Simulation of river flow in the Gunt River Basin in Tajikistan

Mountainous regions of the world are the source of water for large amount of population living downstream. This is also the case for Pamir Mountains in Tajikistan which produces majority of the water for the several countries in the region. Despite increasing impacts of climate change, last several decades, there have been critical decrease of number of monitoring networks in mountainous areas of Central Asia bringing high uncertainty to water resources management and planning. In this study we investigate the possibility to combine the remote sensing data, ground observations and a modelling approach to estimate discharge of Gunt River in the Eastern Pamir, Tajikistan. The Gunt River watershed is of great importance for the region, as about 60 settlements are concentrated along the entire length of the river, including the administrative city of Khorog. Two hydropower stations were built in the lower reaches of the river to provide electricity for the local communities. These headwater glacier-fed basins of Central Asia are particularly vulnerable; as climate change threatens water supply from glacier systems and increases evaporative losses, while demand to irrigation water and electricity is rising. This uncertainty in water supply can result, to a deterioration in the development of the economy and the quality of life in the region. Therefore, for sustainable electricity production and economic development in the region, a better understanding of water availability in the river, is required.

 

The aim of the study is to assess the characteristics of the flow regime of the Gunt River. We used "Hydrograph" hydrological model to simulate daily discharge of the Gunt River. The model algorithms combine physically based and conceptual approaches to describe snow and glacier melting and runoff generation processes. "Hydrograph" model has also successfully used to simulate river flow in Varzob River with similar climatic conditions in Tajikistan. Parametrization of the model including the assessment of precipitation distribution in the high mountainous areas is based on the data from the research watershed of the Varzob River with long term historical data availability. The verification and evaluation of the model was conducted based on the historical data (1970-1980) using data from the Dzhavshangoz and Khorog meteorological stations. The model performance and simulations for the recent period (2000-2020) were also evaluated by using the remote sensing data. The results have shown satisfactory quality with difference between the observed and simulated runoff does not exceed 2%. In general, the results of the paper confirm the possibility of using the deterministic model "Hydrograph" to simulate the daily water runoff in the river which is critical for hydropower and irrigation purposes. However, the lack of accurate information on distribution of precipitation in the catchment, significantly reduces the model results accuracy. The study was carried out with the support of St. Petersburg State University (project 75295879).