San Diego sits in a semi-arid climate and gets only about ten inches of rain in a typical year along the coast. There is no large river, and no mountain snowpack within reach. For most of the region’s history, the answer to that problem was to bring water from somewhere else. That history shapes the way water is managed in the county today, and it explains why the region has spent decades trying to depend less on any single source.
How did San Diego come to import its water?
The region’s first big step toward imported supplies came in the 1940s, when the San Diego County Water Authority was formed to bring water from the Colorado River through an aqueduct built by the Metropolitan Water District of Southern California. In later decades, the region also began to receive water from Northern California through the State Water Project, which carries Sierra snowmelt south through canals and pipelines.
Both systems have the same weakness. San Diego is at the end of a very long pipeline, and what arrives depends on snowpack hundreds of miles away, on court rulings and agreements among states, and on pumps and canals that can be disrupted by drought or earthquakes. The Water Authority has described the region’s goal in simple terms: do not rely on one source.
What is the mix today?
Water agencies report the supply mix in percentages, and the figures vary by year with weather and demand. In a recent breakdown from the Water Authority, roughly 61 percent of the region’s supply came from the Colorado River, about a third from local sources, and about 6 percent from the State Water Project. Local sources include desalinated seawater, recycled water, purified water and brackish groundwater. A decade earlier, the Water Authority’s own presentations showed local supplies at about 15 percent and the State Water Project at 17 percent, so the mix has changed considerably.
The categories help explain the strategy:
- Colorado River water, secured through long-term transfer agreements, is the largest share.
- State Water Project water, bought through the Metropolitan Water District, has shrunk as a share of the total.
- Local supplies, a mix of desalination, recycling and groundwater, are the growth area.
What are the Colorado River transfers?
In 2003, California water agencies signed the Quantification Settlement Agreement, which set out how the state would live within its Colorado River allotment and cleared the way for water to be transferred from farms in the Imperial Valley to urban areas. Under agreements tied to that settlement, the San Diego region obtained conserved Colorado River water, giving it a supply that is contractually its own and not simply part of the Metropolitan Water District’s pool.
The water still has to travel. The Water Authority moves it through pipelines controlled by the Metropolitan Water District, which means paying for conveyance and relying on a partner’s system. The Colorado River itself is under pressure from decades of drought and from demand in seven states, and the rules for sharing it among the states and Mexico are periodically renegotiated. Developments in those negotiations affect everything downstream, including San Diego.
What does the Carlsbad desalination plant add?
The Claude “Bud” Lewis Carlsbad Desalination Plant began producing water in 2015, supplying a share of the county’s water, estimated at roughly ten percent. Desalination takes seawater and removes the salt using reverse osmosis. It is more energy-intensive than most other sources and generally costs more per unit, but it is not tied to rainfall, so it supplies a dependable base in dry years. Environmental concerns include the plant’s intake and brine discharge, which regulators have addressed through permit conditions, and that dimension connects to the role of coastal regulators described in what the California Coastal Commission does.
What is Pure Water San Diego?
The City of San Diego runs its own water system, separate from the Water Authority, which sells wholesale water to the city and to more than twenty other member agencies. The city’s major local project is Pure Water San Diego, a program to treat recycled water to drinking-water standards. The city has said its goal is to produce more than 40 percent of its supply locally by 2035 through the program.
The idea of drinking purified recycled water gives some people pause, but the process is regulated by the state and involves multiple treatment steps, including advanced treatment like reverse osmosis and disinfection, before the water joins the supply. The project is large, expensive and takes years to build, with pipelines, treatment plants and a series of phases, and the city has funded it through a mix of ratepayer money, bonds, and state and federal loans and grants.
Who sets the prices residents pay?
A homeowner’s water bill passes through several layers. The Water Authority sells water to its member agencies, which include cities, water districts and a military base, and those agencies set rates for customers. The City of San Diego’s Public Utilities Department sets rates for city customers, and the City Council approves rate increases after notice and a public process, tied to the rules of California’s Proposition 218, which requires notice and the right to protest.
Several factors push rates up: the cost of imported water, the capital cost of local projects and the repair of aging pipes. At the same time, conservation has cut demand. Per-person water use in the region has fallen substantially compared with the early 1990s, and in dry years the region’s agencies have called for voluntary or mandatory cuts. Conservation rebates and turf replacement programs have been part of that effort.
How does this connect to the rest of the region?
Water is closely tied to land use and fire. Reservoirs in the backcountry feed the system, and watershed protection and wildfire planning are linked, a theme in wildfire preparedness in San Diego County. It also ties to the regional economy: biotech labs, farms and tourism all depend on reliable supplies, which is covered in the region’s economy.
What can residents do?
Individual choices matter at the margin. Replacing a thirsty lawn with plants suited to the climate, fixing leaks, using efficient irrigation controllers and watching for watering restrictions during dry spells all reduce demand, and rebates for some of those steps have been offered by local water agencies. Residents can also attend rate hearings and read the notices that accompany a proposed increase, because those documents explain what the extra revenue is meant to pay for. The cumulative effect of small reductions is part of why regional water use per person has fallen even as the population grew.
Where to check current numbers
Because supply mixes and rates change each year, the best sources are the San Diego County Water Authority’s annual reports and the City of San Diego Public Utilities Department’s urban water management plan, which sets out supplies and projected demand. The state’s Department of Water Resources publishes State Water Project allocations, and the U.S. Bureau of Reclamation reports on the Colorado River system. Those documents show the numbers that matter most: how much water is expected to be available, where it will come from, and what it will cost.
Sources: San Diego County Water Authority; City of San Diego Public Utilities Department; California Department of Water Resources; U.S. Bureau of Reclamation
