[Mick]

San Luis Reservoir will soon expand by 130,000 acre feet, enough for 650k people for a year. Meaning they will raise the 382 foot dam walls by 10 feet.

Santa Clara Valley Water District will come up with slightly less than half of the funding ($435 mms.). Total cost, $942 mms.

Deal reached to expand massive reservoir near Bay Area to increase water supplies

Under the deal, the federal government will put up 30% of the funding and receive 30% of the new storage space in the reservoir, or 39,000 acre feet. The eight water agencies will contribute 70% of the funding and receive 91,000 acre feet [70%]. Construction would begin in 2027 and end in 2032, overseen by the Bureau of Reclamation.
...
Other agencies that would receive some of the water are the massive Westlands Water District in Fresno, the Byron Bethany Water District in Contra Costa County, the city of Tracy, the San Benito County Water District and the Del Puerto, San Luis and Pacheco water districts.

IIUC, this will increase the capacity by about 6.5%.  But the numbers given are for storage capacity, not flow.

How much of the current water (outflow) is earmarked for So.Cal. municipal systems,  Central Valley farmers?
Where does the 30% new capacity for the Federal Government go?

I don't quite understand how this works. Sure, it will hold more water when full.  But how much does S.C. County get each year?  Is there sufficient inflow to fill it each year?  It seems there has been in the last few years, but go back 3 years and it was about 100' lower than today.   If it isn't full, will S.C.C. get a proportional share, or will SoCal and the farmers get first dibs.

It seems this reservoir is managed to maintain a level of about 100' lower than the top of the dam.   In 2019, it was within 50' of its capacity only for 4.5 months.  The next year, only a month.  From May 2020 to March 2023, it never got within 50'.  From October 2023 to now, it hasn't been within 50' of capacity.    I kinda wonder what good the extra 10' will do.  If we get the rains/snow of 2023 each year, great.  But even those rains didn't help the reservoir for a year.

Has SCC already acquired the money for this?

It seems like a reasonable deal if SCC is guaranteed 6.5% * 60% of the outflow.

The San Luis Reservoir has been full three times over the past 12 years. It's located between Gilroy and Los Banos and is the fifth largest reservoir in the state. Eight separate water agencies reached a deal with the Federal government to increase the reservoir's size. Under the deal, the Santa Clara Valley Water District, a San Jose agency that provides water to 2 million residents in Santa Clara County, would contribute $435 million [46%] of the $942 million cost of the project. It would receive the largest share of the new water, 60,000 acre feet [46%].

Bing Videos

The extra 60,000 af are approximately three times the size of Lexington Reservoir. Fun fact: San Luis Reservoir is the largest off-stream reservoir in the United States. From Wikipedia: An off-stream reservoir is a reservoir that is not located on a streambed, and is supplied by a pipeline, aqueduct or an adjacent stream. San Luis Reservoir is the largest off-stream reservoir in the United States. Although it is located on a small stream, it gets the vast majority of its water from the California Aqueduct by pumping aqueduct water up-hill to the reservoir.

Deal reached to expand massive reservoir near Bay Area to increase water supplies | News & Features | ArcaMax Publishing

Deal to expand reservoir should boost California's water supply | KTVU FOX 2

Here's a photo of the reservoir from March 30, 2023:



And this photo is from September, 2024:

[Mick]

San Luis Reservoir will soon expand by 130,000 acre feet, enough for 650k people for a year. Meaning they will raise the 382 foot dam walls by 10 feet.

Santa Clara Valley Water District will come up with slightly less than half of the funding ($435 mms.). Total cost, $942 mms.

Deal reached to expand massive reservoir near Bay Area to increase water supplies

Under the deal, the federal government will put up 30% of the funding and receive 30% of the new storage space in the reservoir, or 39,000 acre feet. The eight water agencies will contribute 70% of the funding and receive 91,000 acre feet [70%]. Construction would begin in 2027 and end in 2032, overseen by the Bureau of Reclamation.
...
Other agencies that would receive some of the water are the massive Westlands Water District in Fresno, the Byron Bethany Water District in Contra Costa County, the city of Tracy, the San Benito County Water District and the Del Puerto, San Luis and Pacheco water districts.

IIUC, this will increase the capacity by about 6.5%.  But the numbers given are for storage capacity, not flow.

How much of the current water (outflow) is earmarked for So.Cal. municipal systems,  Central Valley farmers?
Where does the 30% new capacity for the Federal Government go?

I don't quite understand how this works. Sure, it will hold more water when full.  But how much does S.C. County get each year?  Is there sufficient inflow to fill it each year?  It seems there has been in the last few years, but go back 3 years and it was about 100' lower than today.   If it isn't full, will S.C.C. get a proportional share, or will SoCal and the farmers get first dibs.

It seems this reservoir is managed to maintain a level of about 100' lower than the top of the dam.   In 2019, it was within 50' of its capacity only for 4.5 months.  The next year, only a month.  From May 2020 to March 2023, it never got within 50'.  From October 2023 to now, it hasn't been within 50' of capacity.    I kinda wonder what good the extra 10' will do.  If we get the rains/snow of 2023 each year, great.  But even those rains didn't help the reservoir for a year.

Has SCC already acquired the money for this?

It seems like a reasonable deal if SCC is guaranteed 6.5% * 60% of the outflow.

The San Luis Reservoir has been full three times over the past 12 years. It's located between Gilroy and Los Banos and is the fifth largest reservoir in the state. Eight separate water agencies reached a deal with the Federal government to increase the reservoir's size. Under the deal, the Santa Clara Valley Water District, a San Jose agency that provides water to 2 million residents in Santa Clara County, would contribute $435 million [46%] of the $942 million cost of the project. It would receive the largest share of the new water, 60,000 acre feet [46%].

Bing Videos

The extra 60,000 af are approximately three times the size of Lexington Reservoir. Fun fact: San Luis Reservoir is the largest off-stream reservoir in the United States. From Wikipedia: An off-stream reservoir is a reservoir that is not located on a streambed, and is supplied by a pipeline, aqueduct or an adjacent stream. San Luis Reservoir is the largest off-stream reservoir in the United States. Although it is located on a small stream, it gets the vast majority of its water from the California Aqueduct by pumping aqueduct water up-hill to the reservoir.

Deal reached to expand massive reservoir near Bay Area to increase water supplies | News & Features | ArcaMax Publishing

Deal to expand reservoir should boost California's water supply | KTVU FOX 2

Here's a photo of the reservoir from March 30, 2023:



And this photo is from September, 2024: