Values In River Water Research Articles

Chemical implication of the partition coefficient of 137Cs between the suspended and dissolved phases in natural water

After the Fukushima Daiichi nuclear power plant accident, the terrestrial environment became severely contaminated with radiocesium. Consequently, the river and lake water in the Fukushima area exhibited high radiocesium levels, which declined subsequently. The partition coefficient of 137Cs between the suspended sediment (SS) and dissolved phases, Kd, was introduced to better understand the dynamic behavior of 137Cs in different systems. However, the Kd values in river water, ranging from 2 × 104 to 7 × 106 L kg−1, showed large spatiotemporal variability. Therefore, the factors controlling the 137Cs partition coefficient in natural water systems should be identified. Herein, we introduce a chemical model to explain the variability in 137Cs Kd in natural water systems. The chemical model includes the complexation of Cs+ with mineral and organic binding sites in SS, metal exchange reactions, and the presence of colloidal species. The application of the chemical model to natural water systems revealed that Cs+ is strongly associated with binding sites in SS, and a major chemical interaction between 137Cs and the binding sites in SS is the isotope exchange reaction between stable Cs and 137Cs, rather than metal exchange reactions with other metal ions such as potassium ions. To explain the effect of the SS concentration on Kd, the presence of colloidal 137Cs passing through a filter is significant as the dominant dissolved species of 137Cs in river water. These results suggest that a better understanding of stable Cs dissolved in natural water is important for discerning the geochemical and ecological behaviors of 137Cs in natural water.

Health and ecological risk assessment of heavy metals in water and sediments within a data scarce urban catchment in Tanzania – A case of Ngerengere River, Morogoro Municipality

Low-, middle- and high-income countries, exhibit indications of risks associated with water quality. The study investigated heavy metal concentrations in surface water and sediments within the Ngerengere River and its tributaries (Kikundi, Bigwa, and Morogoro) drain within in the Morogoro Municipality of Tanzania, an Urban Catchment Area (UCA) with limited available data mainly because of inadequate monitoring and reporting capabilities. Analysis of health and ecological risks associated with heavy metal pollution was also carried out using health risk assessments models, pollution indices, and multivariate analysis techniques. Between the dry and wet seasons of 2023, water and sediment samples from (13) sampling stations strategically established along the Ngerengere river and its tributaries were analyzed for six heavy metals (Pb, Cr, Ni, Cd, Cu and Zn) using the Atomic Absorption Spectrophotometer Model Perking Elmer 850 Graphite Furnace and Perking Elmer AS 800 Auto-sampler coupled with a computer interface for operational, displaying and reading the results. The calculated degree of water contamination (Cd) values in river water in both dry and wet seasons ranged from 0 to 6.803 indicating low and high degrees of contamination respectively. Heavy metal concentration in sediment decreases in the order of Zn>Ni>Cr>Cu>Cd>Pb. The non-cancer risk index (HI) via ingestion and dermal pathways in dry and wet seasons for both children and adult groups was <1 hence no non-cancer risk, However, cumulative dermal and ingestion exposure in both children and adults indicated potential cancer risk in dry and wet season. The analysis of ecological risks associated with heavy metal enrichment in the sediment indicated high enrichment of sediments with Cd, Ni and Zn. Conclusively, in wet months, risk indices tend to be low, while in dry months, they typically remain high.

Controlling mechanism and water quality assessment of arsenic in China's Yellow River Basin

Arsenic (As) is a well-known toxic and carcinogen element, and As contamination has gained public concerns worldwide. Mechanisms, sources, and potential health risks of high As in the China's Yellow River Basin (CYRB), a water-deficient area and the largest loess deposition area in the world, remain largely unknown. Hydrogen and oxygen isotopes, major ions, and As were analyzed in 409 river water and 164 groundwater samples in dry season to decipher these problems. Samples were alkaline (pH = 8.0 ± 0.4), and As concentrations (5.29 ± 10.5 μg/L) in the CYRB were above the world average, especially in upstream and midstream. About 9.1% and 13.0% of samples in river water and groundwater had As concentrations above the permissible limit of WHO, respectively. Based on self-organizing map (SOM) analysis, about 50.6% of samples with high As were SO4–Cl–Na type while about 46.4% of samples with low As were HCO3–Ca–Mg type. The δD (−62.5 ± 11.3‰) and δ18O (−8.5 ± 2.1‰) values of river water were higher than the groundwater (δD = −69.7 ± 10.2‰, δ18O = −9.9 ± 1.4‰), and most samples with As >10 μg/L were below the local and global meteoric water lines, indicating the evaporation effect on As enrichment, especially for river water. Evaporites dissolution of loess and ion exchange increased water salinity, accelerated desorption of As and enriched As in CYRB. Meanwhile, oil and coal exploitation contributed to the high As in the northwestern Loess Plateau. Health risk assessment indicated that 41.6% and 59.8% of groundwater samples posed high carcinogenic risk for adults and children, respectively. Therefore, corresponding measures must be implemented in these areas. In the future, As geochemistry in wet seasons in the CYRB and the characteristics among different seasons will be explored. These results highlight the impact of dry climate and anthropogenic activity on As enrichment in arid/semi-arid regions.

Tracking Riverine Nitrate Sources and Transformations in the Yiluo River Basin by Nitrogen and Oxygen Isotopes

The impacts of natural processes and anthropogenic input on riverine nitrate (NO-3) could be identified by NO-3 concentrations and nitrogen and oxygen isotope ratios (δ15N-NO-3 and δ18O-NO-3); however, the effects of variable land use on riverine NO-3 sources and transformations remain unclear. In particular, the human impacts on riverine NO-3 in mountain areas are still unknown. The Yihe River and Luohe River were used to elucidate this question due to their spatially heterogeneous land use. Hydrochemical compositions, water isotope ratios (δD-H2O and δ18O-H2O), and δ15N-NO-3 and δ18O-NO-3 values were utilized to constrain the NO-3 sources and transformations affected by different land use types. The results indicated that ① the mean nitrate concentrations in the Yihe River and Luohe River waters were 6.57 and 9.29 mg·L-1, the mean values of δ15N-NO-3 were 9.6‰ and 10.4‰, and the average δ18O-NO-3 values were -2.2‰ and -2.7‰, respectively. Based on the analysis of δ15N-NO-3 and δ18O-NO-3 values, the NO-3 in the Yihe and Luohe Rivers were derived from multiple sources, and nitrogen removal existed in the Luohe River, but the biological removal in the Yihe River was weak. ② The contributions of different nitrate sources were calculated using a Bayesian isotope mixing model (BIMM) based on δ15N-NO-3 and δ18O-NO-3 values of river water in the mainstream and tributaries with spatial locations. The results revealed that sewage and manure had major impacts on riverine nitrate in the upper reaches of both the Luohe River and Yihe River, where forest vegetation was widely distributed. However, the contributions from soil organic nitrogen and chemical fertilizer were higher in the upper reaches than in downstream ones. The contributions of sewage and manure still increased in the downstream reaches. Our results confirmed the primary impacts of point sources, e.g., sewage and manure, on riverine nitrate in the studied area, and the contributions of nonpoint sources, e.g., chemical fertilizer, had not increased as the agricultural activities elevated the downstream. Therefore, more attention should be paid to point source pollution treatment, and the high-quality development of ecological civilization in the Yellow River Basin should be maintained.

Fe contents and isotopes in suspended particulate matter of Lancang River in Southwest China

Iron (Fe) isotope geochemistry in rivers is crucial for comprehending surficial weathering and geochemical cycle mechanisms. Lancang River is an important channel for material transport between the Tibet Plateau and the oceans of Southeast Asia. In this study, Fe contents and Fe isotope (δ56Fe) compositions in the suspended particulate matter (SPM) are investigated to discuss the rock weathering processes in the Lancang River Basin. The δ56Fe values of SPM range from 0.01 ‰ to 0.21 ‰, with an average of 0.12 ‰, close to the average δ56Fe value of continental crust (0.07 ‰). The results indicate that the fractionation of Fe isotopes is limited caused of weathering process in the Lancang River Basin. Due to the interception of dense dams in the middle and lower reaches (1000–2000 m), the dissolved oxygen (DO) values of river water and the Fe contents of SPM remain at a relatively highest level, whereas the δ56Fe values in SPM are more positive. The positive correlation between chemical index of alteration (CIA) values and the Fe contents suggest that Fe in the tributary SPM may represent the weathering degree of their source areas. The increase of DO in the mainstream water may promote the decomposition and dissolution of SPM, thus increasing the contents of Fe in the remaining SPM, and causing slight positive fractionation of Fe in SPM. This study presents a complete analysis of the Fe isotope's potential utility in identifying the source of SPM. In addition, the Fe isotope may represent some alterations encountered by SPM throughout the runoff process.

Stable isotopic variations (δD and δ18O) in a mountainous river with rapidly changing altitude: Insight into the hydrological processes and rainout in the basin

AbstractHydrological processes play an important role in stable isotopic compositional variations of the river water. The present study includes spatial distributions of stable hydrogen and oxygen isotopes (δD and δ18O) of a Himalayan River (the Teesta) to trace various hydrological processes and their associated roles on isotopic fractionation of river water. The δ18O compositions of the water samples varies between −12.2‰ and −5.4‰ (mean: −8.01‰ ± 1.81‰) and that of δD between −95.1‰ and −38.5‰ (mean: −57.6‰ ± 15.6‰). The observed compositional variation in δ18O, δD and d values of river water is mainly governed through snowmelt input, evaporation, and recycled moisture contribution. The variation of δ18O and δD values point towards an early melting of snow in the basin and a significant contribution of snowmelt to the river water. The orographic induced precipitation front appears to control the hydrological regimes in a distinct manner as reflected in the trend between d values and elevation. The rain shadow affected northern reaches of the basin are characterized with dry & arid climate triggering evaporation whereas, the windward southern side witness temperature influenced evaporation. The study suggests that the differential degree of recycled moisture contribution to the local precipitation is also a key component in bringing the stable isotopic variation in the river water. This varied magnitude of moisture recycling could result from uneven distribution of evapotranspiration and surface water evaporation. Results found that a rapid change in the altitude of a river basin can give rise to different hydrometeorological conditions, thereby resulting in simultaneous operation of almost all the major hydrological processes and a complex isotopic compositional variation in the river water. Also, the rainout percentage in the Teesta basin is found to be higher owing to this rapid rate of elevation increase.

Application of Water Stable Isotopes for Hydrological Characterization of the Red River (Asia)

Fraction of young water (Fyw) and mean transit time (MTT, τ¯) calculated from water isotope profiles are valuable information for catchment hydrological assessment, especially in anthropogenically impacted region where natural conditions may not be decisive to catchment hydrology. The calculation of Fyw and MTT were performed on three subsets of δ18O_H2O data collected at the Hanoi meteo-hydrological station, Red River, in three periods; 2002–2005, 2015, and 2018–2019. The mean (min and max) values of δ18O_H2O in rainwater over the three periods are, respectively, −5.3‰ (−11.0 and −1.2‰), −5.4‰ (−10.7 and −1.4‰), and −4.5‰ (−13.9 and 1.7‰). The corresponding values in river water are −8.4‰ (−9.8 and −6.9‰), −8.5‰ (−9.1 and −7.7‰), and −8.4‰ (−9.5 and −7.2‰), respectively. The mean of Fyw calculated from the δ18O_H2O data for different periods is 22 ± 9%, 10 ± 5%, and 8 ± 3%. Mean transit time is 4.69 ± 15.57, 1.65 ± 1.53, and 2.06 ± 1.87 years. The calculated Fyw (MTT) is negatively (positively) proportional to change in reservoir volume over the three periods, which is logical, since reservoirs tend to keep more water in the catchment and slower down water flow. The strong variation of Fyw and τ¯, two essential variables characterizing the catchment hydrology, represents an anthropogenic impact in the Red River system.

Measurement of Snow Physical Properties and Stable Isotope Variations in the Canadian Sub-Arctic and Arctic Snowpack

ABSTRACT In northern Canada, the annual peak in river discharge is dominated by the seasonal input of snowmelt. As such, climatic changes that alter snowmelt properties and timing will have cascading impacts on the hydrological system as the Arctic warms. Geochemical tracers provide a tool to characterize the various processes governing the seasonal evolution of the snowpack; however, a lack of snow observations from a variety of Arctic landscapes limits the broad applicability of such tracers and further impedes our understanding of the various processes governing snowpack evolution and its ultimate contribution to the spring discharge peak. This study aims to gain a better understanding of the spatial distribution and the temporal evolution of the natural stable isotope signatures of snow from two distinct ecoregions: open tundra and taiga. More specifically, we describe the geophysical and stable isotope properties of the snow cover at Wekweètì (Northwest Territories), a high sub-Arctic taiga site, and within the Greiner Lake Watershed, near Cambridge Bay (Nunavut), an open Arctic tundra site. Results illustrate a link between snowpack formation and stable isotope distributions at both study sites. Stable oxygen isotope ratios of snow (δ 18O-H2O) show a wide range from −41‰ to −17‰ across all snow depth classes; however, heavy isotope enrichment is clearly visible in the bottom snow layers at both sites. Vapour flux from the ground under a strong temperature gradient is considered to be the main driver for this enrichment due to kinetic metamorphism, which is more prominent at the open tundra site. The stable isotope signatures of the bottom hoar layers during winter were found to be similar to river water values sampled during spring and summer, highlighting the need for more in-depth hydrological cycle assessment.

Estimation and comparison of the environmental impacts of acid mine drainage‐bearing river water in the Bor and Majdanpek porphyry copper mining areas in Eastern Serbia

AbstractMining activities in the Bor and Majdanpek mining areas in Eastern Serbia started in 1903 and 1961, respectively. Environmental problems in the Bor mining area began after the opening of the Bor mine. Long‐term pollution of river water in the Bor and Majdanpek mining areas has an environmental impact on East Europe because all of the river water from these mining areas flows into the Danube River. However, the sizes of areas with pollution and the differences between the environmental impacts of the Bor and Majdanpek mining areas are not clear. In order to determine the effects of mining activities on river water in the study area, creation of geochemical maps showing the distributions of sulfate, heavy metals, and arsenic; estimation of threshold values to discriminate anomalous values from background values; and comparison of the environmental impacts of the two mining areas were carried out. High concentrations of SO42−, Fe, As, Cu, and Mn were found in the Bor River, Krivelj River, and Bela River located in the Bor mining area. These rivers are characterized by acidic pH ranging from 2.9 to 6.2. High concentrations of these components were also measured in the Small Pek River and the upper reach of the Pek River. These rivers are located in the Majdanpek mining area and are characterized by weakly alkaline pH (7.3–8.4). The acidic river water in the Bor mining area transports large quantities of heavy metals and arsenic downstream (6,900 t/year of Fe, 42 t/year of As, 910 t/year of Cu, and 187 t/year of Mn). On the other hand, the weakly alkaline river water in the Majdanpek mining area transports smaller quantities of heavy metals and arsenic downstream (160 t/year of Fe, 0.1 t/year of As, 6 t/year of Cu, and 272 t/year of Mn). The environmental impact of the Bor mining area is significantly larger than that of the Majdanpek mining area. In addition, on the basis of the distribution of anomalous values in river water, pollution caused by mining activities reaches the Danube River, which is located more than 100 km from the Bor and Majdanpek mining areas. Concentrations of SO42−, Fe, As, Cu, and Mn in the Bela River in the Bor mining area have been greatly decreased after mixing of acidic polluted water of the Bela River with water of the Timok River containing a high bicarbonate concentration. This fact suggests that river water in the Bor and Majdanpek mining areas has sufficient capacity for neutralization. Considering appropriate countermeasures of environmental reclamation, such as artificial neutralization at some important sources of waste water before discharging the waste water from the mining sites, there is a possibility for environmental reclamation in both mining areas because unpolluted river water in the study area has sufficient capacity for neutralization in a natural system.

Variations of Stable Oxygen and Deuterium Isotopes in River and Lake Waters During Flooding Season Along the Middle and Lower Reaches of the Yangtze River Regions

Stable isotope tracers have been widely applied to water sources and evolution, transforming relations, and pollution sources of various water bodies. This study analyzed the spatial variations of δ2H and δ18O in river and lake waters during flooding season, and revealed the factors underlying their variations along the middle and lower reaches of the Yangtze River based on a field sampling campaign in July 2018. Our results showed that δ2H and δ18O in the Yangtze River water were enriched from the Three Gorges reservoir region to the lower reaches of the Yangtze River, which was closely linked to isotopic variations in precipitation. There was no significant difference in δ2H and δ18O values in the mainstream river waters between the Three Gorges Reservoir Region and Yichang-Chenglingji. However, d-excess values in river water displayed a small variation range. In contrast, δ2H and δ18O values in the lake group from Dongting to Jianghan and Huayang to Poyang Lake were lower than in the lake group from Taihu to the Yangtze Delta. Negative d-excess values were observed in lake water from Taihu to the Yangtze Delta, suggesting the combined influence of enriched isotopic compositions in precipitation and strong evaporative enrichment. Of the lakes, the highest isotopic values were found in Dianshan Lake and Datong Lake, whereas the lowest isotopic values were recorded in Dongting Lake and Poyang Lake because of their direct connection with the Yangtze River. The water regimes of Dongting Lake and Poyang Lake were influenced by the Yangtze River, especially when a high water level of the Yangtze River occurred, and thus altered the isotopic compositions of Dongting Lake and Poyang Lake water. Hence, these findings will provide scientific data revealing the precipitation-river-lake interactions and investigating the rational utilization and management of water resources in the middle and lower reaches of the Yangtze River regions.

Short communication: Isotopic tracing of stormwater in the urban Liesbeek River

The ongoing drought in the Western Cape of South Africa (2014 to present) has called for an urgent need to improve our understanding of water resources in the area. Rivers within the Western Cape are known to surge rapidly after rainfall events. Such storm-flow in natural river catchments in the Jonkershoek mountains has previously been shown to be driven by displaced groundwater, with less than 5% of rainfall appearing in the storm-flow. However, the origin of storm-flow surges within urban rivers in the region remains unknown. In this study, we used stable isotopes in water to illustrate that at least 90% of water in the Liesbeek River during a storm event was rainwater. There was a strong correlation between storm-flow and rainfall rates (P < 0.001, Pearson’s r = 0.86), as well as between the δ18O and δ2H values of river-water and rainwater (δ18O: Pearson’s r = 0.741 (P = 0.001), δ2H: Pearson’s r = 0.775 (P < 0.001)). Storm-flow within this urban river therefore appears to be driven by overland-flow over the hardened urban catchment, rather than piston-flow as seen in natural catchments. Our results support studies suggesting the Liesbeek River could be a target for stormwater harvesting to augment water resources in the city of Cape Town.

Snowmelt runoff and groundwater discharge in Himalayan rivers: a case study of the Satluj River, NW India

The Himalayas are one of the largest cryospheric systems outside the Polar Regions, and include more than 12,000 glaciers spread over an area of about 33,000 km2. The Himalayan glaciers and snow packs retreating at an accelerating rate, thereby creating an alarming situation for the huge population that resides in northwestern India and southeastern Pakistan, as they depend on surface water resources in the region and rivers emanating from the Himalayas. This work attempts to quantify the contribution of different sources such as glacial/ice/snow melt and groundwater discharge to the Satluj River using the stable isotopes based hydrograph separation method at Ropar (foot hill) and Yusufpur in plain of Punjab, India. A mass balance model of three-component mixing has been engaged using the values of δ18O and electrical conductivity of the river water, and its discharge fraction, to estimate the time-varying relative proportion of each component from July 2013 to January 2014. The proportion of glacier melt was found to peak up to ~ 64% at Ropar and ~ 15% at Yusufpur during the wet summer months. The fraction of groundwater discharge was found to vary between 10–20% at Ropar and 25–35% at Yusufpur (Punjab plain) over time. The observed trend of d-excess (deuterium excess) values of river water also suggests that the glaciers and snow packs at higher altitudes contain a significant fraction of snow derived from vapor originating in the Mediterranean region, driven by the mid-latitude westerlies known as western disturbances.

Variations of δ18O in Rivers of Crimea in Winter

The results of studies of variations of δ18O values in river water in Crimea Peninsula in January–February 2015–2017 are given. The variation range of δ18О in river water over the three years of studies never exceeded 3‰. A tendency toward an increase in δ18О in the water of the Salgir, Kacha, Al’ma, Bel’bek, Biyuk-Karasu from their sources to mouths was identified and explained by a decrease in evaporation in the mouth areas of the rivers relative to their sources and upper reaches, and the inflow of isotopically light precipitation (rain and snow) into the rivers in their upper reaches. The values of δ18О in waters of the rivers with regulated stream were found to increase under the effect of the Simferopol Reservoir on the Salgir River and the Izobil’nenskoe Reservoir on the Ulu-Zen’ River. The values of δ18О in the upper reaches of the large rivers of Kacha and Bel’bek (the northwestern slope of the Crimean Mountains) vary from −8.7 to −9.7‰, except for the rivers of Al’ma (−7.7‰) and Kokozka (−10.2‰) because of the different shares of groundwater in the recharge of these rivers.

Determining δ15N-NO3− values in soil, water, and air samples by chemical methods

Soil, water, and air NO3- pollution is a major environmental problem worldwide. Stable isotope analysis can assess the origin of NOx because different NOx sources carry different isotope signatures. Hence, using appropriate chemical methods to determine the δ15N-NOx values in different samples is important to improve our understanding of the N-NOx pollution and take possible strategies to manage it. Two modified chemical methods, the cadmium-sodium azide method and the VCl3-sodium azide method, were used to establish a comprehensive inventory of δ15N-NOx values associated with major NOx fluxes by the conversion of NO3- into N2O. Precision and limit of detection values demonstrated the robustness of these quantitative techniques for measuring δ15N-NOx. The standard deviations of the δ15N-NO3- values were 0.35 and 0.34‰ for the cadmium-sodium azide and VCl3-sodium azide methods. The mean δ15N-NO3- values of river water, soil extracts, and summer rain were 8.9 ± 3.3, 3.5 ± 3.5, and 3.3 ± 2.1‰, respectively. The δ15N-NO3- values of low concentration samples collected from coal-fired power plants, motor vehicles, and gaseous HNO3 was 20.3 ± 4.3, 5.6 ± 2.78, and 5.7 ± 3.6‰, respectively. There was a good correlation between the δ15N-NO3- compositions of standards and samples, which demonstrates that these chemical reactions can be used successfully to assess δ15N-NO3- values in the environment.

An Oxygen Isotope Study of Seasonal Trends in Jinxiuchuan River of Jinan South Mountain

The stable isotope composition of river water contains some information of water cycle and climatic factors, such as precipitation, evaporation and temperature. Oxygen isotopes in river water were monitored at one site in Jinxiuchuang basin of Jinan southern mountain.δ18O values of river water show a variation from-7.82 on July 6 to-9.98 on June 6. The result reveals that the river water was mainly supplied by the precipitation. The isotopic variations at Jinxiuchuan river have strong precipitation patterns owning to different rainfall in summer.

Uranium and strontium isotopic evidence for strong submarine groundwater discharge in an estuary of a mountainous island: A case study in the Gaoping River Estuary, Southwestern Taiwan

To further define the hydro-geochemical circulation in estuary from a mountainous island, over 50 river water samples were collected in three sampling schemes from the Gaoping River Estuary (GRE), the largest river catchment in southwestern Taiwan and were analyzed for major/trace elements, uranium (U) and strontium (Sr) isotopic compositions using multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). Dissolved U and Sr concentrations (0.46–13.8nM and 2.27–86.2μM), as well as U activity ratio (denoted as (234U/238U)) and 87Sr/86Sr (1.145–2.427 and 0.709155–0.712918), vary significantly and show strong seasonal variability. Three characteristic source waters were identified in the study region, seawater (SW), river water (RW), and groundwater (GW or evolved RW). SW has the highest U and Sr concentrations among the three end-members with low and constant (234U/238U) and 87Sr/86Sr. In contrast, RW shows the lowest U and an intermediate Sr concentration, but with medium (234U/238U) and the most radiogenic 87Sr/86Sr. GW has the medium U and lowest Sr content with rather radiogenic (234U/238U) and 87Sr/86Sr, possibly evolved from RW. The GW is most clearly identified in the vertical profile of the near estuary stations. These high (234U/238U) values in RW and GW reflect the outcome of intense weathering in the upper catchment, efficient leaching of α-recoil products in soils. Dissolved Sr and 87Sr/86Sr data confirm similar U mixing scenarios, but the index is more sensitive to water source variations. Estimated fluxes of submarine groundwater discharge (SGD) in the GRE reach a maximum value of 456–2107×1011Lyr−1, implying important contribution to the chemical budget in coastal regions. This study reveals that U and Sr isotopes are useful tracers for monitoring SGD in estuaries.

Hydrograph separation and precipitation source identification using stable water isotopes and conductivity: River Ganga at Himalayan foothills

AbstractThe observed retreat of several Himalayan glaciers and snow packs is a cause of concern for the huge population in southern Asia that is dependent on the glacial‐fed rivers emanating from Himalayas. There is considerable uncertainty about how cryospheric recession in the Himalayan region will respond to climate change, and how the water resource availability will be affected. As a first step towards quantifying the contribution of glacier‐melt water, hydrograph separation of River Ganga at Rishikesh into its constituent components, namely (i) surface runoff, (ii) glacial ice‐melt and (iii) groundwater discharge has been done in this paper. A three‐component mixing model has been employed using the values of δ18O and electrical conductivity (EC) of the river water, and its constituents, to estimate the time‐varying relative fraction of each component. The relative fraction of the surface runoff peaks (70–90%) during winter, due to the near‐zero contribution of glacial ice‐melt, essentially represents the melting of surface snow from the catchment. The contribution of glacial ice‐melt to the stream discharge peaks during summer and monsoon reaches a maximum value of ∼40% with an average of 32%. The fraction of groundwater discharge varies within a narrow range (15 ± 5%) throughout the year. On the basis of the variation in the d‐excess values of river water, it is also suggested that the snow‐melt and ice‐melt component has a significant fraction derived from winter precipitation with moisture source from mid‐latitude westerlies (also known as western disturbances). Copyright © 2010 John Wiley & Sons, Ltd.

Spatial and temporal characterisation of stable isotopes in river water as indicators of groundwater contribution and confirmation of modelling results; a study of the Weser river, Germany†

River water samples were analysed for stable isotopes (deuterium and oxygen-18) collected from 46 sites during spring 2008, and from monthly samples at the outlets of seven sub-basins of the River Weser (46,200 km2 basin area in total) over a five year period from 2003 to 2007, to characterise temporal and spatial isotope patterns of river water. Results indicate a pronounced elevation effect (0.2‰ and 1 to 2‰ per 100 m for δ18O and δ2H, respectively) as well as influence of seawater mixing for a few coastal locations. A lumped parameter modelling approach was used to compare residence times and relative amounts of direct flow, fast and slow groundwater with those derived from a combined water balance and tritium balance modelling approach. Residence times of direct runoff were estimated to be between one and three and a half months. Much longer groundwater residence times are necessary to explain tritium recession in river water. The modelling fits for stable isotope data in river water, derived with residence times and base flow amounts combined from a water and tritium balance approach, emphasise that beneath a characterisation of a direct flow component, seasonal variations of stable isotope values in river water carry information on groundwater contribution.

Hydrogeochemical and Stable Isotope Characteristics of the River Idrijca (Slovenia), the Boundary Watershed Between the Adriatic and Black Seas

The hydrogeochemical and isotope characteristics of the River Idrijca, Slovenia, where the world’s second largest mercury (Hg) mine is located, were investigated. The River Idrijca, a typical steep mountain river, has an HCO3 −–Ca2+–Mg2+ chemical composition. Its Ca2+/Mg2+ molar ratio indicates that dolomite weathering prevails in the watershed. The River Idrijca and its tributaries are oversaturated with respect to calcite and dolomite. The pCO2 pressure is up to 13 times over atmospheric pressure and represents a source of CO2 to the atmosphere. δ18O values in river water indicate primary control from precipitation and enrichment of the heavy oxygen isotope of infiltrating water recharging the River Idrijca from its slopes. The δ13CDIC values range from −10.8 to −6.6‰ and are controlled by biogeochemical processes in terrestrial environments and in the stream: (1) exchange with atmospheric CO2, (2) degradation of organic matter, (3) dissolution of carbonates, and (4) tributaries. The contributions of these inputs were calculated according to steady state equations and are estimated to be—11%:19%:30%:61% in the autumn and 0%:26%:39%:35% in the spring sampling seasons.

Hydrogeochemical characteristics of the River Idrijca (Slovenia)

The hydrogeochemical and isotope characteristics of the River Idrijca, Slovenia, where the world’s second largest mercury (Hg) mine is located, were investigated. The River Idrijca, a typical steep mountain river has an HCO3 Ca2+ Mg2+ chemical composition. Its Ca2+/Mg2+ molar ratio indicates that dolomite weathering prevails in the watershed. The River Idrijca and its tributaries are oversaturated with respect to calcite and dolomite. The pCO2 pressure is up to 13 times over atmospheric pressure and represents a source of CO2 to the atmosphere. δ 18O values in river water indicate primary control from precipitation and enrichment of the heavy oxygen isotope of infiltrating water recharging the River Idrijca from its slopes. The δCDIC values range from −10.8 to −6.6 ‰ and are controlled by biogeochemical processes in terrestrial environments and in the stream: 1) exchange with atmospheric CO2, 2) degradation of organic matter, 3) dissolution of carbonates, and 4) tributaries. The contributions of these inputs were calculated according to steady state equations and are estimated to be -11 %: 19 %: 31 %: 61 % in the autumn and 0 %: 6 %: 9 %: 35 % in the spring sampling seasons.