Runoff dynamics of the upper Selenge basin, a major water source for Lake Baikal, under a warming climate

Abstract

The Selenge basin contributes approximately 50% of the total inflow into Lake Baikal and is thus of high significance for the regional hydrological regime. Our study was conducted in the upper reaches of the basin, where the Selenge river and its tributaries flow through the Mongolian forest-steppe. Monthly and maximum runoff, precipitation, and air temperature data from 12 gauging stations collected between 1978 and 2015 were analyzed to characterize the hydrological regime response to climate change. Concomitant with rising temperatures and increased potential evaporation, river runoff in the Mongolian part of the Selenge basin has decreased from the first interval (1978)(1979)(1980)(1981)(1982)(1983)(1984)(1985)(1986)(1987)(1988)(1989)(1990)(1991)(1992)(1993)(1994)(1995) of our study period compared with the consecutive interval from 1996 to 2015. The decrease in runoff throughout the study area was most likely caused by an increase in potential evapotranspiration (and not reduced precipitation or land use changes) for both summer rainfall-and snowmelt-dominated rivers. Annual maximum runoff has also strongly decreased suggesting that reduced flooding is a contemporary threat for Mongolia's riverine ecosystems, probably causing the replacement of wetland and mesic habitats.

Human impact and ecosystemic health at Lake Baikal

“…Rising temperatures could encourage evaporation of inflowing waterways before they reach the lake. Historical data from monitoring sites along the Selenga showed a negative correlation between temperature and river runoff (Zorigt et al, 2019). And wildfires can be expected to increase with aridity due to changes in global pressure systems (Safronov, 2020).…”

Long-Term Response of Floodplain Meadow Normalized Difference Vegetation Index to Hydro-Climate and Grazing Pressure: Tamir River Plains, Mongolia

“…This is because the meadow vegetation grows rapidly throughout the summer due to the abundance of water, nutrient enrichment, warm temperatures, and species adaptations. However, variations in water flow, both within and between years [32], and the reduced maximum water flow of the main rivers in the Selenge basin in Mongolia could potentially result in the degradation of wetlands and moist habitats [33]. Tserendash and Bilegt [31] reported a decrease in the number of plant species and pasture productivity in the Selenge basin meadows over the past few decades.…”

“…We examined NDVI fluctuations at two meadow sites adjacent to the Tamir River system every sixth year between 1991 and 2015. Given the noted decrease in runoff in the Selenge basin's main rivers since the mid-1990s [33] and the ongoing rise in livestock numbers, our study sought to test the following hypotheses. Hypothesis (1): Floodplain meadows experienced a decrease in NDVI from 1991 to 2015 due to reduced moisture levels and increased grazing pressure.…”

Climate Change Impact On Flood Runoff Over Lake Baikal Catchment

“…Also, there is a lack of quantitative estimates of the particular climatic drivers impacts on abrupt changes in water delivery to Lake Baikal. Some studies showed importance of evaporation in ow decline (Sinyukovich and Chernyshov 2019b;Zorigt et al 2019) but some stress the importance of precipitation (Frolova et al 2017). Furthermore, it is remains unclear what cause evaporation change in BC on a basin scale (Minderlein and Menzel 2014).…”