The Owens Lake Dust Mitigation Program is the largest dust mitigation project in the United States. While originally constructed to meet dust control requirements, the Owens Lake Dust Mitigation Program is currently managed in collaboration with multiple partners to meet goals for dust emissions, managing habitat value, protecting cultural resources, and other public trust values while using water efficiently.
Since the early 2000s, LADWP has been funding and implementing the program, successfully reducing dust emissions by 99.2 percent, utilizing approved dust control methods or best available control methods (BACMs) which include Shallow Flooding, Managed Vegetation, Gravel, Tillage with Shallow-Flooding Backup, and Brine with Shallow-Flooding backup.
Best Available Control Methods
LADWP has installed one of the world’s largest shallow flooding systems, consisting of a vast network of computer-controlled valves, pipes, outfalls, and sprinklers placed across the ancient lakebed. Shallow Flooding prevents dust emissions by applying water to emissive playa surfaces, suppressing windborne dust. Currently, it is the predominant dust control method on Owens Lake, making up approximately 30 square miles of the Program area. In order to meet the requirements for dust control within Shallow Flooding Dust control areas, 72% - 75% of the graded surface must be maintained as wet or have saturated soil during the dust season, between mid-October and early July. The presence of standing water eliminates dust generation from the wetted surface and also traps blowing sand that enters the ponded area.
Brine with Shallow Flooding
Owens Lake is primarily a salt lake with a large brine pool at its center. Brine with shallow flood Backup is utilized in Shallow Flood Dust Control Areas where salinity levels are high enough to create a salt crust to effectively keep dust emissions down. In these areas, about 75% of the surface must be covered with a combination of evaporite salt crust, capillary salt crust, and/or saturated surfaces. The liquid brine serves in the same manner as the shallow flooding, eliminating any sand or dust sources as well as capturing saltating particles. The evaporite crust that forms subaqueously from the evaporation of standing brine, serves as the armoring of the surface to reduce dust emissions. This crust is primarily evaporite minerals (solid-phase salts as well as the potential for interstitial brines) and is not easily eroded by wind. Capillary brine crust, termed from its formation during the capillary rise of shallow brine in the sediments, forms from the evaporation of shallow groundwater, precipitating salts both within and on top of the lake sediments (GBUAPCD, 2016b). There are numerous saline shallow flood areas that are unable to meet the brine crust compliance criteria and, as a result, continue to be operated as shallow flood areas, using freshwater to meet cover compliance by wetting the surface. Similarly, if crust within a brine area breaks down, it is flooded to meet shallow flood wetness criteria, hence the term “back-up.” The stunning reds that paint these brine areas and the brine pool are attributed to salt-loving halobacteria.
Gravel cover is a zero-water-use DCM that involves distributing a layer of gravel on an emissive lakebed to protect it from the wind. Gravel protects the bare ground underneath it against wind erosion by substantially reducing the capillary rise of saline groundwater and salt and crust formation. Some areas are covered by 4 inches of gravel, while others are covered by 2 inches, underlain with a permanent permeable geotextile fabric to prevent settling of the gravel. The gravel, which is mined and transported to the site, is required to be of similar color to that of the lakebed soils. The geotextile fabric is a 2.3-mm thick (90 mils) artificial fabric that is permeable to draining and resistant to acids and alkali elements of the soils. To protect the gravel-covered area from flooding, channels and drains are incorporated into the area surrounding the control area.
Tillage with Shallow Flooding Back Up
Tillage is a widely used method for wind erosion control in agricultural and arid regions around the world. It works by roughening the soil surface, rendering it resistant to wind erosion. Tillage also reduces the wind speed at the surface by shear stress partitioning and the creation of turbulent eddies. The roughened surface also provides traps to catch windblown soil particles. Installed tillage is composed of rows and furrows in roughly east to west directions to create maximum surface roughness against high winds predominantly from the north and south. Where existing infrastructure has allowed, tillage has been installed in a serpentine pattern to provide additional protection from all wind directions. If the regulatory erosion threshold or any of the tillage performance requirements are no longer met, maintenance is performed to restore roughness, or Shallow Flooding is implemented as a backup control method.
Managed vegetation on the playa is an effective means to prevent and reduce dust as it decreases both sand motion and soil erosion. In physical terms, the aboveground vegetation acts as a windbreak, which lowers wind velocity at the playa surface and consequentially reduces the sand movement that leads to PM10 generation. Vegetation cover must, on average, have 37% cover across a dust control area, meet levels of uniformity in vegetation distribution for multi-scale grid tests, and be composed of pre-approved, locally adapted, native plants.
Owens Lake Science Advisory Panel
Established within the 2014 agreement, the Owens Lake Scientific Advisory Panel (OLSAP) reviews scientific issues relating to controlling dust using waterless and low-water use methods, among other related matters. Staffed by the National Academy of Sciences, the panel provides advice on the reduction of airborne dust in the Owens Valley in California.
In 2020, the OLSAP published a consensus study report on the Effectiveness and Impacts of Dust Control Measures for Owens Lake.
Water Management at Owens Lake
There are approximately 48.6 square miles of dust control infrastructure spread across the 110 square mile lakebed with operations requiring approximately 60,000 Acre-ft of water annually. That makes Owens Lake the size of Sacramento with enough water used to supply the entire City of Long Beach. As regional and State water supplies continue to be stressed by climate change and drought, Owens Lake policymakers and scientists have concluded to sustainably move forward, dust mitigation must conserve water to the greatest extent possible while maintaining habitat and protecting cultural resources.