California’s weather whiplash has left the Golden State in a place of severe uncertainty about its diminishing water supply and increasing human and environmental demands for water.
Research that my colleagues and I published last year, “The Magnitude of California’s Water Challenges” showed that Californians can expect their water supply to shrink 12 to 25% by 2050, up to 9 million acre-feet, or equal to one to two Lake Shastas.
Our recent follow-up research, “Inaction’s Economic Cost for California’s Water Supply Challenges” (insert link once available) estimates the costs of such water supply losses. These economic losses could reach $3.4–6.4 billion per year in a likely future or $7.0–14.5 billion in a worse scenario, with up to 67,000 jobs statewide.
Four main factors explain our ongoing loss of water supply. The largest is the ending of groundwater overdraft under California’s Sustainable Groundwater Management Act, particularly for the state’s largest agriculture regions. Second, climate change will increase statewide evaporation and shrink the seasonal build-up of snowpack that our water system relies on. Third, our natural environment—facing the decline of many native species, water-quality perils, and climate changes—will need more robust flows. And fourth, Colorado River supplies will be further reduced, even for California’s senior water rights.
Inaction at the state and regional levels, without better management and infrastructure, creates economic risks statewide, especially for California’s rural and agricultural communities. Across these regions, 12 to 25% less water available annually, permanently fallowing 1.5 to 3 million acres of farmland, or 17 to 35% California’s current irrigated farmland. Even with most crop losses being felt by lower-priced crops this would destroy some local economies.
However, the inevitable overall reductions in water supply and their economic consequences could be significantly offset with careful new sources of supply and water use reductions.
The development of potential new sources, like new and improved above- and below-ground storage and conveyance infrastructure, stormwater capture facilities, wastewater recycling plants, desalination plants, and more, will require collective, coordinated action by state and regional policymakers and stakeholders.
The costs for most new water supplies are steep, since we have already build water infrastructure at most of California’s least expensive and higher yield locations. So economically, most supply losses will likely be covered with reduced water use, including some greater use efficiency. But water conservation measures alone cannot economically recover all supply losses.
Water conservation dilemmas are increased because urban water use, where conservation most often occurs, accounts for only 10% of all water used in the state. Substantial urban water conservation has offset most urban growth in California for several decades. Further urban conservation, while valuable, becomes increasingly expensive with diminishing water yield and cannot solve the state’s water woes alone. Agricultural water use reductions will be greater because it uses four times the water as urban areas and produces less than 5% of California’s overall economy, despite sizable growth from shifts to permanent crops. There will be many cases where increases in supply will be less expensive than reducing high-valued agricultural and urban uses.
Planning for these reductions—and coordinating the federal, state, regional, and local authorities involved in water supply—requires a unifying framework. It often makes sense for individual projects to develop under regional and local leadership; but overall direction for an issue as fundamental and vital as California’s water supply often requires state-level, big picture leadership.
Proposed legislation, SB 72, authored by Sen. Anna Caballero of Merced (author of last session’s SB 366), is one of several efforts to increase state leadership in organizing state and regional stakeholders to come together to plan for more secure and reliable water supplies statewide. This bill would set a long-term target of 9 million acre-feet of additional statewide water supply by 2040, reflecting recent California efforts to set and promote targets for housing, energy, transportation, and education.
The future will depend on California’s statewide, regional, and local leadership to work together to balance decreasing water supplies with increasing demands for water. The state is uniquely qualified to establish a framework for such cooperation. Water conflicts are inevitable in dry California, but such conflicts with deteriorating ecosystems and climate conditions will be far more expensive and frustrating without state leadership and facilitation.
Jay Lund and Alvar Escriva-Bou are professors of Civil and Environmental Engineering at the University of California – Davis and Josue Medellin-Azuara is a professor of Civil and Environmental Engineering at the University of California – Merced.