Science Source

Assessing recent declines in Upper Rio Grande runoff efficiency from a paleoclimate perspective

States that, since the 1980s, major river basins in the American Southwest such as the Rio Grande have experienced droughts, declining streamflow, and increasing temperatures
States that the runoff ratio—the portion of precipitation that ends up in the river each year, rather than evaporating—has been decreasing as well
Presents a new reconstruction of runoff ratio for the Upper Rio Grande basin back to 1571 C.E., which provides evidence that the declining trend in runoff ratio from the 1980s to present day is unprecedented in context of the last 445 years
States that high temperatures (together with precipitation) have an important influence, making very low runoff ratios 2.5–3 times more likely
These findings suggest that runoff ratio could decrease further if warming in the region continues, which may present challenges for water management in the river basin