WESTERN GROUNDWATER CONGRESS: Water resources management in the Pajaro Valley Basin

The Pajaro Valley is home to a billion-dollar agricultural industry, it’s rich, fertile soil providing fruits and vegetables for the nation and all grown with groundwater.  Located on the Central Coast, the Pajaro Valley has no connection to the State Water Project or to otherwise bring in imported water.

In 1980, the Department of Water Resources published Bulletin 118, identifying the Pajaro Valley as one of eleven basins in the state considered critically overdrafted.  Community leaders recognized that local management of the groundwater basin was necessary as seawater intrusion was already impacting agricultural water supplies as well as domestic wells; however, there was no single agency with authority to manage the entire basin which encompasses parts of Santa Cruz, Monterey, and San Benito counties as well as the City of Watsonville.  So in 1984, local legislators spearheaded the state legislation necessary to form the a multi-jurisdictional agency to manage groundwater which was subsequently approved by local voters.

Since that time, the Pajaro Valley Water Management Agency has been working toward sustainable management of the Pajaro Valley’s water resources.  At the 2019 Western Groundwater Congress, General Manager Brian Lockwood discussed the projects and programs the Agency is implementing as they work towards achieving groundwater sustainability.

Mr. Lockwood began by acknowledging that the work he will be describing is a team effort with the Board of Directors, the staff, and consultants who have helped to pull information together, implement the programs, and help complete the projects.  He said that one of the most important functions of the agency is to provide excellent customer outreach and service, as well as basin management planning, supplemental water supply deliveries, hydrologic modeling, and conservation, among other things. 


The map shows the location of the basin, which is at the end of the Pajaro River watershed adjacent to Monterey Bay.  The Agency’s statutory boundary is shown in black lines.  Similar to the Fox Canyon Groundwater Agency in Ventura County, the Pajaro Valley has some of the highest valued farmland in the nation, if not the world, growing high value crops such as strawberries, raspberries, blackberries, and vegetables, most of which are organic.

In years past, they used to grow a lot of apples and so groundwater overdraft was not an issue because apples didn’t need as much water as the higher value crops. 

So Pajaro Valley growers have quadrupled their amount of water use but also jumped up the revenue that the growers are making,” he said.  “They’re getting about $1 billion of crop revenue per year. “

He presented a map showing the crops grown (lower left), noting that the large gray area is the city of Watsonville.  Strawberries are shown in red, vegetables are in green, and the blackberries are grown in the hotter parts of the valley towards the back.  The San Andreas fault acts as a boundary to the basin on the east side of the valley.

Almost all of the agricultural water needs are met with groundwater; in 2018, 94% of demand was met with groundwater, the remainder of the demand coming from mostly from recycled water and a small amount from surface water.  The dots on the map are the wells; there are about 2000 wells, roughly 850 of them are large, agricultural production wells. 

The groundwater is pumped from a stratified aquifer system (lower left).  The valley is bounded on one side by the ocean so as water levels are declining and groundwater storage is depleted, they are experiencing seawater intrusion.

All the wells have been metered since the late 80s into the early 90s.  He presented a graph (upper right) showing water use by sector; the precipitation is shown at the top of the chart, showing that greater precipitation lowers groundwater production.  The dark blue part of the bars is the agricultural water usage, purple is the recycled water use, and the light blue is domestic and municipal use.  Total annual water demand is generally between 50,000 and 60,000 acre-feet per year. 

Mr. Lockwood then presented a series of three slides to show the effect of all of the groundwater pumping on the basin.

The first slide (lower, left) shows the groundwater elevation in the fall of 2015.  Everything in red is below sea level, and it extended all the way inland to the San Andreas Fault, which is a no-flow barrier.  There is some recharge that comes from the hills and the Pajaro River.

By the spring of 2018 (upper, center), the basin had recovered from the drought.  A lot of the wells had been off because of the winter precipitation, so groundwater levels were recovering a bit.  But by fall (upper right), water levels had dropped again as they do every fall after the agricultural season. 

That has resulted in sea water intrusion.  The slide to the left shows the extent seawater intrusion from 1951 to 2017 using 100 milligrams per liter contour line.   He pointed out that the lines have really slimmed in recent years as the supplemental water supply facilities have come online.


At the time the agency was formed, ‘sustainability’ wasn’t the term used, but the legislation does talk about stopping groundwater overdraft and seawater intrusion while keeping agriculture productive and viable. 

So our approach, based on our stakeholders and our board of directors, has been to avoid pumping restrictions at all costs and try to develop additional water supply facilities when possible and if we can, implement a water conservation program that is completely voluntary and helps people to save water,” Mr. Lockwood said.

The map shows the extent of the supplemental water supply service zone.  They are building a project to extend the project up to La Selva Beach to the north.  The supplemental water supply zone covers the area most impacted by seawater intrusion. 

The first project, the Harkins Slough Facility, became operational in 2002.  “It pulls water off of Watsonville and Harkins Slough and puts it into recharge basins where it percolates into the ground,” he said.  “We then use a network of recovery wells to capture water that we’ve recharged and some water that we haven’t recharged but is available, and we send that through our system.”

The water recycling facility has been online for about 10 years now.  Mr. Lockwood said it isn’t as much ‘drought-proof’ as it is ‘drought-tolerant’ because during the drought, with all the water conservation in the city of Watsonville, inflow to the reclamation plant really dropped. 

We were asking people not to worry too much about flushing toilets; just don’t water your lawn,” he said.

Pajaro Valley Water Management Agency partnered with the city of Watsonville and added on a tertiary facility in 2009 to provide recycled water to the Agency.  “It’s not the source of our lowest TDS water,” said Mr. Lockwood.  “This reclamation plant produces water with a TDS of about 600 parts, and then we blend it with other water sources to make it less saline for those salt sensitive crops.  A lot of the strawberry crops don’t like chloride concentrations to be over 150 parts per million.”

He noted that there have been independent studies conducted in the area.  The slide on the upper right is from a study by a PhD student at Stanford University working under Rosemary Knight. 

They used geophysics to do a survey from about Marina all the way to Santa Cruz,” he said.  “In this figure, the fresher water is shown in blue and the saltier water is shown in red.  In the area where we’ve been delivering water the longest is clearly more blue than red to the outside area, so that’s a bit of proof of concept that some of these projects ae starting to work.”

Once the recycled water plant came online in 2009, the Agency started delivering water to Monterey County.  The graph shows the water level in a well in the seawater intrusion zone.

As we’ve seen the water levels decline in this well, we’ve seen chloride concentrations go up,” Mr. Lockwood said.  “Once we started delivering water here, we saw the water levels in the well come up above sea level, which is really the long-term goal.  We went through the drought, water levels came down, we come out of the drought, we’re back up; but we’ve never been back to where we were before the project, so that’s also proof of concept that these are going in the right direction.”


While these projects have been successful, Mr. Lockwood acknowledged there is still more work to be done in order to balance the groundwater basin.  So working with the USGS in 2005, they formed a technical advisory committee, built a hydrologic flow model, and then ran the model, which determined that about 12,000 acre-feet of additional supplies per year on average were needed for the basin to be balanced.

So in 2010, the Board established an Ad Hoc Basin Management Plan Committee tasked to ‘investigate all practical projects and programs that contribute to the efficient and economical management of existing and supplemental water supplies’ and ‘serve as an advisory committee to the PV Water Board so that Board decisions are fully informed and affected and guided by the community’s interests.’

The Committee had 21 members, including agricultural interests, large water mutuals, water districts, environmental interests, community groups, landowners and others.  They met for 2 years.

The end result of their work was, let’s solve this problem of 12,100 acre-feet by conserving more water and let’s set an ambitious goal of 5,000 acre-feet a year, which is about 10% of the average production in the valley,” Mr. Lockwood said.  “Then let’s look at our existing facilities and make them better.  We thought at the time that we could optimize them to get another 3000 acre-feet, and then we need to develop new water supplies at 4,100 acre-feet.”

They put a call out to the community members to send in their ideas and they received 44 different projects and programs – everything from towing icebergs and getting water over from Santa Clara Valley’s reservoirs and letting it trickle down the hill into our basin down to other ideas that were a little more realistic. 

We evaluated them all, and then the group wanted to rate them by cost per acre foot, so we looked at whatever is the least expensive per acre-foot, that’s where we’re going to start and we’re going to build from there,” he said.

With the conservation program, 85% of the funding resources go towards agricultural water conservation with the remainder for home and garden conservation.  Since they are a small agency, they decided to work with partner agencies to leverage their expertise to the greatest extent possible.

That means working with the Resource Conservation Districts and the UC Cooperative Extension and providing funding for their technical experts and their PhDs to get on the farm and work with our growers,” he said.

The conservation program for growers extends at least three years.  In the first year, distribution uniformity and the entire irrigation system is evaluated; the second year, irrigation conservation is applied to a portion of the ranch and the results compared to the rest of the ranch.  By year three, hopefully the techniques have proven to be successful in maintaining the yield without the same water use, which the grower would then expand to the rest of the ranch.  The Agency also pays for some of these improvements.

They also tried an incentive program for fallowing land after the growers asked for such program.  The Agency put up $200,000 and paid growers $1000 per acre to fallow the land.  The Agency did require growers to show that they had been growing on the land in prior years. 

All the money was allocated and was used, but the results weren’t like we had hoped for,” Mr. Lockwood said.  “Everyone who was fallow had planned to be fallow five years prior and just got paid to be fallow.  So we tried it once; it’s not off the table, but we’ll have to figure out a more innovative way to make that happen.”

As for new supplies, there is an additional project to add to the recharge project on the slough system, a project at College Lake, and potentially a diversion off the river at Murphy Crossing.

The Proposed College Lake Integrated Resources Management Project is the biggest project on the table.  College Lake is a lake in the Valley that fills up every year, and a reclamation district has the responsibility of pumping the water out of the lake as quickly as possible so a grower can go in and farm it.

”It’s about 2000 or more acre-feet every year that’s getting pumped into the river and flowing out into the ocean, so our stakeholders said, more than anything else, we want you to take this water from College Lake and use it,” he said.  “So what we’re talking about doing is building a water treatment plant and a weir structure, storing water in College Lake, and then send it via pipelines to the purple area on the prior maps, so we could use this surface water to offset groundwater production.”

Mr. Lockwood pointed out that the Pajaro Valley is completely disconnected from the state’s water supply system, so there are no imported water supplies.  “When we were formed in 1984, part of our mission was to build a pipeline to connect to the State Water Project, but then this group formed that called themselves NOPE which stood for No Overpriced Pipeline Ever.  And so that went away, and since then, our motto has been, local folks working on local solutions, and so this is one.  There’s a lot of benefit here because they are already draining the lake and we can use this water.  It’s about a $50 million project.  This is the furthest one out in terms of making progress.”

Watsonville Slough System Managed Aquifer Recharge and Recovery Project is much like the Harkins Slough facility, except that when the King Tides occur in the wintertime, salt water can sometimes flow upstream as far as 5 miles, so if today’s King Tides are tomorrow’s high tides, that is going to create a lot of problems. 

There are years that go by when we can’t operate the facility now because the water is too salty,” he said.  “So the new diversion is going to be located further upstream in an area that the water quality shows doesn’t get affected by seawater intrusion, so it’s a little bit of a retreat scenario in the face of climate change.”

They have also been working on a pilot project to try out a recharge net metering program, which came after the basin management plan.  The program fits with the Agency’s strategy of diversifying their ability to capture and get water back into the basin.

Mr. Lockwood explained how the program works.  “We work with private landowners to identify if their area is suitable for groundwater recharge,” he said, noting that the areas in green on the map are suitable for recharge and those in pink are not as suitable.  “This pilot program has a goal of recharging in total 1000 acre-feet per year which could be expanded potentially in the future.”

If you a build a basin on your land to capture the natural runoff that is flowing through your ranch, and we’re monitoring the water quality to make sure the water that is infiltrating into the ground is at least as good as if not better than the water quality that’s in the subsurface, particularly with respect to nitrates, then we will pay a rebate of 50% of our groundwater augmentation charge,” he continued.  “That augmentation charge and most of our revenue comes from a fee that’s applied to pumping your own well.  The augmentation charge is usually $246 for every acre-foot pumped, and the grower would get 50% or $123 multiplied by how much water was infiltrated into the ground as determined by our Third Party Certifier.  The Third Party Certifier is a combination of the university, Andy Fisher and the grad students, and the RCD.  So if you put 100 acre-feet into the groundwater basin, you could a rebate check from us for about $14,000, which helps to pay for the costs to install that or to do maintenance because you have to clean it out to remove the silt.

Mr. Lockwood closed with a model simulation which shows water levels coming up through time with the implementation of the plan.   

We do have an approved plan with the state which is an alternative to a Groundwater Sustainability Plan, so this is the direction we’re going,” he said.


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