One place that critically relies on groundwater is the Rio Grande/Rio Bravo (RGRB) river basin, which creates the border between southern Texas and Mexico. More than 16 million people in this region in both the US and Mexico depend on this resource; it accounts for 25% of the water that is used for irrigated agriculture and public supply in the basin.
Not just the people, but the local wildlife and the river itself also heavily rely on groundwater. In some stretches of the Rio Grande-Rio Bravo, such as the Big Bend region, more than 50% of the water that flows in the river comes from groundwater during the months when the river volumes get low. It’s also the main source of water for wetlands and springs, which are of critical importance for freshwater biodiversity and migratory bird conservation.
One of the main challenges to protecting groundwater is that it is, of course, underground. Groundwater levels are not easily monitored with the naked eye and so supplies can be unknowingly polluted or even overdrawn, meaning that more is taken out of the ground than can be sustainably replenished. Groundwater can be polluted by landfills, septic tanks, leaky underground gas tanks, and from overuse of fertilizers and pesticides.
The water in RGRB is critically endangered. Surface water in the basin is 150% overallocated and the basin’s groundwater resources are similarly overdrawn. The river itself has lost approximately 90% of its historic flows and has been declared one of the 10 most endangered rivers, nationally. Climate change and rapid population growth in border cities are putting increasing pressure on the river’s precious resources.
However, groundwater has the ability to be recharged and replenished. It can happen naturally when rain and snowmelt seeps down into the cracks and crevices beneath the land's surface, or artificially when people take action to restore groundwater levels by redirecting water so it will be reabsorbed into the ground through canals, basins, or ponds.
