Data for: Influence of cryosphere outflow and land cover on stream water quality in Central Asia's glacierized catchments

Description

Stream water pH, temperature, electrical conductivity, and nitrate and phosphate concentrations are provided for four catchments (485 – 13 500 km2), all with glaciers and major urban areas in Central Asia. The catchments are: Kaskelen (Kazakhstan), Ala-Archa (Kyrgyzstan), Chirchik (Uzbekistan) and the Kofarnihon (Tajikistan). Measurements were made in stream water, groundwater, reservoir and lake samples over a 22-month period at fortnightly intervals from 35 sites. The water samples were collected at fixed locations along the main channel from 10 – 20 km downstream of the periglacial headwaters to the lowlands, from large tributaries, and from three deep wells, two wells that were artesian, and from three further springs. Sample collection started between April and July 2019 and ended between October 2020 and January 2021 dependent on the country. In addition, data are provided for cryosphere samples. Snow and glacial melt water samples were collected during the summers of 2019, 2020 and 2021 at the Tuyuksu (KZ) glacier, in 2019 and 2020 at the Golubin (KG) glacier, and at the Barkrak and Tekesh glaciers (UZ) in 2020. The snow samples were collected from snow pits using plastic scoops, placed in plastic bags, melted at room temperature, and filtered and stored as the other water samples. The snow pit sampling was most extensive in KZ where, in 2019, samples were collected from 6 cm layers from the top to the bottom of the snow pit. In 2020, the snow pit was divided into three equal vertical layers of the overall depth of 162 cm and one sample was taken from each layer. In Kyrgyzstan, the cryosphere samples (snow, glacial ice and glacial melt) were collected in 2019 and 2020. In Uzbekistan, 13 samples were collected from the Tekesh and Barkrak glaciers in June and July 2020. In Kazakhstan, at least three water samples were collected in immediate proximity of the Tuyuksu glacier terminus. Water samples were also collected from the outflow of Gorodetskiy and Morennyi rock glaciers and the meltwater from the permafrost active layer in the Ulken and Kishi Almaty headwaters. In total, cryosphere samples were taken at 39 unique locations, and the pH, EC and water temperature were measured in situ except were samples required melting, and NO3--N and PO43--P was measured on return to the laboratory. Not all analytes could be measured in every sample. The sampling and analysis methods are described in the publication ‘Influence of cryosphere outflow and land cover on stream water quality in Central Asia's glacierized catchments‘. The R-scripts used to plot the data and run an ANOVA analysis are included.

Steps to reproduce

Water was sampled using a plastic syringe and filtered through a 0.45μm syringe filter (Fisher Scientific, part No. 15216869) in the field into a 30 ml universal plastic screw cap tube. The samples were stored in a portable fridge and analyzed in a laboratory within 24 hours at room temperature. Water temperature, electrical conductivity (EC) and pH were measured in the field using a hand-held field meter (Hanna Instruments Inc, model HI 9812-5) and combination probe (Hanna Instruments Inc, model HI 1285-5). The portable meters were calibrated before each day of sampling. Nitrate and phosphate concentrations were measured using a laboratory spectrophotometer (Hach Lange Ltd., model DR3900) and the manufacturer’s reagent kits: nitrate cuvette test (part Nr. LCK 339), phosphate ortho/total cuvette test (part Nr. LCK 349) and iron trace cuvette test (part Nr. LCK521). Calibration of the spectrophotometer was checked using manufacturer standards (part Nr. LCA 721) before each analysis using a one-point calibration. Every two months, a set of three standard solutions for each analyte was prepared to check calibration drift with a ±10% deviation considered acceptable. Nitrate and phosphate concentrations were reported in mg L-1 of NO3--N and PO43--P. The detection limits were 0.23 mg N L-1, 0.05 mg P L-1 and 0.01 mg Fe L-1. Dissolved iron concentrations were found to be very close to, or below, the limit of detection at all sites, and therefore dissolved iron measurement was stopped after six months given cuvette and standard costs.

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