Slowing the Water: Natural Infrastructure in the Dry Streams of Baja California Sur

The Los Planes watershed in Baja California Sur, Mexico, gets an average of just 28.1 centimeters of rain a year, and its population and farms keep needing more water. Its aquifer is declining, and with it comes the risk of desertification — soil and vegetation degrading until farmland turns to desert. One ranch there is trying a cheap, low-tech idea: small earthen structures in its dry stream channels that slow the water down.

What natural infrastructure in dryland streams does

Natural infrastructure in dryland streams (NIDS) — natural or human-made structures of earthen material — slows fast runoff so water can soak into the ground. The USGS has documented their benefits across the southwestern United States and northern Mexico:

• water infiltrates, building thick, rich soils that store atmospheric carbon and keep green growth going longer and over more ground;
• healthier plants and more water cool the air and surface through shade and evapotranspiration;
• vegetation stabilizes hillsides and cuts erosion and sediment movement;
• the result helps recharge aquifers and can reverse degradation and desertification, with low cost and low technology.

Sandbags and rock gabions used as natural infrastructure in a dryland stream. Image from the U.S. Geological Survey's fact sheet.

Another natural infrastructure structure in a Los Planes stream. Image from the U.S. Geological Survey's fact sheet.

The study

In 2022 the USGS began working with regional researchers and land managers to measure what the ranch's structures actually do. It uses a paired-watershed design: small watersheds within Los Planes serve as controls (without NIDS) or treatments (with them), so the effects on groundwater recharge, erosion, runoff and vegetation can be compared against a baseline.

• Instruments: meteorological stations and hydrologic monitors record precipitation, groundwater and surface water levels, and stream discharge; ranch wells are instrumented to track water levels.
• Underground: ground-penetrating radar maps the depth to bedrock, to understand how water moves into bedrock fractures.
• From above: remote sensing and field observations build a land-use map, estimate evapotranspiration and track vegetation.
• Models: the data calibrate surface and groundwater models of the water budget and of how NIDS change a watershed's response to rain.

Groundwater well monitoring by Jason Sorenson of the USGS and Carlos Lim of Innovaciones Alumbra helps set the parameters of a water budget. Image from the U.S. Geological Survey's fact sheet.

The objectives are to understand the area's hydrogeology, compare treated and untreated sites, and support local efforts to make water more available and communities more climate-resilient. Eight study tasks are meant to converge in a Center of Applied Dryland Water Studies for the region.

Teaching the watershed

In March 2024, the USGS and local partners — Kumutú STEAM, the Center for Renewable Energy and Environmental Quality, Agua Viva BCS and Pronatura Noroeste, with water-science students from the Autonomous University of Baja California Sur — held the Caminos del Agua Water Festival at the Los Girasoles community center in El Sargento. One hundred and fifteen middle and high school students rotated through hands-on activities on water quality, aquifer recharge, nature-based solutions such as NIDS, scientific methods, environmental health in virtual reality and water awareness. Earlier work had students building "do it yourself" rain gauges.

Sources

Based on "Preserving and increasing water resources—Natural infrastructure in dryland streams in Baja California Sur, Mexico," a USGS fact sheet by Alma Anides Morales, Laura M. Norman and Thomas J. Mack, a work of the United States government in the public domain. The research is supported by the U.S. Water Partnership and Innovaciones Alumbra; the fact sheet is also available in Spanish. The photographs are reproduced from the fact sheet.