Main San Gabriel Basin Watermaster

Main San Gabriel Basin Watermaster A governing body created in 1973 by the Superior Court of Los Angeles County to administer the Basin's adjudicated water rights and manager water resources

Watermaster was created in 1973 by the California Superior Court of Los Angeles County to administer the Basin's adjudicated water rights and to provide a basin-wide governing body for management of water resources. Beginning in the 1940s, the San Gabriel Valley experienced a period of rapid urbanization, which led to an increased demand for water drawn from the Main San Gabriel Basin. The ensuing

rise in water consumption--along with an extended period of drought--had, by the 1950s, put the Basin into a state of overdraft, where water production from the Basin exceeded the amount that could be replaced. As a result of the decrease in available water supply, parties downstream of the Basin became especially concerned. These downstream water users rely on the Main San Gabriel Basin for a large portion of their natural water supply, as much of it comes from the Basin by way of outflow through Whittier Narrows. Legal action was initiated on behalf of the downstream users, resulting in a court decision which requires the Upper Area (Main San Gabriel Basin) users to guarantee a source of water to the Lower Area or downstream users. For several years the Upper San Gabriel Valley Municipal Water District (Upper District) administered and took responsibility for the Upper Area's obligations to the Lower Area. The Upper District could not, however, assert control over all producers in the Basin because the district boundaries do not encompass the entire Basin. In 1968, at the request of producers, the Upper District filed a complaint that would adjudicate water rights in the Basin and would bring all Basin producers under control of one governing body. The final result was the entry of the Main San Gabriel Basin Judgment in 1973.

Applications for the Director of Water Resources position close this Friday, Nov. 14th! Lead critical initiatives that s...
11/10/2025

Applications for the Director of Water Resources position close this Friday, Nov. 14th! Lead critical initiatives that shape the future of sustainable water management- apply today! visit www.watermaster.org/careers

Hello! As the Executive Officer and Chair of our Board, we are thrilled to share the story of ourgroundwater. It connect...
05/22/2025

Hello! As the Executive Officer and Chair of our Board, we are thrilled to share the story of ourgroundwater. It connects 1.5 million of us in the San Gabriel Valley. Today, we are highlighting thework of nine people who govern our agency. Their quest is to ensure our groundwater is being wellmanaged. Every month, our board hears from experts about policy and legal needs, groundwaterlevels, and rainfall and snow levels to date. With that information, our Board together makesimportant decisions—like setting our OSY (see previous post). Our Board’s work is just another waythat for our groundwater, our care is constant.


Spring, Summer, Winter and Fall, what’s better than a warm cup of coffee in the morning? It’s havingit among colleagues ...
05/22/2025

Spring, Summer, Winter and Fall, what’s better than a warm cup of coffee in the morning? It’s havingit among colleagues and solving big challenges to our water supply together. Every quarter wecoordinate a meeting with the Main San Gabriel Valley Water Association’s 64 members—includingthe 25 water districts that provide the groundwater that connects 1.5 million of us in this amazingvalley. In our May springtime meeting, we’ll get an update about total rain and snow fall to date totrack our drought recovery and preparedness, announce this next fiscal year’s operating safe yield(check out the big story of OSY we shared last week), and hear from experts about more ways we cantake care of the waters that connect us. This quarterly coordination together is another one of theways that for our groundwater, our care is constant.


To celebrate Water Awareness Month, we’re highlighting throughout May what we do yearly,quarterly, monthly and daily bec...
05/22/2025

To celebrate Water Awareness Month, we’re highlighting throughout May what we do yearly,quarterly, monthly and daily because for our groundwater, our care is constant. Today, we’re sharingthe big story of three letters that every year guide us in how we care for our groundwater—OSY. Theystand for Operating Safe Yield. That’s the limit we set for how much groundwater can be withdrawnfrom our groundwater basin without taking out more water than it may get. Each May we set an OSYfor the next fiscal year. Just yesterday, we set it for the new fiscal year that begins this July 1 with anamount that translates into enough water for about 300,000 families for a year. Throughout the year,we’ll measure our groundwater levels to track how we’re doing. That’s the big story of those threeletters—OSY.


04/22/2025

This Earth Day we’re sharing the story about three natural elements related to our groundwater—sun, rain and snow. The sunny, dry conditions that we’re known for also put stress on our groundwater and the natural earthen basin that holds it. As it’s only getting sunnier and drier, these conditions create a constant drought cycle, so our care of our water needs to be constant, too. That care brings us to two water sources—our rain and snow. There’s nothing like the sound of a gentle rain or the sight of snow-capped mountains, but like most years for us, rainfall is below average so far this year. So when we have wet conditions, our aim is to capture rainfall and snow melt with local stormwater systems to hold these water sources in dams and reservoirs until they can be released into spreading grounds where they make their journey back into our groundwater. Sun, rain or snow, we work together in all types of weather. To learn more about the story of groundwater, please visit: thewatersthatconnectus.org and watermaster.org.


Much needed rain is falling here in our San Gabriel Valley this national Groundwater Awareness Week. Most of the rain th...
03/13/2025

Much needed rain is falling here in our San Gabriel Valley this national Groundwater Awareness Week. Most of the rain that falls will—with time—become part of our groundwater’s supply, helping
it recover from multiple droughts in the past decade. Just like it will take time and collective effort for our communities to recover from tragic fires, our groundwater and earth’s natural basin that holds
it needs rain, time and all of us for it to recover from a series of droughts and prepare for drought to come. Our groundwater: it’s our common ground and common cause. We all have a role in its care.

Since our last post, our extended Los Angeles community has been through devastating, tragic fires. Although our immedia...
03/10/2025

Since our last post, our extended Los Angeles community has been through devastating, tragic fires. Although our immediate service area was spared, our neighbors nearby suffered losses felt near and
far. Being here for each other and facing challenges together with hope is how we take care of each other and it’s how we take care of our groundwater, too. So this Groundwater Awareness Week, our
focus is on all the ways we are here for each other—from the collective efforts to help our friends across the region recover from these fires to the ways we take care of the waters that connect 1.5
million of us in the San Gabriel Valley every day. We’re here, together.

Hello, San Gabriel Valley Friends and Family —I’m Russ, the new Executive Officer at Watermaster and am sending you this...
10/16/2024

Hello, San Gabriel Valley Friends and Family —
I’m Russ, the new Executive Officer at Watermaster and am sending you this note about the water that connects 1.5 million of us in the San Gabriel Valley — our groundwater. Held deep, down underground, groundwater is our common ground and common cause. Watermaster manages this water and the natural, underground basin that holds it. With our partners and you, we are
taking action together to help our groundwater and basin recover from recent droughts and to meet new challenges like getting too much stormwater all at one time. We all play an important role in the story of our groundwater. Thank you for being part of the journey.

We’re sending a big thank you to our water partners for how we’re working together in drought and drought recovery. Team...
05/14/2024

We’re sending a big thank you to our water partners for how we’re working together in drought and drought recovery. Teaming up with our partners – Three Valleys Municipal Water District, Upper San Gabriel Valley Municipal Water District and the San Gabriel Valley Municipal Water District, as well as MWD and LA Flood Control – makes it possible to catch and keep most of the rain that falls in San Gabriel Valley, turning rainfall into our
groundwater. For our water we are taking action together.

We’re celebrating May with gratitude for our groundwater and you! There’s 1.5 million of us in theSan Gabriel Valley who...
05/07/2024

We’re celebrating May with gratitude for our groundwater and you! There’s 1.5 million of us in the
San Gabriel Valley who are connected to one amazing source of water – our groundwater. We all
are an important part of its story. That’s the story of our drought cycle and how we are continuing
to work together to help our groundwater recover from the last drought before the next one
begins. To know more about the story, visit us at: thewatersthatconnectus.com.

This Earth Day we’re sharing the story of rain, runoff and drought recovery. It’s the story of what’s happening deep dow...
04/22/2024

This Earth Day we’re sharing the story of rain, runoff and drought recovery. It’s the story of what’s happening deep down underground below the beauty of spring flowers in bloom. Our goal always is to capture and store stormwater’s rain when it falls, but if too much falls at once, like it did during the recent extreme storms, it can be more than our stormwater systems can capture. That excess rain is stormwater runoff because it “runs off” never entering our groundwater supply to help with drought recovery. We’re not leaving our water up to the weather, this Earth Day and every day, we can all help our groundwater recover from the last drought before the next one begins. Explore more at: WatersThatConnectUs.com/Challenges.

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725 N Azusa Avenue
Azusa, CA
91702

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Wednesday 8am - 5pm
Thursday 8am - 5pm
Friday 8am - 5pm

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