Meltwater hydrochemistry at four glacial catchments in the headwater of Indus River

Understanding the hydrochemical functioning of glacierized catchments of the Upper Indus Basin in Ladakh, Indian Himalayas

Recent studies have endorsed that surface water chemical composition in the Himalayas is impacted by climate change-induced accelerated melting of glaciers. Chemical weathering dynamics in the Ladakh region is poorly understood, due to unavailability of in situ dataset. The aim of the present study is to investigate how the two distinct catchments (Lato and Stok) drive the meltwater chemistry of the Indus River and its tributary, in the Western Himalayas. Water samples were collected from two glaciated catchments (Lato and Stok), Chabe Nama (tributary) and the Indus River in Ladakh. The mildly alkaline pH (range 7.3-8.5) and fluctuating ionic trend of the meltwater samples reflected the distinct geology and weathering patterns of the Upper Indus Basin (UIB). Gibbs plot and mixing diagram revealed rock weathering outweighed evaporation and precipitation. The strong associations between Ca²⁺-HCO₃^-, Mg²⁺-HCO₃^-, Ca²⁺-Mg²⁺, Na⁺-HCO₃^-, and Mg²⁺-Na⁺ demonstrated carbonate rock weathering contributed to the major ion influx. Principal component analysis (PCA) marked carbonate and silicates as the most abundant minerals respectively. Chemical weathering patterns were predominantly controlled by percentage of glacierized area and basin runoff. Thus, Lato with the larger glacierized area (~ 25%) and higher runoff contributed low TDS, HCO₃^-, Ca²⁺, and Na⁺ and exhibited higher chemical weathering, whereas lower chemical weathering was evinced at Stok with the smaller glacierized area (~ 5%). In contrast, the carbonate weathering rate (CWR) of larger glacierized catchments (Lato) exhibits higher average value of 15.7 t/km²/year as compared to smaller glacierized catchment (Stok) with lower average value 6.69 t/km²/year. However, CWR is high in both the catchments compared to silicate weathering rate (SWR). For the first time, in situ datasets for stream water chemical characteristics have been generated for Lato and Stok glaciated catchments in Ladakh, to facilitate healthy ecosystems and livelihoods in the UIB.

Assessment of spatio-temporal variations of selected water quality parameters of Lake Ziway, Ethiopia using multivariate techniques

Excess agrochemicals input from agricultural activities and industrial effluent around Lake Ziway catchment can pose a serious threat on the lake ecosystem. Lake Ziway is a shallow freshwater lake found in the northern part of the Ethiopian Rift Valley. It is characterized as semi-arid to sub-humid type of climate. Expansions of the flower industry, widespread fisheries, intensive agricultural activities, fast population growth lead to deterioration of water quality and depletion of aquatic biota. The spatial and temporal variations of selected water quality parameters were evaluated using multivariate techniques. The data were collected from nine sampling stations during dry and wet seasonal basis for analysis of fifteen water quality parameters. The physicochemical parameters were measured in-situ with portable multimeter and nutrients were determined by following the standard procedures outlined in the American Public Health Association using UV/Visible spectrophotometer. Mean nutrient concentrations showed increasing trend in all seasons. These sites were also characterized by high electrical conductivity and total dissolved solid (TDS). All the nine sampling sites were categorized into three pollution levels according to their water quality features using cluster analysis (CA). Accordingly, sampling sites Fb and Ketar River (Kb) are highly and moderately polluted in both seasons, respectively. On the other hand, sampling sites at the center (C), Meki river mouth (Ma), Ketar river mouth (Ka), Meki River (Mb), Korekonch (K_o) and Fa in dry season and Ka, C, Ma, Ko, Bulbula river mouth (B) and Fa during wet season were less polluted. Principal component analysis (PCA) analysis also showed the pollutant sources were mainly from Fb during dry season Mb and Kb during wet season. The values of comprehensive pollution index illustrated the lake is moderately and slightly polluted in dry and wet seasons, respectively. Comparatively, the pollution status of the lake is high around floriculture effluent discharge site and at the two feeding rivers (Kb and Mb) due to increasing trends in agrochemical loads. In order to stop further deterioration of the lake water quality and to eventually restore the beneficial uses of the lake, management of agrochemicals in the lake catchments should be given urgent priority.

Imprints of COVID-19 lockdown on the surface water quality of Bagmati river basin, Nepal

COVID-19 pandemic has caused profound impacts on human life and the environment including freshwater ecosystems globally. Despite the various impacts, the pandemic has improved the quality of the environment and thereby creating an opportunity to restore the degraded ecosystems. This study presents the imprints of COVID-19 lockdown on the surface water quality and chemical characteristics of the urban-based Bagmati River Basin (BRB), Nepal. A total of 50 water samples were collected from 25 sites of BRB during the monsoon season, in 2019 and 2020. The water temperature, pH, electrical conductivity, total dissolved solids, dissolved oxygen (DO), and turbidity were measured in-situ, while the major ions, total hardness, biological oxygen demand (BOD), and chemical oxygen demand (COD) were analyzed in the laboratory. The results revealed neutral to mildly alkaline waters with relatively moderate mineralization and dissolved chemical constituents in the BRB. The average ionic abundance followed the order of Ca2+ > Na+ > Mg2+ > K+ > NH4+ for cations and HCO3-> Cl- > SO42- > NO3- > PO43- for anions. Comparing to the pre-lockdown, the level of DO was increased by 1.5 times, whereas the BOD and COD were decreased by 1.5 and 1.9 times, respectively during the post-lockdown indicating the improvement of the quality water which was also supported by the results of multivariate statistical analyses. This study confirms that the remarkable recovery of degraded aquatic ecosystems is possible with limiting anthropic activities.

Distribution and risk appraisal of dissolved trace elements in Begnas Lake and Rupa Lake, Gandaki Province, Nepal

Contamination of the trace elements (TEs) in the freshwater ecosystems is becoming a worldwide problem. This study was carried out to investigate the TEs contamination, and their associated health risk in Begnas Lake and Rupa Lake, Gandaki Province, Nepal. A total of 30 water samples were collected from both lakes during the pre-monsoon season in 2016. The samples were analyzed for the TEs including copper (Cu), lead (Pb), zinc (Zn), nickel (Ni), cobalt (Co), chromium (Cr), cadmium (Cd), manganese (Mn), cesium (Cs), and arsenic (As) using inductively coupled plasma mass spectrometry. The results exhibited that the mean concentrations of all the TEs were higher in Rupa Lake as compared to Begnas Lake except Pb. Principal component analysis and cluster analysis revealed that both the geogenic and anthropic sources were the major contributors of TEs in the lake water. Anthropic activities were considered to contribute the TEs like Zn and Mn in lake water mainly via agricultural runoff, while evaluating the risk of TEs on human health all the elements showed HQ < 1 and CR < 10−4 indicating currently very low health risk concerns. In good agreement with above, the water quality index (WQI) of the Begnas Lake and Rupa Lake was 2.67 and 5.66, respectively, specifying the lake water was safe for drinking and public health concern. This appraisal would help the policymakers and concerned stakeholders for the sustainable management of Ramsar listed freshwater lakes in the Himalayas.

Hydrochemical assessment of the Beeshazar and associated lakes in Central Nepal

Water quality deterioration has threatened aquatic life around the world including Nepal, which has been a serious issue for environmental sustainability and economic development. This study evaluated and interpreted hydrochemical parameters of the Beeshazar and associated lakes in Central Himalaya, Nepal. The study revealed that the water in the lake was slightly alkaline as the average pH was 7.52. The correlation and principal component analysis (PCA) identified both geogenic and anthropogenic processes as the controlling factors of hydrochemistry whereas the cluster analysis (CA) showed relatively more pollution in the associated Laxmi Lake. Also, the water quality index (WQI) classified the water as “good” for drinking purposes (i.e., WQI = 33.90), while the pollution index (PI) values were characterized as sub-cleanness and slightly polluted. In general, both the WQI and PI signify that water in the lake complex is currently safe for drinking purposes. It is further confirmed from the comparative analysis of chemical variables with other lakes in the region, WHO and national water quality guidelines for aqua culture that the most of the analyzed water parameters exhibited relatively low concentrations and were within the prescribed guidelines. However, the elevated concentrations of NO3−and PO43−may pose serious problems for retaining water quality in the future. The results could be considered for future planning and management of the Ramsar Lakes of the lowland areas in the Himalaya and also as a valuable reference for the freshwater researchers at the national and international levels.