Thirsty plants are depleting the Colorado River by drawing on groundwater, a new study shows. This finding has significant implications for water management in the region, which over 10% of the U.S. population relies on.
Scientists previously thought plants used shallow soil moisture from recent rain or snow, which would reduce evapotranspiration in dry conditions. However, researchers at Princeton University discovered that plants maintain or even increase transpiration during droughts, tapping into groundwater.
The study, conducted in the East River watershed, found that even in hot, dry summers, evapotranspiration remained high. Plants were using water that would otherwise end up in the river, leading to reduced streamflow.
Summer temperatures have a significant impact on streamflow, regardless of winter snowfall. Over the past century, temperatures in the Colorado River Basin have risen by 2.5 degrees Fahrenheit, and water flow has dropped by 35% in the last seven years. This could lead to a 40% decline in water availability by mid-century.
These findings highlight the need for better water management and recalibration of water budgets in the face of rising temperatures and declining river flows.