water-scarcity

What Is Brackish Water, and Why Does It Matter for Utah? Brackish water occupies the salinity range between freshwater and seawater—typically 1,000 to 10,000 parts per million (ppm) total dissolved solids (TDS), compared to less than 500 ppm for drinking water and 35,000 ppm for ocean water. It is too salty to drink or irrigate with, but far less salty than the ocean. And there is an enormous amount of it sitting beneath the Western United States. The U.S. Geological Survey (USGS) published a landmark assessment of the nation’s brackish groundwater resources, identifying brackish aquifers in 41 states. The total volume is staggering: an estimated 800 times the amount of fresh groundwater pumped in the United States each year. For a region locked in a multi-decade megadrought, this represents a resource that has been almost entirely overlooked. Utah is particularly well-positioned. The state contains extensive brackish groundwater formations in the Great Basin, the Uinta Basin, the Sevier Desert, and along portions of the Wasatch Front. These aquifers contain water with TDS levels ranging from 1,000 to over 35,000 ppm, with large volumes in the treatable 1,500–5,000 ppm range that is ideal for reverse osmosis desalination. How Severe Is Utah’s Water Challenge? Utah is the second-driest state in the nation by average annual precipitation, receiving just 13.2 inches per year according to the Western Regional Climate Center. Despite this, Utah has one of the highest per-capita water consumption rates in the country—approximately 220 gallons per person per day for residential use alone, roughly double the national average. The math does not work indefinitely. Utah’s population, currently around 3.4 million, is projected to reach 5.4 million by 2060 according to the Kem C. Gardner Policy Institute at the University of Utah. That growth, combined with declining snowpack and the ongoing crisis at the Great Salt Lake, is forcing a fundamental rethinking of the state’s water portfolio. The Great Salt Lake has declined to historically low levels, losing roughly two-thirds of its water since the late 1980s. The exposed lakebed contains heavy metals including arsenic and mercury, which become airborne dust during wind events, posing a public health risk to the Wasatch Front’s 2.5 million residents. The state legislature has responded with emergency water conservation measures, but conservation alone cannot close the supply-demand gap. Brackish desalination offers something that conservation, water transfers, and cloud seeding cannot: a new source of supply. And unlike seawater desalination, it does not require building pipelines to the coast. Where Are Utah’s Brackish Groundwater Resources? USGS mapping has identified several significant brackish aquifer systems in Utah: The Great Basin Aquifer System Covering much of western Utah, the Great Basin contains extensive basin-fill aquifers with brackish water at relatively shallow depths. TDS concentrations typically range from 1,000 to 10,000 ppm, with some areas exceeding 35,000 ppm near the Great Salt Lake. Communities in Tooele County, Millard County, and Box Elder County sit directly above accessible brackish formations. The Uinta Basin Northeastern Utah’s Uinta Basin contains brackish water associated with both the basin-fill aquifer system and deeper formations connected to oil and gas producing zones. Water quality varies widely, with TDS from 2,000 to over 20,000 ppm. The significant produced water volumes from the basin’s energy operations also represent a potential feed source for desalination. The Wasatch Front Along the urbanized corridor from Ogden to Provo, deeper aquifer zones contain brackish water beneath the shallow freshwater aquifers that currently supply much of the region’s groundwater. As freshwater aquifer levels decline, brackish desalination of these deeper zones becomes an increasingly practical supplement to existing supply. The Sevier Desert Central Utah’s Sevier Desert region contains substantial brackish groundwater resources. Several agricultural communities in this area already face water quality challenges from rising salinity in their existing wells, making desalination treatment a near-term necessity regardless of new supply development. What Does Brackish Desalination Cost Compared to Alternatives? Cost is where brackish desalination makes its strongest case. Because brackish water has significantly lower salinity than seawater, it requires far less energy to desalinate. Lower operating pressure means smaller pumps, less energy, and longer membrane life. Water Source Cost per Acre-Foot Energy (kWh/acre-foot) Practical for Utah? Brackish groundwater desalination $357–$782 800–2,600 Yes—local resource, proven technology Seawater desalination $1,000–$2,500 4,000–6,500 No—Utah is landlocked, pipeline costs prohibitive Colorado River (current allocation) $150–$400 Variable Limited—allocations fully subscribed, declining flows Long-distance pipeline transfer $1,200–$3,000+ 2,000–5,000 (pumping) Possible but extremely expensive and politically complex Agricultural water rights transfer $500–$2,000+ N/A Yes, but limited volume and socioeconomic impacts The Bureau of Reclamation’s desalination cost data, drawn from its research program funding 31 projects totaling $29 million, consistently shows brackish desalination as one of the lowest-cost options for developing new water supply in the inland Western states. When compared to the full lifecycle cost of long-distance water transfers or new reservoir construction, brackish desalination is highly competitive. How Does Brackish RO Technology Work? The core technology is reverse osmosis, the same membrane-based separation process used in seawater desalination but operating under significantly different conditions. Operating Pressure and Energy Brackish RO systems typically operate at 100–300 psi, compared to 800–1,200 psi for seawater systems. This pressure difference translates directly to energy savings. Specific energy consumption for brackish RO ranges from 0.5 to 2.5 kWh per cubic meter of product water, compared to 3.0–5.0 kWh/m³ for seawater RO (with energy recovery). For a municipal-scale brackish desalination plant producing 1 million gallons per day (MGD), annual energy costs at $0.08/kWh would be approximately $55,000–$275,000. The same volume from seawater desalination would cost $330,000–$700,000 in energy alone. Recovery Rates Brackish RO systems achieve higher water recovery rates than seawater systems—typically 75–90% compared to 40–50% for seawater. This means less concentrate (brine) to manage, which is a significant advantage for inland facilities where ocean discharge is not an option. High-recovery brackish systems using interstage chemical treatment or concentrate recycling can push recovery to 90–95%, minimizing the volume of concentrate requiring disposal. Membrane Selection Brackish water RO membranes are formulated differently than seawater membranes. They use thinner