California is on the brink of a water crisis, with projections showing a potential decrease in water availability by 4.6 to 9 million acre-feet yearly. Despite conservation efforts, scarcity is inevitable, according to a new report titled “The Magnitude of California’s Water Challenges.”
Commissioned by the California Municipal Utilities Association and written by Jay Lund at UC Davis, Josue Medellín-Azuara at UC Merced, and Alvar Escriva-Bou with UCLA, the report outlines the state’s water management issues and predicts future water losses. These estimates aim to guide public policy and investment choices in addressing California’s pressing water concerns.
Water use trends
Over the past 150 years, California’s water policy has focused on developing infrastructure and institutions to provide water for economic and population growth. As the economy shifted from mining to agriculture to manufacturing and ultimately to providing services, the economy has become less dependent on abundant water supplies. Today, roughly 95% of California’s population and economy are urban and supported by approximately 20% of California’s human water use. The urban economy, primarily service-oriented, is not driven by water abundance, and per-capita water use in urban areas has diminished.
However, most rural areas depend on domestic wells and small water systems and face water quality, affordability, and supply problems. Small water systems are often out of compliance with drinking water standards, and domestic wells are polluted with one or more contaminants. Many domestic wells have dried up from declining groundwater levels. These problems disproportionately burden poor communities of color in the San Joaquin Valley and elsewhere. The state is working to address these problems through the Safe and Affordable Funding for Equity and Resilience (SAFER) program.
The report summarizes potential changes in water use for each sector:
- Urban water use: Urban water use includes residential, commercial, industrial, and institutional usage in cities and rural areas. With current per capita urban use and population projections, total urban water use is unlikely to grow at the pace of the last century. Improvements in water use efficiency and conservation policies will likely drive further reductions in total urban water use, perhaps by a further 10-20%, depending on population growth.
- Agricultural water use: Agricultural water use is predominantly water used for irrigation from both surface and groundwater sources. Changes in crop evapotranspiration from a changing climate will affect agricultural water demands by increasing demands by 5 to 10% in dry years. This increased irrigation demand will likely increase overall scarcity.
- Environmental water use: Environmental uses include water for instream flow requirements, managed wetlands, required Delta outflow, and wild and scenic river flows. Regulations, such as water quality regulations and standards for salinity control, are likely to continue and accelerate to improve or maintain ecosystem health. However, higher temperatures, longer summers, more evapotranspiration, and diminishing snowpack are making conditions less suitable for many of the state’s native species. Sustaining native and desirable ecosystems will likely require more water and other resources.
Water supply losses
California faces increasing water scarcity due to climate change, the implementation of SGMA, and the challenges of long-term drought on the Colorado River. The reduction in water availability in the coming decades could range from 4.6 to 9 MAF per year, equivalent to roughly 3 million acres of irrigated agriculture or most urban water use. Conservation and water supply improvements could address about 20-30% of the shortages, leaving a 3 – 7.2 MAF per year average difference between statewide water demands and availability.
These losses include:
- Ending groundwater overdraft under SGMA will eliminate 2-3 million acre-feet/year of unsustainable groundwater pumping.
- Reduced Colorado River supply to California is needed to stabilize reservoirs and improve the sustainability of Colorado River basin water supplies; 1.5-2.5 maf/year will likely be needed.
- Climate change will increase evaporation and evapotranspiration (ET) from watersheds and crops, reduce snowpack, raise sea levels affecting Delta exports, and cause more intense atmospheric rivers and other changes. These seem likely to average between 1-3 maf/year, even with some reoperation of water systems. This will increase the state’s already high surface water supply variability, challenging flood and drought management.
- Increased environmental flows for Bay-Delta outflows and other streams seem inevitable to comply with environmental laws and regulations and will likely total 1-2 maf/year.
- Other supply losses: In the coming decades, the salination of some aquifers will render them less useful, particularly in the Tulare basin. Impairment of water supplies from nitrate or other pollutants also may reduce the availability of safe drinking water where treatment costs are prohibitive. Land subsidence from groundwater pumping has reduced canal conveyance capacities in the southern Central Valley and might reduce the ability to capture water in the wetter years. New infrastructure can provide some additional water supplies and efficiencies in existing water uses but is unlikely to supply enough to eliminate all water scarcity in most years.
Conclusions
Among the conclusions, the report points out that California will always have water challenges. California’s water infrastructure, technologies, and institutions also need to adapt.
Water supply problems vary considerably across the state, and fortunately, California has a diverse portfolio of options to manage these challenges. However, important water problems remain for all sectors, with the most significant challenges for ecosystems, rural drinking water supplies, and agriculture.
Recent droughts have exposed the growing limitations of California’s water system. Droughts exacerbate water scarcity and its impacts far beyond average scarcity conditions. Adapting infrastructure, institutions, and preparations to manage droughts potentially more extreme than those seen historically, along with more intense precipitation events, will be vital for maintaining public health, prosperity, and ecosystems through the inevitable droughts.
Some water scarcity is unavoidable for California, as eradicating it completely would come at a high economic and environmental cost. By tailoring actions to changing conditions, California can reduce the impact of water scarcity within sustainable levels and enhance the state’s resilience to climate change. The report notes that a certain level of scarcity can actually benefit water users and managers by fostering innovation and maintaining focus.
The report concludes, “With prudent and deliberate actions, most, but not all, water uses can be reliably supported while keeping a thriving economy. Good management and policy for this situation requires organized serious attention, without complacency or panic.”
