Zero Flow Days

When streams that run into the Rio Grande run dry, they do not provide water to the river or water for the plants, animals, and human communities that depend on them.

Dry riverbed, by Audra Melton.

How is it measured?

Data from 48 USGS gauge stations were used to determine how many there was zero flow, or no flowing water, at gauge stations over the course of one year. If there were no zero flow days in a region, that region scored 100%. A failing score of 0% resulted if 25 or more zero flow days were identified.