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Glacier lakes outburst floods (GLOFs) study in the Central Asian region is a very important task in terms of global warming and glacier shrinking. It is expected that ongoing climate changes will lead to an increase in the magnitude and frequency of glacial hazards with profound implications for risks. The appearance and expansion of naturally-dammed lakes in the mountain regions of Uzbekistan poses a threat to downstream communities through the potential for sudden drainage.In this study, we considered a possible flood from failures of natural dams of the two well-known Ikhnach lakes located in the Pskem River basin at an altitude of 2400 m. We simulated the GLOF using the RAMMS: DebrisFlow software. In our scenario the potential debris flow from the Ikhnach Lakes can reach a constructed dam of the Pskem new reservoir located at the altitude of 1020 m. The total length of the analyzed flow path is 34 km. It is known that accurate and up-to-date digital elevation models (DEMs) are important tools for studying mountain hazards. We used such global DEMs as input as ALOS PALSAR, and TanDEM-X DEMs. According to the simulation results of possible floods from the Ikhnach lakes in the Debris Flow module of the software, the following results were obtained: (i) the time of the flood to reach the hydropower station (HPP) area - 14800±700 sec ~ 4.11 hours; (ii) maximum water discharge of flood water at the HPP area – 410±20 m3 s-1; (iii) height of the flood in the HPP area - 1.2 m.The obtained results show that there is no potential disastrous effect of the possible flood from the lakes to the residential area as the lowest settlement along the river bed is located considerably higher than flood risk area. However, possible floods in the lakes potentially can reach and have an effect on day to day dam operation of newly constructed Pskem HPP and its engineering infrastructures. Therefore, flood parameters modeled in the RAMMS can be useful information for designing flood damage prevention structures and reservoir operation.

Meteorological drought generally gets propagated into agricultural and hydrological drought. Hydrological drought is characterized by reduced streamflow in the river regime. Due to the interconnection between different drought types, it is important to analyze the drought propagation time. Propagation from meteorological to hydrological drought is of prime concern, as hydrological drought is having immediate consequences on industry, agriculture, and the water supply system. In the present study propagation time from meteorological to hydrological drought was studied using the spearman rank correlation coefficient for the Tapi river basin of India having semi-arid climatic conditions. Spearman rank correlation was calculated between lagged values of the standardized precipitation index (SPI-1,2,3,4,5,6,7,8,9,10,11,12), and monthly standardized streamflow index (SSI-1). Drought propagation under the influence of the Ukai reservoir was analyzed for Sarangkheda and Ghala gauging stations. Sarangkheda station is in the upstream of the Ukai reservoir whereas, Ghala station is in the downstream. Results indicated that there is a clear influence of reservoir on propagation time from meteorological to hydrological drought. The highest correlation for the Sarangkheda station was observed for SPI-5 and SSI-1, whereas, for the Ghala station, it is for SPI-12 and SSI-1. Propagation time has significantly increased for reservoir-influenced gauging station as compared to gauging station in the natural catchment. The present study is important as information on propagation time under the influence of a reservoir can be useful to the water resource manager, stakeholders, and policymakers for doing the required preparation and taking necessary measures.

The mountains of Central Asia are water towers servicing the arid downstream regions and maintaining irrigation and food production. There are several sources of runoff: liquid precipitation, snowpack, glacier ice, ground ice (including rock glaciers and permafrost), and ground water. The relative contributions of different water sources to stream flow are poorly quantified and its improved understanding will reduce uncertainty in hydrological modelling and projections of changes in water resources. In 2019-21, an extensive sampling programme was conducted to quantify the relative contributions of water sources to stream flow in the Tien Shan and Pamir-Alai using stable water isotope tracers (SWI) of oxygen and hydrogen. Samples of the event-based precipitation, river discharge taken daily or twice-daily at the designated sampling points and every fortnight along the river courses, and water sources were collected in the glacierized catchments in Kazakhstan (Ulken Almaty and Kishi Almaty catchments), Kyrgyzstan (Ala-Archa and Chon-Kyzyl Suu), Tajikistan (Varzob and Kafornihon), and Uzbekistan (Chirchik). The samples were processed using Picarro isotope analyser. A data set of SWI ratios from approximately 6000 samples has been produced and analysed. It is the first comprehensive SWI database in Central Asia contributing to understanding of regional and global isoscapes and water resources. The local meteoric water line (LMWL) was developed from the event-based precipitation samples. It is approximated as δD = 7.6δ18O + 8.7. The values of SWI in precipitation exhibit a clear annual cycle and depend on precipitation type (rain, snow, and mixed). The derived seasonal SWI values are different from those available from the Water Isotopes Database being nearly twice as high in winter. Snow, glacier ice and permafrost exhibit distinct isotopic signatures although these vary between the basins. Glacier ice in the Chirchik basin appears to be more depleted than elsewhere. Rock glaciers were sampled in the Ulken Almaty basin showing SWI ratios similar to those of glacier ice but both are distinct from permafrost. These results point at the feasibility of the application of the mixing model and end-member mixing analysis approaches to the partitioning of runoff and quantifying relative contributions of different water sources in the Tien Shan and Pamir-Alai. This is a policy-relevant task under the conditions of climate change.

This study investigated the link between meteorological and hydrological droughts in two rivers with and without glaciers in Сhirchik river basin of Western Tian Shan. Observed monthly hydrometeorological data was used to estimate Standardized Precipitation Indexes (SPI) and Standardized Streamflow Indexes (SSI) to analyze the hydrological response of snow-glacier fed Pskem and snow-rain fed Ugam rivers in the region. The Pearson correlation coefficient has been used to estimate statistical relations between SPI and SSI indices for the selected rivers. The SPI-SSI correlation coefficient has shown a positive trend with an increase in timescales, and it was more evident in indexes between the 6-month to 12-month timescales in both rivers. The statistical relationships between the meteorological and hydrological drought indexes showed that the SPI-SSI relationship varies with river flow generation and its dynamics, and it was more in the Ugam River than the Pskem River. That indicates snow-dominated Ugam River is more prone to meteorological droughts, whereas the glaciers in the Pskem River basin were buffering hydrological drought and its frequency and severity. Obtained results allow better-informed forecasting of hydrological droughts in the river basin and, consequently, enable efficient water management in agricultural and hydropower sectors.

Central Asia (CA) is considered a hot-spot for climate-change impact on the water-cycle because of a high density of glaciated, montane catchments. Of particular concern are catchments in the Tien Shan and the Pamir Mountains in the areas, where glacial-fed rivers flow past major urban centres, and in the west of Central Asia near the Caspian and Aral Seas. Climate-change studies, which focus on Central Asia, consider mainly long-term changes in air temperature and precipitation, shrinking glaciers and physical hydrology, complex transboundary water management and policy issues. While, water quality (WQ) has received much less attention yet is noted as a potential issue primarily due to exposure of heavy metals and trace elements due to glacial retreat, release of aerosols deposited in snow and ice, and the dilution of pollutants from urban and farmed areas further downstream. To fill this knowledge gap the current project ‘Solutions to secure clean water in the glacier-fed catchments of Central Asia – what happens after the ice?’ established WQ monitoring program in four CA countries. The project aims to characterise and model, in a consistent and comparable way, the impacts of climate change and diminishing cryosphere on water availability and quality in the selected glacier-fed catchments informing environmental policies and adaptation strategies and building research capacity in the region. To this end WQ sampling and measurements were established in four glacier-fed alpine catchments on rivers passing major cities: Kishi and Ulken Almaty rivers (Kazakhstan, Almaty city), Ala-Archa River (Kyrgyzstan, Bishkek city), Chirchik River (Uzbekistan, Tashkent city), Varzob (Tajikistan, Dushanbe city). The WQ monitoring programme is based on bi-weekly sampling along river elevation profile from upstream (closer to glacierized area) to downstream (up to a reservoir or inflow to a major river). Groundwater (urban, artesian, springs), streamwater, reservoirs have been sampled and measured for temperature, electrical conductivity (EC), total dissolved solids (TDS), pH, nitrates, phosphates in situ and in the labs by local teams. These measurements are complemented by extended analysis for cations and anions during peak of steam flow (glacier and snow melt period) and low flow season in autumn (baseflow dominated). The preliminary results show that these catchments relatively clean with potentially toxic elements not exceeding WHO drinking water values in all monitored components. The dilution effect of glacier and snow melt on streamwater in summer is reflected in EC seasonal pattern. Primary concerns are elevated nitrate concentrations in urban groundwater in three studied catchments (Kyrgyzstan, Uzbekistan, and Tajikistan) with median values exceeding 10 mg/L of nitrate-N (a WHO’s drinking water guidelines threshold). The intermittent spikes of high phosphates in streamwater and groundwater in Uzbekistan in the autumn, in some cases reaching more than 4 mg/L (phosphate-P) are possibly linked to fertilizers wash-out by rainfall.