How the Delta Conveyance Project Would Make California's Water Supply More Resilient Against Earthquakes

Operations Update

Following the April 20, 2023, announcement that State Water Project (SWP) allocations to state water contractors, such as SGVMWD, were being increased to 100% of plan for the first time since 2006, the benefits have continued to flow to the Main San Gabriel Basin and our member cities. The increase means the District will be allocated 28,800 acre-feet of imported water in 2023 to deliver and use for replenishment of groundwater in the Main San Gabriel Basin.

We are working closely with state and county water agencies to utilize available capacity in reservoirs, pipelines and spreading grounds to deliver the imported water. With water delivery capacity “overflowing” due to the abundance of stormwater runoff and snow melt throughout the state, scheduling deliveries is complicated and requires smart water management. Some of the 2023 water deliveries will likely need to carry over into the next calendar year.

In August, the District delivered 2,113 acre-feet (AF) of water to cyclic storage and 860 AF to CIC on behalf of Three Valleys Municipal Water District. Three important facility maintenance projects are underway: the Hydro 24-inch Butterfly Valve Replacement Project is nearly completed, and contract documents have been submitted to the contractors for both the San Gabriel Flow Control Structure 30-inch Ball Valve Replacement Project and Schedule I Pipeline Continuity Bonding and Corrosion Assessment Validation Project. On May 15th, the District began generating power at its San Dimas Hydroelectric Facility for the City of Azusa. Power generation in August was 182.4 MWh. 

Imported water supplements local groundwater supplies in the Main San Gabriel Basin, the primary sources of water for the District’s member cities of Alhambra, Azusa, Monterey Park, and Sierra Madre. The planned allocation may be adjusted in the future based on hydrological conditions.

The continuation of the snowmelt and ensuing water runoff in August, coupled with increased flow of imported water into the San Gabriel Valley, precipitation created by Tropical Storm Hilary, and aggressive stormwater capture infrastructure and programs, further improved drought and water supply conditions statewide and the Valley. Smart water management and collaboration between water agencies is needed to strategically time releases of water in reservoirs into nearby streams and spreading grounds. 

The graphics above show the marked improvement from January through September 2023 in state and local reservoir, snowpack and groundwater conditions, including significant lessening of drought conditions statewide. Local groundwater, which improves more slowly due to the time it takes stormwater runoff to percolate down to groundwater levels, has risen more than 50 feet year-to-date!

The Main San Gabriel Basin captured more than 95% of stormwater to supplement local groundwater supplies in the storm surge earlier this year, which is much different than other watersheds that convey the majority of their stormwater to the Pacific Ocean as a flood control measure. Data from Watermaster reveal that of the more than 500,000 acre-feet of stormwater captured this year, about 300,000 AF came from the San Gabriel River watershed.

While Mother Nature has granted us a reprieve from the most recent drought, we must remember we live in a region where most years are dry, infrastructure is aging, drought will return, and climate change makes the work of water planning and delivery challenging. The reality remains that we use more water than Mother Nature provides and if we’re not in a drought, we are probably either getting into one or recovering from one. 

We need to sustain our focus on investments in long-term water infrastructure and developing a long-term water conservation ethic that enables us to save water now, when it’s wet, for when it’s dry. While the State and some municipalities have lifted certain water use restrictions, it’s important to note that in the past 1-2 years Californians fell short of meeting the voluntary 15% conservation goal and also fell short of the 25% conservation level achieved in the next most recent drought period. 

Groundwater – in the Main San Gabriel Basin, the “Baldwin Park Key Well” is the indicator of local groundwater levels (see graph – blue line includes cyclic storage; black line does not). As of September 1, 2023, the level decreased slightly to 227.4 feet above mean sea level (see most recent Baldwin Park Key Well below).

Prior to the storms earlier this year, the Basin had experienced a steady decline in groundwater levels from a high of 212.5 feet above mean sea level in December 2019 and was trending downward toward the historic low of 169.4 recorded on November 21, 2018. One vertical foot is equivalent to about 8,000 acre-feet of groundwater in the Main Basin. Watermaster’s operating guidelines for replacement water or “safe yield” is between 200 and 250 feet above mean sea level. 

About 80 percent of the Valley’s water supply is furnished by local groundwater, and the Valley imports about 20 percent of the water we use from northern California and the Colorado River. A 60 percent allocation is needed to meet the demand of our member cities for replacement water. Thus, in years where the allocation dips below that amount, we see the important role that water storage and water conservation play.

Note: Groundwater use accounts for 41% of California’s total water supply (80% in the San Gabriel Valley) on an average, annual basis, and as much as 58% in a critically dry year. About 85% of public water systems rely on groundwater as their primary supply. Of water diverted and pumped in California, about 80% is used by agriculture and 20% is used by cities and towns.

Imported Water – In April, the California Department of Water Resources increased State Water Project allocations to State Water Contractors such as SGVMWD for 2023 to 100% for the first time since 2006. Imported water is used to supplement local groundwater supplies in the Main San Gabriel Basin.

Note: Two-thirds of California’s water originates in the Sierra Nevada Mountains and flows through the Delta, a large inland river delta and estuary in northern California.

Statewide Snow Pack – as of September 1, the State is reporting 0% for its snow data, effectively starting its recordings anew as we head into the fall and winter months. Snowpack is measured from April 1 to March 31, a 12-month period). April 1 is usually the “high point” for snow accumulation each year. What remains of the recent winter’s snowpack is one of the biggest the state has experienced since the 1950s.

Note: On average, the Sierra Nevada Mountains snowpack, which is a key source of water banked in reservoirs, supplies about 30% of California’s water needs as it melts in the spring and early summer, feeding reservoirs and the water table, resulting in groundwater. The snowpack is often referred to as California’s “frozen reservoir.”

Statewide Reservoir Levels – statewide, as of July 30, 2023, (the latest statewide data available to us), reservoir levels had risen to 125% of average and 83% of capacity. As of September 1, storage levels at Shasta Lake, the state’s largest reservoir, were 77% of capacity and 129% of the historical average for this date, and storage levels at Lake Oroville, the state’s second largest reservoir, were 80% of capacity and 138% of the historical average. 

Locally, both San Gabriel Reservoir and Cogswell Reservoir are conducting sediment removal, and Lake Silverwood, which rests above San Bernardino and is adjacent to the start of the District’s Devil Canyon-Azusa Pipeline, is filled to 87% of capacity and 98% of average. During the recent drought, low precipitation levels, high temperatures, hot and dry soil, and high levels of evaporation decreased stormwater runoff from surface levels to replenish both reservoirs and local groundwater supplies.

Note: Every winter, most areas need about 12 inches of rainfall before the ground is saturated enough to get large amounts of runoff into streams and reservoirs. California’s reservoirs generally hold enough water to go one dry year without impacts but begin to empty if a wet year does not follow.

Hispanic Heritage Month in Monterey Park

For the upcoming Hispanic Heritage Month, The City of Monterey Park will be celebrating with various events and activities which include a Movies in the Park cosponsored by the District. Join us with the City of Monterey Park on Thursday, September 21, 2023 at 6:30pm for the showing of Selena at Barnes Park. Check the City of Monterey Park's website for more details.