February 16, 2022 359 PM
In the last issue of “Our Water Matters,” we looked at the revival of ancient water canals in Peru to sembrar el agua (plant the water), a technique that directs mountain streams underground during the rainy season to enhance the water supply during the dry season.
Our own desert environment here in the Big Bend is also subject to wet and dry seasons, with most of our rain falling within the span of a few months or even weeks during the North American monsoon. This water percolates down through stream bottoms and rock to ultimately replenish or “recharge” the aquifers beneath us. We can then pump this water out of our wells or utilize spring flows and subirrigated pastures (verdant meadows with a high groundwater table that provides natural irrigation), enabling us to live comfortably in the arid Chihuahuan Desert.
As our dry seasons get longer, hotter, and drier, we will need to maximize this recharge by making the most of the water when it falls. Many natural systems, including streams, creeks, and draws, have traditionally acted as sponges to hold this rainwater, allowing it to slowly infiltrate into the ground and in some places, the aquifer. But, according to Jeff Bennett, a local restoration hydrologist, many of these systems have been degraded over time and no longer function as they once did. “Folks think this is normal,” says Bennett. But “it’s not how it used to be.”
Under Bennett’s direction, Rio Grande Joint Venture (a public-private partnership working to conserve birds and their habitats in the U.S. and Mexico) is currently restoring some of the region’s Rio Grande tributary streams using “low-tech ideas based on ancient technologies that you can find on every continent.” One approach involves driving posts into a streambed and filling them in with brush to create so-called “brush weirs.” Another involves piling rocks across incised waterways to form loose structures that also act as filter dams. Both types of structures slow water and naturally trap seed and sediment as water passes through them during rain events. According to Bennett, this preserves “resources that are otherwise washed away” and promotes revegetation and restoration of “riparian” areas (the land along rivers and creeks). The goal is to “build a bigger and better riparian sponge” that can absorb and store water that will increase resilience to drought by lengthening the time during which the creeks actually run.
With the help of these filter dams, degraded streambeds fill in with sediment and vegetation, spreading the flow of water over the land during rain events and allowing more of it to soak into the floodplain and recharge the underlying aquifer. Bennett urges people to “envision a local aquifer under a stream like a water glass.” Once the glass is filled, normal stream flows can move on downstream and eventually reach the Rio Grande, albeit over a longer period. In addition to a longer wet season, water quality is improved as the water soaks into the flood plain and is more slowly released. Healthy streams also improve forage for cattle and wildlife, promote more woody vegetation that shades the streams and decreases evaporation, and provides better bird and wildlife habitat.
Bennett works for the Rio Grande Joint Venture, a public-private partnership among Migratory Bird Joint Ventures (MBJVs), which were established in response to declining waterfowl populations in the 1980s. MBJVs proved successful in contributing to a rebound in waterfowl populations. The Rio Grande Joint Venture is one of eight joint ventures focused on grasslands and grassland birds, which are experiencing steep declines in much of their ranges. He and his colleagues found that “what’s good for the bird is good for the herd.” Wide open grasslands interlaced with healthy streams are the preferred habitat not only of some birds, but also pronghorn and cattle. Restoring our streams and riparian areas could go a long way to increasing the quality and quantity of the water that reaches our aquifers and improving the value of the land. Bennett is constantly working to expand these efforts and is always looking for “willing landowners” to participate.
For more information visit the Rio Grande Joint Venture website at rgjv.org or call Jeff Bennett directly at 432.837.7335.
Trey Gerfers is a San Antonio native and serves as board chairman of the Presidio County Underground Water Conservation District. He earns his living as a translator of technical documents from German to English for the German and Swiss pharmaceutical and medical-science industries. Trey has lived in Marfa since 2013. He can be reached at [email protected]