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Annual Water Supply & Demand Assessment

The Annual Water Supply & Demand Assessment ("Annual Assessment") is a new State-mandated report due July 1, 2022 and every July 1st thereafter. The Annual Assessment provides an estimate of the gap between demand for water and actual supplies available each year. The specific metrics that the CCSD utilizes to assess supply availability are included below.

  1. Dry season start date
    --Santa Rosa: May 1, per the CCSD’s water license issued by the State Water Resources Control Board. The maximum amount allowed to be diverted from the Santa Rosa Creek aquifer during the dry season is 155.3 acre-feet.
    --San Simeon: The date of surface flow cessation at Palmer Flats, per the CCSD’s water license issued by the State Water Resources Control Board. The maximum amount allowed to be diverted from the San Simeon Creek aquifer during the dry season is 370 acre-feet.
     
  2. Rainfall totals
    --Rainfall data will be obtained from the County of San Luis Obispo’s Public Works Department. The two gauges associated with the CCSD service area are Rocky Butte and Santa Rosa at Main. Data from both gauges will be averaged and analyzed for the assessment.
     
  3. Groundwater levels
    --Groundwater levels are measured at a total of 31 well sites each month, but the critical well sites for the purpose of this assessment include the San Simeon Well Field production wells (SS1, SS2 and SS3), Santa Rosa Well 4, and the Windsor Bridge monitoring wells (WBE and WBW). When the water level at the Windsor Bridge wells falls below 3.0 feet above mean sea level, the CCSD will cease diversions from the Santa Rosa wells.
     
  4. 9P2/SS4 gradient
    --The 9P2/SS4 gradient is measured twice per month and represents the difference in groundwater elevation between monitoring wells 9P2, located at the CCSD wastewater percolation ponds, and monitoring well SS4, located just south-west of the San Simeon Well Field. A positive gradient means groundwater levels at the San Simeon Well Field are higher than groundwater levels at the percolation ponds. Conversely, a negative gradient indicates that groundwater levels at the percolation ponds are higher than at the well field, which could result in migration of impaired water from the percolation ponds and saltwater lagoon towards the freshwater aquifer beneath the well field. When the 9P2/SS4 gradient is measured at or below -0.9 for more than three months during the dry season, operation of the percolation ponds for wastewater disposal will cease.

Each spring, CCSD staff will prepare the Annual Assessment for presentation to the board of directors with a request that the board vote on the findings and appropriately trigger any recommendations for shortage response actions results from the assessment.

The Annual Assessment will be prepared as follows:

  1. Beginning April 1 of each year, the Utilities Department will gather and analyze key inputs and historical data to determine potential supply and demand gaps, as described within the WSCP. Water shortage evaluation criteria will be analyzed as a percent of normal with “normal” being represented as each metric’s average as of April 1st. If needed, the CCSD’s contract hydrogeologist will be consulted to validate assumptions about the conditions of the groundwater aquifer.
  2. No later than June 15, staff will present the findings of the Annual Assessment to the Board, including recommendations to adopt a specific water shortage stage, if warranted. Should the Board determine criteria have been met to declare a water shortage stage, it shall immediately consider adopting a resolution implementing the appropriate stage.
  3. The Annual Assessment is due to the Department of Water Resources each year, starting July 1, 2022.
  4. At least once per month during the dry season, or during implementation of any drought stage beyond stage 1, staff will provide an update to the Annual Assessment in the General Manager’s or Utilities’ Report. The update will include a brief comparison of the current percent of average for each water shortage indicator used in the report, along with any recommendation for movement within the stages.

 

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