Groundwater Usage is Unsustainable

Supplemental Water Supply such as Desalination  Can Help Prevent Seawater Intrusion

For many years, groundwater levels in the Soquel Creek Water District (SqCWD) have been dropping and remain too low to protect against seawater intrusion. Despite extensive conservation efforts by customers, the Soquel-Aptos groundwater basin is in a state of overdraft because more water is being pumped out annually than is naturally recharged through rainfall. The groundwater basin is the SqCWD’s only source of water.

Overdraft of the groundwater basin is not sustainable and early signs of seawater intrusion are present in the La Selva Beach area and low groundwater levels are affecting SqCWD wells in the Aptos/Seacliff area. Seawater intrusion occurs when groundwater levels drop so low that wells become contaminated with seawater. This condition can be irreversible and can result in either abandoning wells or requiring costly treatment. In order to manage its groundwater basin, SqCWD needs a supplemental water supply to meet customers’ needs and raise groundwater levels to prevent seawater intrusion.

What is Seawater Intrusion?

As mentioned above, seawater intrusion is a condition whereby groundwater is withdrawn at a faster rate than it can be replenished by rainfall and seawater or ocean water moves into the freshwater aquifers. 

seawater intrusion

SqCWD's Integrated Resources Plan

The proposed desalination plant is consistent with the SqCWD’s Integrated Resources Plan (IRP), a flexible, phased approach for providing a reliable supply of water,  preserving coastal aquifers from seawater intrusion, and protecting public health and safety. The IRP’s preferred alternative identified maximizing conservation and further evaluation of a regional seawater desalination project with the City of Santa Cruz that can be used in conjunction with groundwater resources. The IRP includes the following components:

  • Conservation and Curtailment — Continue conservation and drought management programs to reduce water demand and increase water-use efficiency.
  • Supplemental Supply — Develop a regional desalination plant with the City of Santa Cruz to meet additional water needs.
  • Recycled Water — Develop site-specific recycled water supplies for non-potable irrigation use.
  • Groundwater Management — Continued monitoring and assessment of coastal groundwater quality and levels; redistribute groundwater pumping to alleviate the potential for seawater intrusion; and support aquifer recharge protection and enhancement.

Soquel Creek Water District's Two-fold Approach to a Sufficient Supplemental Supply

In order to assure a reliable water supply, SqCWD’s two-fold approach includes developing a sufficient supplemental supply to:

  1. Restore protective groundwater levels by limiting groundwater pumping. This could be as much as 35% (~500 million gallons/year) less than current pumping and may take 20 years or more before the basin recovers. Protective groundwater levels are the minimum needed to prevent seawater contamination as identified by the District’s hydrologist.
  2. Maintain protective groundwater levels for the long-term. Hydrologists predict that after the basin has recovered, groundwater pumping must be restricted by at least a quarter million gallons per year less than current use. Conservation alone will likely not save enough, and there will be an ongoing need to supplement our groundwater sources.

What if We Do Nothing?

If Soquel Creek Water District (SqCWD) were to take no action to develop a supplemental water supply, these consequences could occur:

  • The continued overdraft of the groundwater basin would lower groundwater levels and increase the risk of seawater contamination of SqCWD’s production wells.
  • Reduced pumping to the level needed to recover the groundwater basin would result in water restrictions for customers that could create hardships for residents and local businesses.
  • Restrictions on year-round water use for existing customers and a moratorium on new or expanded services could be imposed.
  • Reduced water sales due to restrictions would cause rates to increase in order to meet the fixed costs of delivery and maintenance of the water system
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