One of Santa Cruz County’s largest water sources is ‘critically overdrafted’; fixes are on the way

More than 50,000 residents of Santa Cruz County are reliant on a single water source: the dwindling Mid-County Groundwater Basin, which the state deemed “critically overdrafted” nearly a decade ago. Now local agencies are embarking on efforts to boost the ability of the basin to capture more rain during the wet months along with an ambitious plan to replenish the basin’s drinking water supply with recycled wastewater.

A number of agencies — including Soquel Creek Water District, the City of Santa Cruz Water Department, the Central Water District — and several thousand private well owners share the underground basin, a reserve made up of a group of linked aquifers, in an area that encompasses the Eastside of Santa Cruz, Live Oak, Soquel, Aptos and Capitola. That’s a lot of sources for one basin to supply.

That, coupled with California’s extended periods of drought, led the state to designate the basin as “critically overdrafted” in 2014. That means more water is being pumped out of the basin than it can naturally replenish via rainfall. Out of 500 total basins in California, Mid-County is one of 21 the state has deemed critically overdrafted, and the state has mandated that local bodies form “groundwater sustainability agencies” to find a solution.

Shortage of available water isn’t the only problem. Pumping too much groundwater from a basin can lower water levels enough to draw seawater inland, contaminating groundwater with salt. This phenomenon is called seawater intrusion, and it has been observed at several locations of the Mid-County Groundwater Basin as far back as the 1980s.

The local groundwater sustainability agency — made up of the three districts that share the basin along with the County of Santa Cruz — was the first to have its basin plan approved by the state. Now, two projects are well underway: Pure Water Soquel and the City of Santa Cruz’s Aquifer Storage and Recovery (ASR) project seek to address the seawater intrusion problem in the Mid-County Groundwater Basin while also maintaining a stable, reliable water supply for the county’s still-growing population.

These projects aim to provide a larger supply of water for county customers, utilize water that would otherwise typically be released into the ocean, and ensure that local water agencies will not rely as much on surface water sources, like the San Lorenzo River and Loch Lomond Reservoir, to supply residents with water. That’s especially vital in an area hit hard by drought, and one dealing with increasingly uncertain weather.

Melanie Schumacher, Soquel Creek Water District special projects communications manager, said that Pure Water Soquel is the result of a year-and-a-half-long process to figure out a usable water source after the Santa Cruz City Council shelved a joint desalination project between the City of Santa Cruz and Soquel Creek Water District in 2013 over fears of high costs and environmental impacts.

Using recycled wastewater proved to be a favorable plan B after the desalination project was nixed, in part because it involves using water that would normally be discarded to act as a new source of municipal water. Now, the $145 million project is just months away from being fully operational, with construction expected to complete by fall 2024.

Pure Water Soquel will take wastewater that has already had pollutants removed and which is typically dumped into the ocean, and instead pump it through 8 miles of pipeline into a new treatment facility, where it will undergo a purification process before it is added to the basin. The hope is that the extra freshwater will provide a sustainable, drought-proof supply of water to the overdrafted basin and create a barrier against seawater intrusion by raising dwindling water levels, preventing seawater from seeping into the supply.

As much as 8 million gallons of treated wastewater is sent out to the Monterey Bay sanctuary every day, said Schumacher: “We’re trying to recapture some of that and put it to beneficial reuse. This is a source of water that isn’t dependent on rainfall.”

The deluge of storms that hit the Central Coast this past winter provide another reason that Pure Water Soquel can help to “climate-proof” the region’s water supply. Not only can destructive storms damage vital infrastructure used to get water to community members, they can also greatly contaminate water sources. Streams and rivers, such as the San Lorenzo River that supplies the city of Santa Cruz, saw extremely turbid, muddy waters during the storms, rendering that water too dirty to be effectively treated.

“When that happens, even though people might think there’s all this water that we can capture and use, those extreme water-quality conditions don’t allow for that water to actually be used,” said Schumacher. “That’s always a threat.”

She explained that, during last winter’s storms, Soquel Creek Water District used an intertie — a connection allowing water to pass between two systems — with the city’s water department and fed the city supply some of its own water. Pure Water Soquel is expected to make it easier to share water, since the water supply will be more stable.

“We’re investing in these kinds of solutions that provide diversification, more reliability, and more resiliency opportunities to come together,” she said. “I think that’s where we need to go, especially in these extreme weather conditions that we’re going to be seeing.”

Meanwhile, the City of Santa Cruz is pursuing its own endeavor to bolster the Mid-County Groundwater Basin supply — the City of Santa Cruz’s Aquifer Storage and Recovery project.

The project would allow more water from strong flows during winter rains to be stored in the basin, bolstering supply and preventing seawater intrusion like Pure Water Soquel. However, rather than using recycled water, the city’s ASR project would pull from existing sources like the San Lorenzo River and Loch Lomond Reservoir and inject it into the basin via freshwater wells. The goal of this project, which is still in its pre-construction phase, is to augment the basin’s water supply so the extra water can be used during drought.

“The idea is that we don’t utilize it every year, but only when our other supplies and flowing streams are running low,” said Heidi Luckenbach, Santa Cruz Water Department deputy director and engineering manager. “Where Pure Water Soquel is just involved with putting water into the basin, we’re putting it in and taking it out when we need it.”

She said that the basin has four groundwater production wells, and the city is working to increase capacity for two of them so they are capable of adequately restoring the basin. That work should be completed by mid-2025, and the city is investigating the feasibility of doubling that to eight wells that could be used for water injection in the future.

Luckenbach said it’s important for the city to inject as much water as possible into the basin, as both the city and the region as a whole have cut back substantially on water use. Local agencies say they can’t ask their customers to cut more than they already have because conservation efforts are already maxed out.

“They’ve already cut everything, they’ve changed up their yards, they’ve improved their appliances to more water efficient versions,” said Luckenbach, who will take over as city water director in February, replacing the retiring Rosemary Menard.

The project holds benefits for excessively rainy periods as well, since it means the basin will be able to capture more stormwater, which often runs off into the ocean because the ground is too saturated to hold any more.

Wild oscillation between extended periods of dry weather and exceptionally wet weather can sow significant uncertainty regarding how much water the basin can retain in a given year. However, with Pure Water Soquel and the city’s ASR project moving forward, officials say they are looking forward to a not-too-distant future when local water departments can bank on an adequate water supply as they wrestle with a changing climate.

“The water system was designed around a certain weather pattern,” said Luckenbach. “It rained from November to May and it was dry from May to October, the reservoir filled, and repeated. It’s not like that anymore.”

Have something to say? Lookout welcomes letters to the editor, within our policies, from readers. Guidelines here.