Troubled Waters

The report highlights that California's water system is engineered for historical conditions that no longer apply due to climate change. It identifies critical shifts in the state's hydroclimate—including declining snowpack, more extreme precipitation events, and increased volatility between wet and dry years—that threaten the viability of surface reservoirs and groundwater aquifers. The authors argue that while the data to plan for these changes is available, state and local agencies are underprepared, often relying on outdated operational rules or proprietary models. The report recommends updating the Sustainable Groundwater Management Act (SGMA), developing new hydrologic operations models, and increasing collaboration between climate scientists and water managers to prevent wasted investments and exacerbate inequities between well-resourced and vulnerable communities.

• Climate change is fundamentally altering California's hydroclimate, with high model agreement on several critical shifts: precipitation is increasingly arriving as rain rather than snow, extreme events are becoming more intense, and the wet season is narrowing.
• Severe climate change is projected to significantly degrade snowpack health, effectively removing the natural snowpack reservoir as a reliable storage source, particularly at lower elevations.
• Increased precipitation volatility and extreme events create a 'whiplash' effect that stresses infrastructure and increases the risk of floods and mudslides, while not necessarily replenishing groundwater reservoirs.
• Current groundwater management under the Sustainable Groundwater Management Act (SGMA) is insufficient because it only suggests minimal consideration of climate shifts and does not require planning for climate extremes.
• There is a growing gap in climate adaptation capacity between wealthy regional water agencies, such as the Los Angeles Metropolitan Water District, and under-resourced rural communities that lack the means for sophisticated risk analysis.
• Analysis of the Lake Oroville reservoir shows that severe climate change would concentrate inflows into winter months, increasing outflows when demand is lowest and creating water deficits during the summer and fall.

APA

Union of Concerned Scientists (2020). Troubled Waters. https://www.ucs.org/sites/default/files/2020-10/troubled-waters.pdf

Chicago

Union of Concerned Scientists. Troubled Waters. 2020. https://www.ucs.org/sites/default/files/2020-10/troubled-waters.pdf.

Wikipedia

{{cite report |author=Union of Concerned Scientists |title=Troubled Waters |date=October 2020 |url=https://www.ucs.org/sites/default/files/2020-10/troubled-waters.pdf |access-date=23 October 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{unionofconcernedscientists2020troubled, author = {{Union of Concerned Scientists}}, title = {{Troubled Waters}}, institution = {Union of Concerned Scientists}, year = {2020}, month = oct, url = {https://www.ucs.org/sites/default/files/2020-10/troubled-waters.pdf}, urldate = {2026-10-23}, note = {Indexed by Climate Insights Directory} }