湖表面积113.8 km2。湖水深度变化较大,四周水较浅,逐渐向中间变深,最深处达44 m,湖水平均深度为24 m,湖面海拔4940 m。泽错盐湖位于藏北羌塘—三江复合板块内,矿区第四纪地层可划分为更新统湖积,全新统现代湖水,全新统冲洪积,全新统冲积和全新统湖积。湖盆可划分基岩裂隙水层、亚砂土孔隙含水层、亚黏土孔隙含水层和湖表卤水4个水文地质单元。经计算直接补充到湖盆表面的大气降水量为1.081×107m3/a,地表水补给湖水量为8.262×107m3/a,地下水补给量为2.052×107m3/a,泽错年补给水量为11.395×107m3/a左右。自然蒸发为泽错湖盆的主要排泄方式,泽错湖水年蒸发量为12.745×107m3/a,年均水量变化值为1.35×107m3/a,地表水补给湖水带入的总盐量为7.8×104t/a。泽错湖盆卤水中主要成盐元素有Cl-、Na+、SO42-、K+、CO32-、HCO3-、B2O3、Mg2+、Li+等,平均矿化度41.57 g/L,pH值为9.31,泽错湖水为高矿化度盐水,水化学类型为硫酸钠亚型。泽错盐湖LiCl平均品位为376.02 mg/L,LiCl资源量为102.68×104t,远景规模达到大型;B2O3平均品位为840 mg/L,B2O3资源量为229.38×104t,远景规模达到大型。在综合分析锂、硼资源需求、提锂技术、盐田建设、气候条件、经济价值等方面的基础上,对泽错盐湖的开发利用前景进行了展望。     

Seepage measurements from Long Lake,Indiana Dunes National Lakeshore

 Long Lake, located near Lake Michigan within the dune-complexes of Indiana Dunes National Lakeshore, USA, was formed some time during the Pleistocene and Holocene epochs. A surficial aquifer underlies Long Lake, which is either a source or sink for the later. The hydrologic processes in the lakeshore and surrounding environs have been significantly altered during the agricultural, municipal, and industrial development of the region. Limited data suggest that the organisms of Long Lake have elevated levels of several contaminants. This study attempts to quantify seepage within the lake to assess the potential threat to groundwater quality. Seepage measurements and minipiezometric tests were used to determine seepage within the lake. Seepage measurements and minipiezometric tests suggest that water seeps out of Long Lake, thus recharging the groundwater that flows southwest away from the lake. There is a great deal of variability in the seepage rate, with a mean of 11.5×10^–4±11.2×10^–4 m d^–1. The mean seepage rate of 0.3 m yr^–1 for Long Lake is greater than the 0.2 m yr^–1 recharge rate estimated for the drainage basin area. The Long Lake recharge volume of 2.5×10⁵ m³ yr^–1 is approximately 22% of the volume of the lake and is significant when compared to the total surface recharge volume of 4.8×10⁵ m³ yr^–1 to the upper aquifer of the drainage area. There is a potential for contamination of the groundwater system through seepage from the lake from contaminants derived from aerial depositions. Received: 16 August 1995 · Accepted: 18 September 1995     

太湖流域营养盐产量演变和趋势的数值模拟研究

认识流域湖泊水体富营养化的演变和趋势是湖泊污染控制和治理中的重要研究课题。本文将在分析和论证太湖流域营养盐自然本底、人类活动作用急剧增加的近50年来太湖流域营养盐的变化情况、以及全球气候变化和流域经济发展未来30年太湖流域营养盐变化趋势等三方面的基础上,对太湖流域营养盐产量变化做出评估和预测。研究表明,在未来气候变化概率分析和区域经济发展规划基础上,太湖流域未来30年营养盐流域产量将比现代（2000s）增加25%～33%,这将增大太湖水体污染的压力。     

Elemental and isotopic geochemistry in the hydrothermal area of Chaves,Vila Pouca de Aguiar (northern Portugal)

Chaves thermal waters (76°C) are the most important external manifestations of low-temperature geothermal systems occurring in Portuguese mainland. They are related to crystalline granitic rocks. This paper describes the use of the environmental isotopic composition (oxygen-18, deuterium, and tritium) of hot and cold waters of the Chaves area as an important hydrogeological tool to solve specific problems arising in the appraisal of the geothermal resources of the area (e.g., origin and age of waters, recharge area, and underground flow paths).¹⁸O and D analyses seem to confirm the meteoric origin of Chaves thermal waters. The local altitude dependence of meteoric waters was determined by¹⁸O and D analyses of superficial and shallow groundwaters of the Chaves plain and its bordering mountains. Chaves thermal waters seem to be related to meteoric waters, infiltrated on the highest topography areas (Bolideira granitic outcrop NE Chaves), that percolate at great depth and emerge in a discharge area at lower altitude (Chaves plain). Chaves thermal waters showing little oxygen-18 shift and low tritium concentrations could be considered external manifestations of an old geothermal system in which the isotopic water-rock interaction is adjusted to equilibrium.     

Quantification of the water balance and hydrogeological processes of groundwater–lake interactions in the Pampa Plain, Argentina

This paper gives an account of the assessment and quantification of the water balance and the hydrogeological processes related to lake–groundwater interaction in the Pampa Plain by using hydrogeochemical, isotopic and flow numerical modeling techniques. La Salada is a permanent shallow lake, with an area of 5.8 km², located on the SE of Buenos Aires Province. A total of 29 lake water samples and 15 groundwater samples were collected for both hydrochemical analysis and environmental stable isotope determination. Water table depths were measured in wells closed to the lake. Groundwater samples appear grouped on the Local Meteoric Water Line, suggesting a well-mixed system and that rainfall is the main recharge source to the aquifer. Water evaporation process within La Salada is also corroborated by its isotopic composition. The model that best adjusts to La Salada Lake hydrochemical processes includes evaporation from groundwater, calcite precipitation with CO₂ release and cationic exchange. The annual water balance terms for the lake basin indicates for each hydrological component the following values: 1.16 E⁰⁸ m³ rainfall, 8.15 E⁰⁷ m³ evapotranspiration, 1.90 E⁰⁶ m³ runoff, 1.55 E⁰⁷ m³ groundwater recharge, 6.01 E⁰⁶ m³ groundwater discharge to the lake, 9.54 E⁰⁶ m³ groundwater discharge to the river, 5.00 E⁰⁵ m³ urban extraction and 4.90 E⁰⁶ m³ lake evaporation. Integrated analysis of hydrochemical and isotopic information helped to calibrate the groundwater flow model, to validate the conceptual model and to quantitatively assess the basin water balance.     

Assessment of groundwater vulnerability based on a modified DRASTIC model, GIS and an analytic hierarchy process (AHP) method: the case of Egirdir Lake basin (Isparta, Turkey)

A DRASTIC-model method based on a geographic information system (GIS) was used to study groundwater vulnerability in Egirdir Lake basin (Isparta, Turkey), an alluvial area that has suffered agricultural pollution. ‘Lineament’ and ‘land use’ were added to the DRASTIC parameters, and an analytic hierarchy process (AHP) method determined the rating coefficients of each parameter. The effect of lineament and land-use parameters on the resulting vulnerability maps was determined with a single-parameter sensitivity analysis. Of the DRASTIC parameters, land use affects the aquifer vulnerability map most and lineament affects it least, after topography. A simple linear regression analysis assessed the statistical relation between groundwater nitrate concentration and the aquifer vulnerability areas; the highest R ² value was obtained with the modified-DRASTIC-AHP method. The DRASTIC vulnerability map shows that only the shoreline of Egirdir Lake and the alluvium units have high contamination potential. In this respect, the modified DRASTIC vulnerability map is quite similar. According to the modified-DRASTIC-AHP method, the lakeshore areas of Senirkent-Uluborlu and Hoyran plains, and all of the Yalvaç-Gelendost plain, have high contamination potential. Analyses confirm that groundwater nitrate content is high in these areas. By comparison, the modified-DRASTIC-AHP method has provided more valid results.     

Heavy metal abundances in the Kandy lake—An environmental case study from Sri Lanka

The Kandy lake, situated in the heart of Sri Lanka's second largest city with a population of nearly 120,000, has been monitored to probe the extent of heavy metal pollution. Although the lake is a source of drinking water to the city, a large number of effluent canals drain into the lake carrying a continuous flow of industrial and domestic waste matter. A total of 66 surface water samples were analyzed for their Fe²⁺, total Fe, total V, SO ₄ ²⁻ , Cd²⁺, and Pb²⁺ contents. Pb and Cd were found in high concentrations averaging 150 μg/l and 77 μg/l, respectively, and exhibit a marked positive correlation with each other (r=+0.94). Vehicular emissions and industrial waste matter contribute largely to the Pb and Cd contents of the lake, the anthropogenic influence outweighing the contributions made by geological materials. All field observations and laboratory experiments indicate a tendency of the Kandy Lake towards eutrophicity.     

Quantification of groundwater discharge into lakes using radon-222 as naturally occurring tracer

A case study was carried out with the aim to practically test whether estimates of groundwater discharge rates into dredging lakes can be made via an uncomplicated and straightforward technique using radon-222 as naturally-occurring groundwater tracer. Lake Ammelshainer See, a dredging, seepage lake, approximately 25 km east of Leipzig, Germany, was chosen as the investigation site. In order to evaluate changes in the spatial and temporal radon-222 patterns in the lake during different stages of stratification, sampling campaigns were conducted in April 2007 (well mixed stage) and in May 2007 (thermal stratification stage). Groundwater flow estimates were made using a radon mass balance approach accounting for all radon fluxes into and out of the lake and assuming steady-state conditions with respect to these radon fluxes. Once all positive and negative radon fluxes related to the lake water volume were determined, groundwater discharge was estimated by using the advective radon input and the radon activity concentration of the pore water as key parameters. The results showed that in case of a lake with a size and shape of Lake Ammelshainer See (530,000 m²) reasonable groundwater discharge estimates can be made by collection and analyzing just a few water samples and a few samples from the sediment layer.     

Constraints on water chemistry by chemical weathering in the Lake Qinghai catchment, northeastern Tibetan Plateau (China): clues from Sr and its isotopic geochemistry

Lake water, river water, and groundwater from the Lake Qinghai catchment in the northeastern Tibetan Plateau, China have been analyzed and the results demonstrate that the chemical components and ⁸⁷Sr/⁸⁶Sr ratios of the waters are strictly constrained by the age and rock types of the tributaries, especially for groundwater. Dissolved ions in the Lake Qinghai catchment are derived from carbonate weathering and part from silicate sources. The chemistry of Buha River water, the largest tributary within the catchment, underlain by the late Paleozoic marine limestone and sandstones, constrains carbonate-dominated compositions of the lake water, being buffered by the waters from the other tributaries and probably by groundwater. The variation of ⁸⁷Sr/⁸⁶Sr ratios with cation concentrations places constraint on the Sr-isotopic compositions of the main subcatchments surrounding Lake Qinghai. The relative significance of river-water sources from different tributaries (possibly groundwater as well) in controlling the Sr distribution in Lake Qinghai provides the potential to link the influence of hydrological processes to past biological and physical parameters in the lake. The potential role of groundwater input in the water budget and chemistry of the lake emphasizes the need to further understand hydrogeological processes within the Lake Qinghai system.     

Contributions of boron isotopes to understanding the hydrogeochemistry of the coastal detritic aquifer of Castellón Plain,Spain

The Castellón Plain alluvial aquifer, Spain, is intensively exploited to meet the demand for agricultural irrigation and industrial water supply. The geochemistry of its groundwater shows complex salinization in the northern and southern parts of the aquifer, with significant pollution from human origin in the central portion. Boron content and B isotope geochemistry are useful for distinguishing between various sources of pollution and their relative importance in different parts of this aquifer. Boron concentrations in the groundwater vary between 0.01 and 0.85 mg/L. In the more saline groundwaters, found at the northern and southern ends of the study area, the presence of B is linked to inputs from seawater and water with a calcium-magnesium sulphate facies, which feed the aquifer and clearly influence the chemistry of its waters. Evidence of B adsorption processes in some samples is shown by the low B/Cl ratios and the high values of δ¹¹B. In the central portion of the aquifer, the high B/Cl ratios and the strongly negative δ¹¹B are related to pollution of human origin.     

Groundwater sustainability and groundwater/surface-water interaction in arid Dunhuang Basin,northwest China

The Dunhuang Basin, a typical inland basin in northwestern China, suffers a net loss of groundwater and the occasional disappearance of the Crescent Lake. Within this region, the groundwater/surface-water interactions are important for the sustainability of the groundwater resources. A three-dimensional transient groundwater flow model was established and calibrated using MODFLOW 2000, which was used to predict changes to these interactions once a water diversion project is completed. The simulated results indicate that introducing water from outside of the basin into the Shule and Danghe rivers could reverse the negative groundwater balance in the Basin. River-water/groundwater interactions control the groundwater hydrology, where river leakage to the groundwater in the Basin will increase from 3,114?×?10⁴ m³/year in 2017 to 11,875?×?10⁴ m³/year in 2021, and to 17,039?×?10⁴ m³/year in 2036. In comparison, groundwater discharge to the rivers will decrease from 3277?×?10⁴ m³/year in 2017 to 1857?×?10⁴ m³/year in 2021, and to 510?×?10⁴ m³/year by 2036; thus, the hydrology will switch from groundwater discharge to groundwater recharge after implementing the water diversion project. The simulation indicates that the increased net river infiltration due to the water diversion project will raise the water table and then effectively increasing the water level of the Crescent Lake, as the lake level is contiguous with the water table. However, the regional phreatic evaporation will be enhanced, which may intensify soil salinization in the Dunhuang Basin. These results can guide the water allocation scheme for the water diversion project to alleviate groundwater depletion and mitigate geo-environmental problem.     

Chemometric approach integrated with capillary electrophoresis for the investigation of public water system sources and quality

A chemometric approach coupled with capillary electrophoresis based on the hierarchical cluster analysis and principal component analysis has been applied for the investigation of the water quality in the Golcuk-Isparta region (Lake District of Turkey). In the research area, Egirdir Lake, Golcuk Lake and surrounding ground and domestic waters have been utilized as drinking water resources. Golcuk Lake is distinctive in terms of high fluoride content (3.50 ± 0.21 mg/mL) which is endemic in volcanic areas where the water flow through volcanic rocks and sediments. Based on the analysis of major anions chloride, sulfate, nitrate and fluoride with capillary electrophoresis, twenty-four drinking water sampling sites in the research area were classified into four classes using the hierarchical cluster and principal component analysis. Combining the research area investigation results of hierarchical cluster and principal component analysis, it was found that fluoride concentration is the major diagnostic variable to determine the quality of drinking waters, and all the other anions are the important classification factors to predict the resources of the drinking water samples, individually. To sum up, this study reveals the potential of the use of capillary electrophoresis in combination with chemometric techniques for the determination of the quality and origin of drinking waters.     

Assessment of variations in water quality using statistical techniques: a case study of Işıklı Lake, Çivril/Denizli,Turkey

A study of the hydrochemical evaluation of waters in the I??kl? Lake and surrounding area was carried out with the objective of identifying the geochemical processes and their relation with water quality in the region. The multivariate statistical techniques were used in the hydrochemical evaluation of waters. Statistical analysis of water quality parameters was made to seeing the interrelationship between different variables in order to explain the water quality and pollution status of study area. For this purpose, water samples were taken from lake, river, stream, and springs which are represented by investigated area and water qualities were evaluated. Generally, Ca²⁺, Mg²⁺, and Cl^?, HCO₃ ^? ions are dominant within surface water and water sources. Arsenic concentration increase is determined in I??kl? spring and Kufi stream water samples. Also, aluminum concentration is high level in the Kufi stream water samples. This increase was related to igneous rocks as geogenic origin. Also, geogenic contamination was identified in R-mode factor and cluster analyses. There is high correlation between electrical conductivity and major ions of waters.     

Threat of glacial lake outburst flood to Tehsil Gupis from Khukush Lake, District Ghizer, Gilgit Baltistan, Pakistan

Glacial lake outburst flood (GLOF) is a powerful natural phenomenon that is very active in the Karakoram and Himalayas. This paper presents a case study from Gupis Tehsil in northern areas of Pakistan that is exposed to GLOFs from nine different glacial lakes in its upper catchment areas. Khukush Lake being the largest of all the glacial lakes has been studied and a flood attenuation model has been created for the whole Gupis Tehsil. This lake covers almost 2.2 km² of surface area, and its calculated volume is 2.6 × 10⁴ m³. In case of its outburst, the peak flow discharge is calculated to be 7,642 m³/s. The catchment area which contributes water and debris to the lake is 170 km². This lake is dammed by a glacial moraine, which is not strong enough to sustain the pressure for a longer period of time. Other factors that are reducing the reliability of the dam are the secondary hazards which are in direct contact with the lake, and in case of their reactivation, they can put severe impacts on the dam. There are eight potential sites of the snow avalanche activity where debris along with snow may fall directly into the lake producing a strong wave. This strong wave of water will increase the pressure on the dam and ultimately will increase the probability for its outburst. The presense of water springs towards the downstream side of the natural dam also indicate the presence of hidden channels passing through the dam which may weaken the shear strength of the dam. Almost 24 villages settled along either sides of the Gupis River are critically studied for the expected flood from Khukush Lake. With few exceptions, almost 20–25 % area of all the villages will be affected from this flood.