Satellite Laser Altimetry Reveals a Net Water Mass Gain in Global Lakes With Spatial Heterogeneity in the Early 21st Century

Lake water storage changes are important factors that influence the climate, hydrological cycle, and environments. However, long-term estimation of global lake storage changes is challenging because historical in-situ hydrological observations worldwide are rarely available. Benefiting from the laser altimeter ICESat and ICESat-2, we comprehensively assessed water level and volume changes in global natural lakes larger than 10 km(2) during 2003-2020. The 6,567 lakes observable by ICESat/ICESat-2, which account for similar to 94% of the total global lake volume, showed a total water storage increase of 10.88 +/- 16.45 Gt/yr during 2003-2020, and the estimate reaches 16.12 +/- 20.41 Gt/yr when also taking account of the remaining unobserved lakes. Despite water gains in most natural lakes, large lakes under dry and high water-stress conditions experienced dramatic water loss in general. Presumably, these drying lakes may continue to shrink with a warming climate and continuously increasing water demands in the future without further action. Plain Language Summary The development of satellite techniques allows monitoring long-term lake water storage changes in extended regions. Particularly, laser altimetry satellites (i.e., ICESat/ICESat-2) that provide high precision elevation data show the potential to estimate lake water level changes globally. Totally 6,567 global lakes were observed by the ICESat/ICESat-2, revealing a total lake water storage increase of 10.88 +/- 16.45 Gt/yr from 2003 to 2020. Assuming that lakes show similar changes in the same climate zone and basin, we extrapolated the estimates of water storage changes to the entirety of 14,705 natural lakes larger than 10 km(2) in the world. The water storage in these lakes globally increased at 16.12 +/- 20.41 Gt/yr during the past near-two decades. We found that lake changes are highly different in different climate zones and basins. Lakes in dry climate conditions shrank considerably and may continue to decline in the future.

Automated summary

Lake water storage changes play a crucial role in the climate, hydrological cycle, and environments. Using satellite data from ICESat and ICESat-2, researchers have studied the water level and volume changes in global natural lakes larger than 10 km(2) from 2003 to 2020. They found that, overall, the total water storage in these lakes increased during the studied period. However, large lakes under dry and high water-stress conditions experienced significant water loss. The findings suggest that these drying lakes may continue to shrink in the future due to climate change and increasing water demands.