SYSTEMIC DYSTOPIAS GO GLOBAL

10631 (c) (1) Describe the reliability of the water supply and vulnerability to seasonal or climatic shortage, to the extent practicable, and provide data for each of the following:

(A) An average water year; (B) A single dry water year; (C) Multiple dry water years.

(2) For any water source that may not be available at a consistent level of use, given specific legal, environmental, water quality, or climatic factors, describe plans to supplement or replace that source with alternative sources or water demand management measures, to the extent practicable.

10635. Every urban water supplier shall include, as part of its urban water management plan, an assessment of the reliability of its water service to its customers during normal, dry, and multiple dry water years. This water supply and demand assessment shall compare the total water supply sources available to the water supplier with the total projected water use over the next 20 years, in five-year increments, for a normal water year, a single dry water year, and multiple dry water years. The water service reliability assessment shall be based upon the information compiled pursuant to Section 10631, including available data from state, regional, or local agency population projections within the service area of the urban water supplier.

5.1 Reliability of Supply

This section describes the reliability of each of COSMUD’s water supply sources that include:

 San Joaquin River Delta Water Supply

 Mokelumne River water from Woodbridge ID

 East San Joaquin Groundwater Basin

 Wholesale Supply from SEWD

A written description of the reliability of each supply will be presented, along with the average, single-dry, and multiple-dry water year scenarios. Finally the water supply will be compared to demand over the next 25 years for normal, dry, and multiple dry water years.

5.1.1 San Joaquin River Delta Water Supply

The San Joaquin River water supply that will be available when the DWSP WTP is completed in about February 2012 is projected to provide 30 MGD (33,600 AFY) on an annual basis. At this point COSMUD has not used water from this supply but COSMUD anticipates pumping restrictions to be in effect in the spring months to protect sensitive species. Even with pumping restrictions COSMUD anticipates being able to use the full 33,600 AFY allotment for normal, single dry, and multiple dry water year scenarios.

5.1.2 Mokelumne River water from Woodbridge Irrigation District

The current contract from Woodbridge Irrigation District (Woodbridge) is for an initial 6,500 AF/Y. This water supply is projected to be available in March of 2012 in conjunction with the

2010 City of Stockton Urban Water Management Plan Page 5-2 City of Stockton Municipal Utilities Department

completion of the DWSP WTP. The Woodbridge water will be conveyed to the new WTP for treatment and distribution. The plan for Woodbridge water is to be used when and if the San Joaquin River water pumping is curtailed. This supply will ensure the WTP will be able to meet the projected demand during the spring months. It is assumed at this time that the full supply will be available when it is needed.

Under this contract an additional 6,500 AFY WID supply will become available to the City as WID-served agricultural lands in the northern part of the City are annexed to the City for Municipal and Industrial (M&I) use at a rate of 3.0 AF/Ac/Yr.

5.1.3 East San Joaquin Groundwater Basin

Currently COSMUD relies on groundwater for their supply. Existing groundwater usage made up 42% in 2005 to 16% in 2010 of COSMUD’s supply. Groundwater usage has been decreasing steadily in the last 5 years and is projected to decrease to approximately 2,000 AFY when the DWSP WTP comes online. COSMUD still needs the groundwater supply to meet peak demands, maintain system pressure, and provide emergency water supply if other water supplies are curtailed.

As described in Section 4 the groundwater basin has historically been in overdraft and encountered water quality issues from salt water intrusion. M&I use historically make up about 6% of the total water extracted from the groundwater basin and the remainder being used for agricultural purposes. It is estimated, based on historical use and availability that 23,114 AF will be available for the normal, dry, and multiple-dry year scenarios to 2035. This estimate is based on the City’s overlying groundwater right of 0.6 AF per acre per year and the City’s current water service area acreage.

5.1.4 Wholesale Supply from Stockton East Water District

SEWD currently supplies the COSMUD with 74% of their water supply. SEWD provides treated water from New Hogan Reservoir, New Melones Reservoir, groundwater, and/or OID/SSJID transfers. More detail on their supply sources can be found in Section 2. The majority of SEWD’s water used for their urban retailers is diverted from New Hogan and New Melones Reservoirs. By contract, SEWD is required to deliver a minimum of approximately 20,000 AFY of treated water to the urban retailers (COSMUD and Cal Water). The minimum delivery is split between the urban retailers based on that year’s agreement on allocation. Historically SEWD has delivered as little as 12,495 AFY in 1990.

With COSMUD bringing the DWSP WTP online in about February of 2012, COSMUD is projecting to decrease the amount of SEWD water deliveries from about 74% of their total supply to approximately 50% of their total supply, or approximately 17,500 AFY. COSMUD is projecting to keep SEWD deliveries at this level for the projections presented in this UWMP.

Since SEWD has diversified its supplies with the SSJID transfer water, their supply of 17,500 AFY is projected to be 100% reliable for the normal and single dry year scenario. However, SEWD is forecasting a shortage for the multiple dry year scenario. Assuming COSMUD’s supply is 17,500 AFY or 40% of their firm supply of 44,000 AFY (excluding OID/SSJID and groundwater bank supply). The next three year minimum and multiple dry year supply is as follows:

2010 City of Stockton Urban Water Management Plan Page 5-3 City of Stockton Municipal Utilities Department

 Year 1: 17,500 AFY

 Year 2: 11,930 AFY (40% of 30,000 AFY)

 Year 3: 8,000 AFY (40% of 20,000 AFY)

This scenario is the most conservative supply for COSMUD from SEWD since the SSJID transfer water that is still in negotiation between SEWD, the Urban Contractors, and SSJID.

5.2 Summary of Supply Reliability

From the previous descriptions Table 24 has been developed to demonstrate the reliability of the existing supply under the normal year, single dry year and multiple dry year scenarios at year 2035. As can be seen in Table 24, SEWD is the only supply with any reductions under the multiple dry water year scenario. It is assumed that the deficit in supply from SEWD will be made up by using groundwater.

Table 24: Normal, Single, and Multiple Dry Year Supply Reliability at 2035 (AFY)

Multiple Dry Years Normal Year Single Dry

Year Year 1 Year 2 Year 3 Surface Water Supply (SEWD) 17,500 17,500 17,500 11,930 8,000 Surface Water Supply (DWSP) 33,600 33,600 33,600 33,600 33,600

Woodbridge ID 13,000 13,000 13,000 13,000 13,000

Groundwater Supply 23,114 23,114 23,114 23,114 23,114

Recycled Water 0 0 0 0 0

Total Supply 87,214 87,214 87,214 81,644 77,714

% Reduction 0% 0% 0% 6% 11%

5.3 Supply and Demand Comparisons

As shown on Tables 25, 26, and 27 below, this section compares water demands developed in Section 2 to the reliability of the supply. The comparison is required for the normal year, single dry year and multiple dry year scenarios in 5 year increments for the next 25 years. As previously discussed, the only reliability issue is the surface water supply form SEWD, then only for the multiple dry year situations. Water supply shortages in surface water will be made up from additional groundwater pumping.

2010 City of Stockton Urban Water Management Plan Page 5-4 City of Stockton Municipal Utilities Department

Table 25: Normal Year Supply and Demand Comparison (AFY)

2005 2010 2015 2020 2025 2030 2035 Supply totals 35,568 35,255 80,714 80,714 87,214 87,214 87,214 Demand totals 35,568 35,255 40,317 43,900 47,342 50,799 54,032 Difference (supply

Table 26: Single Dry Year Supply and Demand Comparison (AFY)

2005 2010 2015 2020 2025 2030 2035 Supply totals 35,568 35,255 80,714 80,714 87,214 87,214 87,214 Demand totals 35,568 35,255 40,317 43,900 47,342 50,799 54,032 Difference (supply

Table 27: Multiple Dry Year Supply and Demand Comparison (AFY)

Year Supply Demand Difference

Difference as

2010 City of Stockton Urban Water Management Plan Page 5-5 City of Stockton Municipal Utilities Department

5.4 Water Quality

This section describes the water quality of COSMUD’s supplies and the effects of water quality on the reliability of those supplies. Since COSMUD has a variety of supplies, each source will be discussed separately. Within the 25 year projection period water quality is not projected to affect supplies. COSMUD’s decision to provide most of its water from surface water from the San Joaquin River and treated water from SEWD will help ensure a high quality source of water.

By reducing groundwater usage, COSMUD will be able to use the groundwater as a high quality source during critically dry years when the surface water supplies are curtailed.

5.4.1 Groundwater

The City currently operates twenty-two (22) groundwater wells in North Stockton and five (5) groundwater wells in South Stockton. The quality of the groundwater has generally been good, with chlorination being the only treatment required. However, there are naturally occurring constituents in the groundwater such as arsenic and magnesium. The City has indicated that there is adequate groundwater supply that meets Title 22 requirements to meet groundwater usage projections.

5.4.2 San Joaquin and Mokelumne River Water

The DWSP treatment plant will be treating both San Joaquin River raw water and Woodbridge ID supplied Mokelumne raw water. The new treatment plant uses filtration and disinfection to remove solids, organic mater, and biological constitutions that are common in surface water supplies. There are currently no water quality issues that are projected to affect these surface water supplies.

5.4.3 SEWD Treated Water

The SEWD supply provided to COSMUD is a treated water supply. SEWD does not project any water quality issues affecting their supply.

5.5 Resource Optimization

Section 10620 (f) of the Act asks urban water suppliers to evaluate water management tools and options to maximize water resources and minimize the need for imported water from other regions. COSMUD understands the limited nature of water supply in California and is committed to optimizing its available water resources. This commitment is demonstrated through COSMUD’s use of water management tools throughout its service area to promote the efficient use of water supplies from local sources, wherever feasible. Additionally, COSMUD has taken efforts to procure new water supplies that include the DWSP San Joaquin River water and Woodbridge ID Mokelumne River water sources. COSMUD is a regular participant in local water resources planning efforts through SAWS as well as development of a robust water conservation program.

COSMUD has implemented a robust water conservation program, deployed in its service area.

In an effort to expand the breadth of offered programs, COSMUD partners with wholesale suppliers, and other agencies that support water conservation programs through SAWS.

2010 City of Stockton Urban Water Management Plan Page 6-1 City of Stockton Municipal Utilities Department