Abstract

Rapid change of alpine lakes in the Tibetan Plateau (TP) is a clear manifestation of regional-scale climate variability that can be investigated by quantifying the regional hydrological cycle. The degree-day model (DDM) coupled with the Soil and Water Assessment Tool (SWAT) model were used to quantify the water budget of the Nam Co Lake over the period of 2007 to 2013. Driven by local observed meteorological data, the coupled model was successfully validated with the observed lake levels (with R2 = 0.65, NSE = 0.61, and PBIAS = −2.26). Analysis of the water balance revealed that rapid enlargement of the Nam Co Lake was primarily associated with precipitation increase while glacier melt played its role as the potential secondary driver in lake expansion. However, temporal analysis of lake expansion displayed that supremacy of precipitation and glacier melt interchanged between the years. It was found that average annual relative contributions of the precipitation, including direct precipitation on the lake, and glacier melt to the lake were 57% (or 667 mm), and 43% (or 502 mm), respectively. Besides, it was observed that annual values of actual evapotranspiration (ET) from the lake, glaciated, and non-glaciated subbasins were 615 mm, 280 mm, and 234 mm respectively. The average annual glacier mass balance (GMB) of the Nam Co basin was −150.9 millimeter water equivalent (mm w.e.). The relatively high amount of glacier melt was a consequence of the substantial increase in annual temperature in the lake basin. This work is of importance for understanding the rapid water cycle in the TP under global warming. Moreover, this work will also be helpful in monitoring and sustaining the local ecosystem and infrastructure, which is under risk due to rapid lake expansion as a result of climate change in the TP.

Highlights

  • Mountains and highlands are ultra-sensitive to climate change and are regarded as the amplifiers of regional and global climate change [1,2,3]

  • This study provides detailed long term spatiotemporal study provides detailed long term spatiotemporal changes in water budget, Glacier Mass Balance (GMB), and relative input changes in water budget, GMB, and relative input of streamflow to Nam Co Lake (using the coupled of streamflow to Nam Co Lake at basin scale which was missing in the model) at basin scale which was missing in the past studies

  • Due to the distinct physiographic conditions, there is no influence of human activities on the Nam Co Lake and, changes in its water level there is no influence of human activities on the Nam Co Lake and, changes in its water are a good indicator of regional climate change [12]

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Summary

Introduction

Mountains and highlands are ultra-sensitive to climate change and are regarded as the amplifiers of regional and global climate change [1,2,3]. Water 2019, 11, 1383 fresh water and are a sensitive indicator of local or regional climate change [5,6]. Changes in the volumes of the lakes provide information about in situ variations in the meteorological elements such as precipitation, temperature, humidity, and solar radiation, while disturbance in the regional water resources provides an indication of climate change on a broader scale [8,9,10,11]. Understanding how climate change influences the lakes in the Tibetan Plateau is vital for sustainable management of regional water resources [12]

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