Research shows that terrestrial water storage has declined significantly in the early 21st century. This loss in freshwater stores is mainly due to rising temperatures on land and in the oceans which are linked to an increased global incidence of drought. The projected warming of the planet indicates that this trend is unlikely to change any time soon. The decline in soil moisture in particular has been noted as being particularly stark and worrisome due to its link to drought.
The methods used to assess terrestrial water loss from 2000 to 2020 covered different aspects such as satellite gravity observations over land, satellite assessments of soil moisture, measurements of global sea level rise, and observations of variations in Earth’s rotation. The data agrees on one fundamental point – there has been a sharp decrease in water storage on land. From 2005 to 2015, the terrestrial water storage decreased by nearly 1.3 trillion metric tons, equivalent to a global sea level rise of 3.5 millimeters.
The decline in soil moisture has shown a significant loss, contributing to sea level rise in past years. This loss ultimately affects the water supply to ecosystems and the agricultural sector. Rising temperatures in the atmosphere and oceans have caused changes in precipitation patterns and intensified evaporation and transpiration, leading to a decrease in water infiltration into the soil. More water vapor from evaporation and transpiration can result in brief intense rainfall, with much of the water becoming runoff that flows to the sea.
The increase in demand for groundwater also contributes to the decline in water storage. Many researchers working on water-related issues are unaware of the connections between groundwater pumping and sea level rise. These changes are measurable and can affect the Earth’s axis tilt. The interconnectedness between different aspects of the water cycle is crucial for understanding the impact of human activities on water resources and the environment.
The total amount of water in Earth’s soils has been decreasing since the beginning of the 21st century, and with future projections indicating continued temperature increases, it is unlikely that this water will be replenished. This finding highlights the importance of water conservation and sustainable water management practices. As climate modeler Benjamin Cook notes, water is essential for all life forms, and if there is not enough water available, it can lead to various challenges and problems for ecosystems, agriculture, and human populations. Therefore, addressing water scarcity and ensuring water security are critical priorities for the future.
