Drought Protection 

The City of Santa Cruz faces two major challenges in meeting its future water supply needs: making sure there is enough water for its customers during severe drought periods and protecting the habitat of endangered fish in the San Lorenzo River, Newell Creek, and North Coast streams. Each of these scenarios means less water in the City’s water system and emphasizes the need for a supplemental water supply.

Because the City relies almost entirely on water from rainfall and water stored in the Loch Lomond Reservoir, the system is vulnerable to water shortages during severe drought conditions.

In normal and wet years, when rainfall and runoff are normal to abundant, base flows in the coast and river sources are restored by winter rains. Storage in Loch Lomond Reservoir is typically replenished to full capacity with runoff from the Newell Creek watershed and water diverted from the San Lorenzo River at Felton. Under these weather conditions, the water supply system is capable of meeting the City’s annual water requirements. However, the system is highly vulnerable to shortage in below normal, dry, and drought years, when the San Lorenzo River and coast sources run low. In these year types, the system relies more heavily on water stored in Loch Lomond to satisfy demand, which draws down the reservoir level lower than usual and depletes available storage. In critically dry or multi-year drought conditions, the combination of very low surface flows in the coast and river sources and depleted storage in Loch Lomond reservoir reduces available supply to a level that cannot support even average dry season demands.

The City experienced severe water supply deficiencies in both the 1976-77 and 1987-92 droughts. In 1977, the City imposed severe water rationing in response to a critical shortage of water. During the 1987-92 drought, a water supply emergency was declared and either usage restrictions or rationing was imposed each year for five consecutive years. The 1976-77 event has since been established as the most severe drought of record, and is used by the City as a benchmark for assessing system reliability. If a critical drought similar to 1976-77 occurred today, shortages would be in excess of 40 percent.

Image illustrates the Annual Runoff, San Lorenzo River
where years in "RED" represent Critically Dry or Drought Years

Updating Demands

The City is currently updating information on water demands, supply reliability, water conservation measures, and water shortage contingency planning as part of the updates to the Urban Water Management Plan and the environmental review process for the proposed desalination project. This information will be incorporated into the Draft Environmental Impact Report (EIR) that is being developed for the proposed project.  Water shortages related to drought conditions with updated demand projections will be included in this evaluation.