Climate change is causing diminished rainfall and snowpack, especially in America’s west, where the population is also growing. This has caused drought conditions, which impacts farmers especially. It has also heightened fire disasters, like the recent events in Los Angeles, and parched western US forests. To accommodate for less rainfall and less snowpack, western farmers and towns are increasingly reliant on groundwater, to the extent that half-to-most of the water supplies for many western farms and rural communities is coming from groundwater. This is causing the groundwater levels to drop. Now, many western groundwater tables are 250 feet to more than 350 feet down (see attached figure). The “groundwater table” is the upper surface of saturated water in the ground. Tables have dropped in nearly all southwestern groundwaters, along with many groundwaters in Texas, the western plains, and southern Missouri. Declining groundwater levels is making it more tenuous and more expensive for farmers to grow crops and for small towns to survive. Importantly, a farm planted with lush crops achieves far more carbon dioxide capture than a barren parched field, and this opportunity should be factored into all environmental impact studies.
How do we cope with drought in the US west? Let’s begin this conversation by considering how it is decided who gets what water. In states where there has been more water than people use, water is generally allocated by “Riparian” water rights: Basically, if a user borders a waterway, they can have access to that water. Most eastern states abide by riparian water rights. In some states, such as Pennsylvania where I live, that allocation is permitted through a state agency. Alternatively, most western states abide by “Prior Appropriation” water rights, where “first in use” dictates highest priority for continued use. States with perhaps the more rigorous Prior Appropriation doctrines include Colorado, New Mexico, Arizona, Wyoming, Utah, and Nevada. I am most familiar with the Prior Appropriation doctrine in Colorado, where I served as a water engineer. In Colorado, these priority dates and water appropriations are legally owned and rigorously established, as is land ownership. Several states have a hybrid Prior Appropriation/Riparian doctrine, including California, Nebraska, and Oklahoma.
To grow crops the way American farmers commonly do, the crops need an annual volume of water that amounts to three feet deep over the whole field. This water can be provided either by rain or by irrigation. Then, when an agricultural field is transformed into a residential development, the residences likewise use an annual volume of water that amounts to three feet deep over that same amount of area. But the difference is that 100 times as many residents typically populate that developed area as did when it was a farm. The implication of this is that when it comes to a vote on who gets what water, the hundred (or so) residents will always out-vote the one farmer. This inherent disparity has driven too much of the decision-making about who gets what water in states that have loosely-defined water rights. In states like California, where water rights are loosely-defined, the farmers can simply lose out to the cities, with little equitable compensation.
In contrast, when a state judiciously abides by Prior Appropriation water rights, such as Colorado does, farmers can get admirably compensated when selling their water rights. Indeed, farmers can sell their water rights for more money than they can sell their farmland which the water had irrigated. This farm-to-town transfer of water rights is the major new water source for burgeoning towns and cities in Colorado.
The Central Valley of California hosts the world’s best cropland, and it provides a third of America’s vegetables and two thirds of its fruits and nuts. However, with recent city growth and droughts, more and more water has been diverted to the California cities, leaving some farms high and dry. Increasingly, acres of fertile land in the Central Valley are left fallow, growing only sparse sage brush. Across the Central Valley, the groundwater table is dropping 2 inches per year (Liu et al. 2022) in a water-bearing aquifer that is 1000-4000 feet deep (Bertoldi et al. 1991). Importantly, a deeper water table corresponds to higher pumping costs and lower water quality. Meanwhile, even the California cities have limited water, and this shortfall has heightened the recent LA fires’ destruction.
An important southwest water source is the Colorado River, whose watershed includes seven states. A century ago, a Compact was agreed upon between its Upper Compact States (Colorado, Wyoming, Utah, and New Mexico) and its Lower Compact States (California, Arizona, and Nevada). These states agreed that the Upper Compact States would have the same “equal” share of Colorado River water, as would the Lower Compact States. This Compact included no mention of Mexico, Native American water rights, or wildlife water needs. Moreover, ever since this compact was established, the Colorado River water yield has been less than initially envisioned—in part due to evaporation from dammed lakes. In recent years, water yields have declined even further with climate change. This situation has created numerous disputes regarding what “equal” shares and “other’s” shares mean.
For a typical non-coastal city, fresh water is drawn from a river, treated, and then distributed to its citizens. Then the wastewater generated by those citizens is conveyed to a wastewater treatment plant. Next, the cleaned effluent from that plant is returned to the same river—at a point downstream from where the fresh water was first drawn. At this downstream point, it becomes diluted by the rainwater that also flows in that river. That rainwater plus effluent then provides the source water for the next city downstream. This draw and return approach proceeds city-to-city along the river. The net effect is that for cities located at the far downstream end of a river, some of its source water may have already passed through a dozen intestines. Thus, water reuse is nearly universal, although perhaps not readily recognized as such. Indeed, water reuse is ingrained into the water rights laws in Prior Appropriation states. In Colorado, the water right appropriation applies only to the “consumed” water that is not returned to the river. The amount of wastewater that is treated and returned to the river is not considered as “consumed.”
Over the past century, extensive water projects have been built to import water to Los Angeles: from the Colorado River, Owens Valley (east of the Sierras), and northern California. Extensive water projects have also brought Sierra Nevada water to the Bay Area. All of the wastewater that is generated within these huge cities is treated. But then nearly all the cleaned effluent from these treatment plants is merely wasted into the ocean. This treated effluent should not be wasted, because it is a tremendous resource, and needs to be recognized as such. The problem is, however, that by the time this wastewater reaches its ocean-front treatment plant, it is already downhill from all the city-land and farmland that it could otherwise be beneficially used on. Thus, any reuse of reclaimed effluent will require pumping it uphill, which costs money. So, unfortunately, one California coastal city after another has found it cheapest to just waste its valuable water effluent into the ocean. The net effect is that 5-8% of all America’s treated water effluent is wasted to the ocean from California cities. This constitutes a vast wasted resource that could have been helpful to many, if it had not been squandered. When considering the past half-century of data, we roughly calculate that the amount of California water effluent wasted each year to the oceans is about equal to the loss of stored groundwater each year in the Central Valley.
But this will soon change. The two largest water treatment and wastewater treatment entities in Los Angeles are both planning upgrades to their huge wastewater treatment plants, so that most or all of their treated effluent will be further processed to become a source for drinking water. In addition to customary biological treatment, these processes will also include reverse osmosis and advanced oxidation disinfection. These Los Angeles entities aim to build and start-up these treatment plants within the 2030’s. The reverse osmosis effluent from these plants will be injected into groundwater basins, and then extracted and treated in LA’s water treatment plants. From there, it will be conveyed as drinking water to the Los Angeles area. Decades of technology development and water quality reliability research have gone into rendering this reuse as a viable and secure opportunity.
This reuse will defray the need for Los Angeles to import fresh water from long distances. In turn, this will indirectly leave more of the otherwise-imported water available for the farmers, residents, and cities of California’s Central Valley and other Colorado River Compact states. We encourage San Diego and the Bay Area to also pursue treated effluent reuse that is targeted for providing a source for drinking water.
This added Reverse Osmosis treatment and reclaimed water transport will incur costs. But remember, getting fresh water from distant sources to Los Angeles, San Diego, and the Bay Area in the first place has involved massive pipelines, aqueducts and pumping.
America’s western population will continue to grow, and climate change may well continue to incur impact. But in the meantime, these water reuse innovations offer equitable and proactive means for overcoming the increased constraints that are imposed upon a finite freshwater supply.
The author, Fred S. Cannon, has served as a consulting water engineer for 10 years in Colorado, California, and Arizona. He served as Project Engineer for designing Los Angeles’ largest water treatment plant—the LADWP plant. This LADWP water treatment plant is being slated to process LA’s reclaimed reverse osmosis effluent. In Colorado, Dr. Cannon master-planned and designed numerous water systems and treatment plants. A third of all Coloradoans were his clients.
Dr. Cannon has also conducted 30 years of research that pertains to reusing water. Dr. Cannon grew in his Christian faith as a high schooler at the church of Dr. Richard Halverson in Bethesda, MD. Dr. Halverson later became the Chaplain of the US Senate. Dr. Cannon has remained steadfast in his Christian faith, recognizing that all persons deserve respect as Children of God. He has pursued Environmental Engineering, as an act of worshiping God, who created this miraculous universe, earth, life, and humanity. God sees this creation as very good, and God has given humans the wisdom and skills to preserve this miracle—so we must.
