Domestic Water Supply Research Articles

Seasonal Change of Physicochemical Properties of Kayalıköy Reservoir (Kıklareli/Turkey) and Determination of Water Quality

This study was carried out in the Kayalıköy reservoir (Kırklareli, Turkey), that is used for agricultural irrigation and aquaculture and to provide drinking and domestic water supply of Edirne province. The study was performed at 3 stations determined in the reservoir during a year from May 2018 to April 2019. The water samples were taken with Ruttner water sample bottles from 15 to 20 cm below the water surface. Water temperature, Secchi disk depth, conductivity, pH, and dissolved oxygen were measured on-site simultaneously with the sampling time. Other physicochemical parameters were analyzed in the laboratory. A total of 43 physicochemical parameters were measured in the Kayalıköy reservoir. Analysis results obtained are compared with Regulation on Modification of Surface Water Quality Management (RSWQM) and Regulation on the Quality and Treatment of Water Provided for Drinking Water (RDWQ). According to the average values of the analysis results the water quality in Kayalıköy reservoir determined generally to be Class I and A1 water. In conclusion, Kayalıköy reservoir has water suitable for drinking, agricultural irrigation, and aquaculture and was classified as having oligomesotrophic character.

Accumulation of heavy metals in the physical and biological systems of Lake Koka, Ethiopia: Implications for potential health risks

AbstractLake Koka has several important socioeconomic uses, hydroelectric power generation, domestic water supply, irrigation, recreation and fishery. It is currently under serious threat, however, because of point and nonpoint pollution inputs. The objective of the present study was to examine the concentration of heavy metals (Mn, Cr, Pb, Zn, Cu, Ni and Cd) and their bioaccumulation, and biomagnification factors along the lake's food chain in order to assess the potential human and ecological health risks. Water, sediment and plankton samples were collected from seven sampling sites and fishes were purchased on site from fishers. The analyses were performed using a graphite furnance atomic absorption spectrophotometer. Heavy metals levels in the sediment samples were ranked in the order of Mn > Cr > Pb > Zn > Cu > Ni > Cd. Similarly, the metal concentration in the fish muscles was Cr > Cu > Pb > Cd. The sediment bioaccumulation factor (<1) and water bioaccumulation factor (>1) for Cd, Pb and Cr indicated the lake water exhibited higher concentrations than the sediment. In parallel, the Cr biomagnification factor for zooplankton, catfish, Nile tilapia and common carp was 1.63, 1.18, 1.36 and 2.28, respectively. The Cr concentrations at the Modjo (or Mojo) Upstream, Modjo Downstream and Kentare sites, and the Pb concentrations at riverine sites were above the permissible limits established by the World Health Organization. Cr ranked as fish species > zooplankton > phytoplankton, being above the permissible limits in catfish, Nile tilapia and common carp. Generally, the weekly intake estimates were considerably lower than the tolerable human intake values provided by WHO and others. However, Cr biomagnified along the trophic levels ultimately reaching the top consumers, with Cr (VI) being carcinogenic. The lake is a major fishery source, indicating care must be taken in regard to the weekly intake of the fishes, particularly common carp.

The calculation of solar energy used by hot water systems in permafrost region: An experimental case study for Yakutia

This paper presents a mathematical model for the collection and efficient use of solar energy in hot water systems at permafrost regions. A case study was presented for northern territories of the Russian Federation in the Republic of Sakha (Yakutia). Daily maximum diffuse solar radiation on a horizontal and inclined surface was predicted during the year taking into account cloud coverage. The cloud coverage data was taken from the results of five-year monitoring on the heliometric station of the Yakutsk city. The modelling of the hourly, daily, monthly, and annual amount of solar radiation was performed. The mathematical model was turned and finally proved by experimental data obtained from the testing rig. The modelling of the domestic hot water supply system of particular northern territories was performed using solar energy and energy storage. Both models were integrated and verified by experimental data accounting a seasonal fluctuation. The estimation of the solar energy potential for practical application in Yakutia was executed. The operating features of permafrost regions were analysed by the developed experimental unit. The application of solenoid valve reduces the heat losses during the night by 57% in June and by 69% in November. The case study provides the results of modelling and efficient use of solar energy for different daily water flow rates during January and June. The results of the case study show the possibility to use of solar energy in a hybrid energy system at permafrost regions, decarbonize the energy input and contribute regional sustainability of northern territories.

Use of slag-media filter for treating drinking water

Filtration is a very important process for all domestic water supply systems. Prior to filtration, screening and sedimentation processes will remove large proportion of suspended matter, but they do not effectively remove fine floc particles, colour, dissolved minerals and microorganisms. Often river sand is used as a filter media for domestic water treatment. As river sand is getting depleted, it is apt to have an alternative or substitute material (in place of sand) for treatment of domestic water supply. With this motivation some of the feasible and economical solutions that have emerged in recent years are to reuse the industrial process wastes. Among the various alternatives considered, the materials which are close to meeting the quantity demand of the filter media aggregates are slag, from ferrous industries. In this study, the filtration efficiencies of conventional sand and granulated slag filter media are compared by passing three known concentration of synthetic solutions having a total suspended solids concentration i.e. TSS= 160 mg/L, 210 mg/L and 370 mg/L respectively at a known infiltration rate i.e. 4l/hr. The filters were backwashed periodically. The efficiency of conventional sand filter and granulated slag filter were studied by measuring outflow water flux and head loss occurring in both the filter columns.

Optimal Distribution of Heat Collecting Area of Two Collectors in Solar Water Heating Systems

In view of the large seasonal temperature difference, and the large temperature difference between day and night, difficulty in supplying domestic hot water supply in high altitude area, and the contradiction between low efficiency and cost of single type solar collector system, a hybrid heat collection system based on two different types of solar collectors has been considered in this paper, and a multi-objective optimization model for the heat collecting area optimization of the hybrid solar collectors has also established to solve the above problems. Besides, a fast and effective multi-objective optimization method was proposed for solving of this multi-objective optimization model. This method is based on the fast non-dominated genetic algorithm and the multi-objective decision-making analytic hierarchy process, and was used to analyze the practical hot water supply in a farm in Guoluo zone. The research results shown that this proposed optimization algorithm can quickly and effectively complete the heat collecting area distribution of two different types of collectors in the combined heat collecting system given a certain weight of system cost and heat collecting area. Under the premise of guaranteeing sufficient hot water supply, the system cost is significantly reduced. Therefore, the problem of difficulty and high cost of hot water supply in the plateau region is solved, which has a good practical significance.

An assessment of hydrologic factors that influence contaminant concentrations determined from domestic well-water samples

Open borehole wells in fractured crystalline rock are commonly used for domestic water supply. Concentrations of contaminants present in the well water, typically collected from the tap after some degree of purging, are weighted average concentrations. In this study, factors which influence sample concentrations collected from domestic wells are evaluated through the use of conceptual models and confirmatory field tests. Focus is on the extent of drawdown during sampling, distance between the pump inlet and contaminated fractures, relative fracture transmissivity, fracture discharge rate into the borehole, and the hydraulic head distribution of the fractures. Simplified spreadsheet models were developed to assess the relation between these factors and sample concentrations. The models show that in addition to fracture transmissivities, drawdown in relation to fracture head plays a significant role in how much water recharges a well from each fracture, yet it is rarely measured when sampling domestic wells. To evaluate the extent of drawdown that may occur under typical household usage, water levels were monitored in three domestic wells. Pumping tests were conducted in three wells to measure changes in concentration as a function of pumping duration. Downhole profiling was conducted to examine how pumping induces changes to water quality within the wellbore. The results indicate that these factors can have a strong influence on contaminant concentrations in samples collected from these wells. As such, the weighted averaging factors should be considered in sample collection, in data interpretation, in assessing exposure risk and in mapping contaminant distributions.

A novel filtration system based on ceramic silver-impregnated pot filter combined with adsorption processes to remove waterborne bacteria

Halving the proportion of the people without sustainable access to safe drinking water and basic sanitation is among the Sustainable Development Goals (SDG). Lack of access to safe drinking water has been associated with the prevalence of waterborne diseases. Due to this reported association, the development of household water treatment devices has been an alternative to improve the quality supply of domestic water. In this study, we aimed to evaluate the performance of a ceramic silver-impregnated pot filter (CSF) system coupled with an adsorption process, composed of silver-impregnated granular activated carbon and zeolite (CSF + GAC-Z), to remove waterborne bacteria Escherichia coli and Salmonella spp. from spiked water. The performance of this system was compared with the conventional CSF system. In this respect, we evaluated six CSF and six CSF + GAC-Z using spiked water with 103 and 102 CFU/mL of E. coli and Salmonella spp. The mean percentage of removals ranged between 98% and 99.98%. The highest bacterial removal efficiency was recorded by the CSF + GAC-Z (99%) and CSF (99.98%) for E. coli and Salmonella spp., respectively, but no significant statistical differences were found between filtration systems. Our findings suggest that the CSF + GAC-Z system was effective in the removal of waterborne bacteria from spiked water.

Variation in existing domestic service level of pipe-borne water supply and associated challenges in a tourism destination of Uyo Capital City, Nigeria

Domestic water supply plays a very significant role in the day to day life of humans in the global society and without water, life cannot be continued and that while water provisions are one of the basic requirements for human’s survival. This study therefore examined the evaluation of pipe borne water supply in Uyo Capital City, Akwa Ibom State, Nigeria. In an effort to approximate pipe borne water supply in the study area, the research was hinged on the following objectives, to examine variation in the existing domestic service level of pipe-borne water among communities in the study area and to examine the challenges associated with pipe-borne water supply in the area. Furthermore, a multistage sample technique was used to circumvent a practical difficulty in sampling the study area as the region was delineated into six zones. Geographic Information System was employed to collect coordinates while questionnaire was also used for data collections. 400 copies of questionnaires were purposively administered to the respondents in different zones as follows; Uyo (197), Ibesikpo-Asutan (98), Uruan (45), Ibiono-Ibom (9), Itu (30) and Nsit Ibom (21). Nevertheless, additional 25 questionnaires representing about 10% of the staff (248) of Akwa Ibom Water Company Limited were interpreted with statistical techniques. For hypothesis one, which states that there is no significant variation in the existing domestic service level of pipe-borne water among communities. One way analysis of variance was used and it was discovered that existing service level of pipe-borne water does not differ significantly among communities in the study area (p = 0.81. This result was further supported by Water Production and Supply Intensification Model. Grounded on the findings, it is recommended that water distribution network and supply should be expanded to all the communities within the study area by the government. It is also recommended that the government should partner with organisations for a viable pipe-borne water supply to its residents in the area.

Efficiency of gamma radiation technology in decontamination of wastewater from Soba Station-Khartoum Sudan

In Sudan the expense of municipality treatment is expanding with more strict environmental obligations. Radiation technology for handling of industrial and domestic water supply is presently under study in many countries. The expenses for the wastewater treatment by radiation technology are comparable with that of the other modern technology of treatment systems. This study focuses on using of various radiation doses to handle samples of municipal wastewater collected from Soba wastewater station south of Khartoum-Sudan. The experimental results confirmed that some physicochemical parameters like pH, DO, BOD5, COD, TSS, FOG, and Total phenols were decreased with increasing absorbed doses. Other parameters like Electrical conductivity (EC) and Hardness were not affected by radiation doses. TDS, turbidity decreased up to 50 K rad and then increased with increased in radiation doses. All parameters are within the permissible level in Sudan for discharge to surface water. Gamma-irradiation has shown to be effective in removing organic contaminants from the sewage water and sludge. Gamma-irradiation opens door for possible reuse of irradiated sewage water and sludge. The whole experimental issues involving the management of disposed materials must be put in mind when we are assessing the benefits of applying technology of radiation for treating all municipality issues in Khartoum city.

Groundwater modeling in data scarce aquifers: The case of Gilgel-Abay, Upper Blue Nile, Ethiopia

Groundwater (GW) is the main source of domestic water supply in Ethiopia (85%), however, despite widespread acknowledgement of its potential for resource-based development and climate change adaptation, the sector is still quite under-investigated. This is mainly due to the scarcity of in situ data, which are essential to building robust impact models. To address this, we developed a fine-resolution (500 m) GW model using MODFLOW-NWT, focusing on the Gilgel-Abay Catchment located in the Upper Blue Nile basin, fed with daily distributed input forcings of recharge and streamflow simulated by the Coupled Routing and Excess Storage (CREST) hydrological model. The model was calibrated against instantaneous observation records of GW table for 38 historical wells, and validated at selected sites using time series data collected from the Citizen Science Initiative (PIRE CSI), and the Innovation Lab for Small Scale Irrigation (ILSSI) project. An RMSE of 14.4 m (1.8% of range) was achieved for calibration and same for validation was 18.21 m and 15.76 m at the PIRE CSI and ILSSI sites, respectively. The findings of this research indicate substantial physical GW resource availability in the Gilgel-Abay region. Moreover, we expect the model to have multiscale future applications. These include obtaining dynamically downscaled boundary conditions for a local-scale GW model, to be developed in the next phase of our research. Further, an upscaled version of this model to encompass the entire Tana Basin would be developed to simulate lake-aquifer interactions. Finally, the approach of this research combining different types of datasets (e.g., reanalysis products, satellite data, citizen science data, etc.) is adaptable to other global data-scarce regions. Moreover, the method overcomes specific challenges associated to in situ data scarcity, limited knowledge on GW resources availability in the area, interaction with complex boundary conditions, and sensitivity under meteorological boundary forcings.

Impact assessment on water harvesting and valley dams

Gravity dam is one of the biggest structures built on the Earth. It is known as a life line structure, as it serves the purpose of irrigation, hydro-electric power generation, flood control, domestic and industrial water supply etc., which are important for human existence. This makes dam as a reliable structure. For this reason, dam should always be designed for highest safety. Dam is one of the hydraulic structures constructed to serve particular functions. It is a water control feature to impound water supply, to divert water from a water course, or to raise the elevation for water body. In supplying the water to the consumers, a dam holds it from flowing into the pipe, tunnel and conduit. Earth fill dams are a good alternative to dugouts where larger volumes of water must be stored at a reasonable cost and suitable site conditions exist. Proper design and construction is essential for dams; otherwise they will fail from washouts or seepage losses. If water quantity is your main priority, then a dam could be the best option. If better water quality is the important factor, a dugout is probably a better option. Take the time to properly plan, construct, inspect and maintain your dam, and it will be a valuable water resource for your farm for many years to come. However, poor management of dams can cause problems and disasters in terms of safety of dam and how it affects the people and the environment. This study focuses for conducts how the design, operator and maintenance of dam to be ensure it is safety.

Physicochemical and Heavy Metals Characteristics of Soil from Three Major Dumpsites in Ilorin Metrpolis, North Central Nigeria

Impact of waste disposal and management is a worldwide phenomenon leading to health impact most especially in underdeveloped and developing world. This study was undertaken to assess the major contaminants in some municipal waste disposal sites and the prospective impact to the surrounding domestic water supply source as well as the impact on the health of the people in the city. This is carried out by studying variousphysico-chemical parameters of soil which were collected from three municipal dump locations namely; Ita-Amodu, Sawmill garage and Kuntu areas in Ilorin metropolis, Kwara State Nigeria. The geochemistry of the dumpsites were studied with respect to important parameters such as pH, electrical conductivity, temperature, sulphates, chlorides, nitrates, moisture content, organic matter and heavy metals having the following constituents present in its composition- Cadmium (Cd), Lead (Pb), Zinc (Zn), Iron (Fe), and Copper (Cu). The study revealed that the three different soils samples: “(A) Ita-Amodu”, “(B) Sawmill Garage”, and “(C) Kuntu”) have pH of 7.1, 7.2 and 6.8, respectively. Temperature of 24.2, 26.4, and 28.0 oC, Organic matter compositions of 0.95%, 0.73%, and 1.14%. The Moisture contents were 3.93%, 2.89%, and 3.48% respectively. The chloride contents of the samples was found to be 31.76 mg/L, 48.98 mg/L, and 91.63 mg/L, while nitrates were found to be 0.10 mg/L, 0.06, mg/L and 0.23mg/L, with a sulphate values of 1.96 mg/L, 2.35 mg/L, and 2.14 mg/L. The conductivities were 1.79 μs/cm, 2.23 μs/cm, and 1.15 μs/cm respectively. Heavy metal analysis from the waste soil were found to contained copper (Cu) - 0.03 mg/L, 0.028 mg/L, and 0.031 mg/L, zinc (Zn) - 0.04, mg/L 0.009 mg/L, and 0.066 mg/L), cadmium (Cd) - 0.516 mg/L, 0.62, mg/L and 0.048 mg/L), Lead (Pb) - 0.063 mg/L, 0.07 mg/L, and 0.056 mg/L), and iron (Fe) -0.518 mg/L, 0.62 mg/L, and 0.190 mg/L. 
 Keywords: Dumpsites, Heavy metals, Ilorin, Moisture contents, Nitrates.

Energy and exergy analyses of a novel seasonal CCHP system driven by a gas turbine integrated with a biomass gasification unit and a LiBr-water absorption chiller

Combined cooling, heating, and power systems have been studied extensively because of their great potentials. Accordingly, in the present study, an innovative trigeneration system including a gas turbine cycle, a gasification unit, a heating unit, alongside a single effect absorption refrigeration cycle is proposed. The system operates on natural gas and municipal solid waste (MSW) for cooling, heating, and power generation. The designed system was simulated using Engineering Equation Solver (EES) software through two scenarios; constant power output and constant biomass feed rate, considering seasonal and annual periods. In the first scenario, considering the constant power capacity, the basic design state was considered with the biomass mixing ratio of 50%, and the results of the seasonal study showed that the system capacity is 30 MW, 41.9 MW, and 39.24 MW in terms of electricity, heating, and cooling, respectively. The exergy analysis revealed that the combustion chamber, the evaporator of Heat Recovery Steam Generator (HRSG), and the gasifier in both hot and cold seasons have the highest exergy destruction rate, while the economizers and the evaporators of both HRSGs have the lowest exergy efficiency. The constant mass flow rate of MSW was assumed to be 1.5 kg/s and accordingly, the feed rate of natural gas was also 1.5 kg/s for the mixing ratio of 50% in basic design state of the second scenario, and the results indicated that the annual average capacity of the system for electricity, heating, and cooling generation is 27.43 MW, 40 MW, and 34.15 MW, respectively. Furthermore, the system was capable of providing the domestic hot water supply of end-user with an average capacity of 7.5 MW during a year. The annual Energy Utilization Factor (EUF) and the annual exergy efficiency of the overall system were shown to be 71.25% and 30.79%, respectively.

Design and performance evaluation of a wall mounted solar concentrating collector

In this study, a wall mounted solar concentrating collector with parabolic and involute mirrors combined with an evacuated glass tube is designed to boost the solar energy collection for domestic hot water supply during winter. To optimize the device, the mirrors' parameters are varied, and the amount of collected energy in each case compared through ray tracing simulation. The results show that with the optimal mirror shape, the amount of collected energy is 5.5 times bigger than when the evacuated glass tube is set alone. This system will be considered sufficiently useful as it can reduce the high cost component of the evacuated glass tubes by replacing them with inexpensive mirrors.

A promising water supply scheme for Khomutovo village (Irkutsk district, Irkutsk region)

The article proposes a water supply scheme for Khomutovo village. The authors describe regulation options for domestic and drinking water supply from the existing water intake facility in Dzerzhinsk under uniform operation of pumps using a regulating capacity and a frequency converter without intermediate tanks.

Thermal performance of triplex-tube latent heat storage exchanger: simultaneous heat storage and hot water supply via condensation heat recovery

In refrigeration system, refrigerant condensing will release a lot of heat. Using condensation heat from cold storage refrigeration system to provide heat for domestic hot water preparation and industrial hot water supply promotes energy conservation, and latent heat thermal energy storage (LHTES) has unique advantages. Compared with the shell-and-tube heat exchanger, the triplex-tube heat exchanger (TTHE) can achieve simultaneous heat storage and hot water preparation, but few studies have investigated the thermal performance. A mathematical model of TTHE is established by enthalpy method, and the dynamic characteristics has been studied. The results show that liquid sensible heat transfer, latent heat transfer and solid sensible heat transfer are three stages experience in the whole process. The heat storage rate increases and the heat release rate decreases gradually with the opposite trend, but finally reaches to balance with a stable value. The higher the HTF inlet temperature is, the higher the outlet temperature is, but the temperature difference in stable stage is smaller. With the increase of mass flow rate, its effect on heat release gradually weakened. Under the calculation conditions, phase change material with 80 °C transformation temperature for cold storage refrigeration system condensing heat recovery is reasonable.

Impacts of climate change on reservoir water availability, quality and irrigation needs in a water scarce Mediterranean region (southern Portugal)

Future climate for the Mediterranean climatic region is expected to bring an increase in temperatures, decrease in the precipitation quantity and shifts in the seasonal precipitation pattern. Although the impacts of climate change on water resources have been relatively well explored for the Mediterranean climatic region, the specific consequences for reservoirs and, in particular, water availability and irrigation issues have been less studied. The objective of this work is two-fold: (i) to assess the impacts of future climate changes on water resources availability, quality (focusing on phosphorus loads as this is the limiting nutrient for eutrophication) and irrigation needs for two multipurpose reservoirs in southern Portugal; (ii) to suggest climate change adaptation strategies, especially for the agricultural sector. To this end, the SWAT model was first calibrated against existing data on reservoir inflows as well as phosphorus loads. Then, SWAT was run with climate derived EURO-CORDEX models (RCA4/RACMO22E) for four periods (1970–2000, 2010–2040, 2040–2070 and 2070–2100). Water availability was analysed using the Water Exploitation Index (WEI) that was calculated for both reservoirs combining changes of inflows and irrigation requirements. The results indicated that climate change will negatively impact water availability in both reservoirs, especially under RCP8.5. In the case of the Monte Novo reservoir, future domestic water supply could be constrained by water quality problems related with phosphorus loads. For Vigia reservoir, the high water exploitation will lead to water scarcity problems, mainly as this reservoir on present-day conditions is restrictive on irrigation requirements. Adaptation strategies such as the implementation of high end technology (e.g. soil moisture and plant water stress probes, satellite imagery and drones to evaluate water stress – NDVI) as well as the renewal of the irrigation network and adequate crop selection can help attenuating the effects of climate change on the water resources in this region.

Geospatial and statistical interpretation of lineaments: salinity intrusion in the Kribi-Campo coastland of Cameroon

This study detected, mapped and analysed lineaments from Landsat-8 satellite images of the coastal area of Kribi-Campo, Cameroon. Kribi, a fast-growing coastal city with a youthful population whose main industry is agriculture, is currently under great pressure due to the influx of internally displaced persons, victims of the current socio-political crisis in the western part of Cameroon. With the growing demand for food and water resources, it has been reported that saline soils and groundwater are affecting the agricultural productivity and domestic water supply of the area. This paper investigates the lineaments network in this area to understand its spatial distribution, its extent and the potential effect on inland intrusion of saline water. The datasets, including Landsat-8 imagery, geological data and a digital elevation model were processed using principal component analysis and filtering techniques. Linear features were enhanced based on textural changes of false colour composite images to describe fractures, faults and hydrology features. 390 effective lineaments were extracted automatically and manually from those images and analysed based on length, density and orientation using statistical analysis. But before this processing, non-effective lineaments that may correspond to terraces, linear valleys, cliffs, or tonal contrast as well as to human activities have been deleted. The effective lineaments range in length from 95 to 4910 m with an average of 1171 m. Although the lineaments are not isotropic, their perpendicular orientations to the coast suggest potential intrusion of saline water into regional groundwater resources and farmlands. The paper presents a combined technique of geospatial and statistical analysis in the interpretation of lineament effects which have the potential to inform on salinity intrusion in coastlands. The electrical conductivity of 50 groundwater samples collected in the study area are used to validate the impact of lineaments on seawater intrusion.

Multiyear Links between Water Chemistry, Algal Chlorophyll, Drought-Flood Regime, and Nutrient Enrichment in a Morphologically Complex Reservoir.

This investigation targeted the largest morphologically complex reservoir (Soyang) in South Korea during 1992–2013. It is a prominent source of domestic water supply, irrigation, flood control, and hydroelectric power generation. Therefore, this investigation focused on regional- to global-scale applications. We revealed the empirical links between chlorophyll (Chl-a) and total nitrogen (TN) and total phosphorus (TP), the impact of the monsoon regime on nutrients, and flood and drought regime. Further, we investigated the trophic status dynamics, tendencies of water chemistry factors, and valuation of zonal water chemistry by the application of a modified multimetric water pollution index (WPI). The physicochemical indicators illustrated significant disparities among the Lacustrine (Lz), Transition (Tz), and Riverine (Rz) zones. The solid contents (TSS) displayed a significant increase in the lake zones in the order of Lz (4.58 ± 13.7 mg/L), Tz (6.16 ± 16.2 mg/L), and Rz (7.38 ± 18.9 mg/L). However, TP and allied chemical species revealed an inverse relationship with the TN:TP ambient ratios. Nevertheless, Chl-a displayed sharp interzonal fluctuations from the Lz (2.90 ± 3.29 µg/L) to Tz (4.61 ± 4.98 µg/L). The seasonal deviations, however, exposed divergent heterogeneities among the TSS, TN, TP, and Chl-a. The regression plot between the observed and predicted Chl-a in the Soyang reservoir displayed a very strong relationship (R2 = 0.997). The seasonal and interannual variations of trophic status displayed a higher impact of precipitation, particularly in the case of TP and Chl-a. The flood years indicated phosphorus limitations, while drought years alluded to the non-algal light limitations (biogenic turbidity). Water temperature (WT), dissolved oxygen (DO), biological oxygen demand (BOD), TSS, TP, and Chl-a displayed decreasing trends in the ambient water. In contrast, pH, chemical oxygen demand (COD), electrical conductivity (EC), and TN displayed increasing tendencies by the application Mann–Kendall trend analysis. The WPI outcomes designated Lz with excellent water quality while Tz an Rz indicated good water quality. It also indicated impending sedimentation tendencies in the Rz. In conclusion, our findings indicated fluctuating rainfall patterns (drought and flood conditions) that significantly impacted the Soyang reservoir water quality, flood and drought severity, and trophic status of the reservoir. This study highlights the requirements of further studies to substantiate the drought and flood dynamics and their impacts on nutrients and overall water quality status.

Melting Himalayan Glaciers Threaten Domestic Water Resources in the Mount Everest Region, Nepal

Retreating glaciers and snowpack loss threaten high-altitude communities that rely upon seasonal melt for domestic water resources. But the extent to which such communities are vulnerable is not yet understood, largely because melt contribution to water supplies is rarely quantified at the catchment scale. The Khumbu Valley, Nepal is a highly glaciated catchment with elevations ranging from 2000-8848 m above sea level, where more than 80% of annual precipitation falls during the summer monsoon from June to September. Samples were collected from the rivers, tributaries, springs, and taps along the major trekking route between Lukla and Everest Base Camp in the premonsoon seasons of 2016-2017. Sources were chosen based upon their use by the communities for drinking, cooking, bathing and washing, so the sample suite is representative of the local domestic water supply. In addition, meltwater samples were collected directly from the base of the Khumbu Glacier, and several rain samples were collected throughout the study site. Meltwater contribution was estimated from d 18 O isotopic data using a two-component mixing model with the Khumbu glacial melt and pre-monsoon rain as endmembers. Results indicate between 34-90% of water comes from melt during the dry, pre-monsoon season, with an average meltwater contribution of 65%. With as much as two-thirds of the dry-season domestic water supply at risk, the communities of the Khumbu Valley are extremely vulnerable to the effects of climate change as glaciers retreat and snowpack declines.