EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

The decreasing Chlorophyll-a in Tibet Plateau lakes during 1986–2021 based on Landsat image inversion and their impact causes

Liping Zhu, Shuyu Pang, Chong Liu, and Jianting Ju
Liping Zhu et al.
  • Institute of Tibetan Plateau Research CAS, China (

Lake chlorophyll-a (Chl-a) is one of the important components of the lake ecosystem. The Chl-a concentration of global water has generally increased in recent decades due to climate change and intensified anthropogenic activity. However, few researches have been done on the lake Chl-a variations in remote areas with less disturbance by human activities such as the Tibet Plateau (TP). Here, we combined 95 in situ measured lake Chl-a concentration data and Landsat reflection spectrum to establish an inversion model of Chl-a concentration through the backpropagation (BP) neural network prediction method, by which the mean annual Chl-a concentration in the past 35 years (1986–2021) of 318 lakes with an area of > 10 km2 in the TP have been retrieved. Meteorological and hydrological data, measured water quality parameters and glacier change in the lake basin were used to elucidate the driving factors of the Chl-a concentration changes in the TP lakes, with the help of geographic information system (GIS) technology and by spatial statistical analysis. The results showed that the mean annual Chl-a in the 318 lakes performed overall decrease during 1986-2021, but 63%, 32% and 5% of the total number exhibited no significant change, significant decrease and significant increase, respectively. After a slight increase during 1986–1995 (0.05 μg/L/y), the mean annual lake Chl-a significantly decreased during 1995–2004 (–0.18 μg/L/y). Further, after a slight increase during 2004–2011 (0.07 μg/L/y), it decreased slightly during 2011–2021 (–0.04 μg/L/y). The mean annual lake Chl-a concentration was significantly negatively correlated with precipitation (R2 = 0.48, P < 0.01), air temperature (R2= 0.31, P < 0.01), lake surface water temperature (LSWT) (R2 = 0.51, P < 0.01), lake area (R2= 0.42, P < 0.01) and lake water volume change (R2 = 0.77, P < 0.01). The decrease in mean annual Chl-a was in consistant to the decrease in that of salinity (R2= 0.69, P < 0.01) and increase in that of transparency (R2= 0.55, P < 0.01). The Chl-a concentrations of non-glacial meltwater-fed lakes were higher than those of glacial meltwater-fed lakes, except during higher precipitation period. Our result of lake Chl-a inversion and their variation reason analyses is able to further deeply understand the climate change impacts on Chl-a changes in the TP lakes.

How to cite: Zhu, L., Pang, S., Liu, C., and Ju, J.: The decreasing Chlorophyll-a in Tibet Plateau lakes during 1986–2021 based on Landsat image inversion and their impact causes, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-6888,, 2023.