Таац голын усны горимын судалгаа

Detecting changes to flow regime on the Taats river

Abstract

Surface water resources and flow regime of the river are dependent on climate, physical geography, soil condition, geology and hydrogeological conditions of the basin. These factors vary spatially and temporally and affect the runoff. To study the flow regime of the river including snowmelt and rainfall flow is crucial information for flood mitigation, control, water harvesting, hydro construction planning, dam and other hydrologic systems, etc.  Therefore, we attempted to investigate the flow regime and its changes of the Taats river which is located in the Asian internal drainage basin in this study. The study was conducted using the daily runoff, precipitation and air temperature data for the period of 1975-2019. In addition, the Mann-Kendall test was applied to detect trend analysis for the annual runoff and maximum flow of the snowmelt and rainfall events. The probability of the maximum runoff of the snowmelt was estimated through the Gringorten method. The results show that the mean annual runoff and snowmelt flow decreased and rainfall flow has increased insignificantly in the study period.  However, it was observed the changes in the timing of the snowmelt runoff shifted toward later in the year 1975-1990, earlier in the year 1991-2003 and on average in the period of 2004-2019. The maximum runoff of the snowmelt and rainfall is estimated at 13.2 m3/s and 275 м3/c, respectively in the 100 years.