Regional Water-Swap

Retired Water Manager Calls for Regional Swap

In an editorial in the Santa Cruz Sentinel on April 25, 2010, retired Santa Cruz Water Production Superintendent, James Bentley, wrote, “The City Council has been swayed into accepting a costly and environmentally unfriendly water solution when another viable and sustainable option exists which could minimize or eliminate the need for desalination.” The option Bentley refers to is the water swap with Soquel Creek District — sending wet season water to Soquel in exchange for well water during drought.
Bentley participated in discussions of water supply options in the late 90’s that included this option detailed in the Alternative Water Supply Study (2000). That option was dismissed because the City was concerned that it would lose water diversion rights if it re-opened rights negotiations with the state. That concern is no longer an issue because the City has opened negotiations with National Marine Fisheries Service regarding fish habitat. Bentley calls for putting the water swap option back on the table. The following article includes a description of that option. Bentley’s voice has gotten more press. See the Good Times article, “Water to Share”

Making Use of Winter Flows

John Ricker, County Water Resources Division Director, is exploring two options that would make use of winter runoff to recharge aquifers and improve fish habitat in our streams. The first option is to divert water using existing City of Santa Cruz diversion and treatment facilities during high-flow periods in the San Lorenzo River to restore aquifer levels in Scotts Valley. That water would be used to reduce winter groundwater pumping in Scotts Valley and/or be infiltrated into abandoned quarries to recharge the Santa Margarita Aquifer, where the water is 200 feet below its historic level due to pumping by Scotts Valley. This recharge and in-lieu recharge would increase both groundwater storage and dry season base flow in the San Lorenzo River, improving fish habitat. Another approach in the same area would restore stormwater infiltration in developed, impervious areas of Scotts Valley to increase groundwater storage and reduce storm runoff.

The second option Ricker is exploring is for City of Santa Cruz to send treated surface water during high-flow periods to Soquel Creek Water District. During those periods the District could reduce its pumping of groundwater, thereby allowing the aquifer to recover. This option was considered in a study commissioned by the Santa Cruz Water Department published in 2000.1 That study included the possibility that in return for getting water from Santa Cruz during wet periods, Soquel Creek District would deliver well water to Santa Cruz during droughts. According to the study, “Limited use of the wells by the Soquel Creek Water District during winter periods – when supply could be augmented by the City – should reduce the stress on the aquifer and enhance natural recharge.”

Download John Ricker’s Conjunctive Use report.

Both options would require revision of the City’s water rights to divert water from the San Lorenzo River and possibly the North Coast Streams. Some of those rights date back to pre-1914, when the State didn’t require bypass flows to preserve fish habitat. Consequently, the City has a right to take unlimited water from the North Coast Streams. Its water rights to the San Lorenzo River at the Ocean St. Extension diversion have no minimum bypass flow requirements. Water rights for the Felton Diversion for diversion of high winter flows include minimum bypass requirements, but these may not be adequate, given the increased concern and greater understanding of fish flow requirements. In 2000, the Water Department did not pursue the option of a regional water swap with Soquel Creek District because of a concern that re-opening water rights would allow the State to require significant reductions in summer water diversions. According to Bill Kocher, Santa Cruz Water Department Director, this concern is no longer an issue, since the City has since entered into a process of developing a Habitat Conservation Plan that will modify its water rights to surface streams. However, it remains to be seen to what extent Santa Cruz could get water back during a drought period from either Scotts Valley or Soquel, given that those basins should show recovery before water could be exported.

In order to become viable, these options will need to be endorsed by the government agencies charged with protecting fish habitat. Diverting surface water during periods of high stream flow can be compatible with habitat for fish. The National Marine Fisheries Service Guidelines for Maintaining Instream Flows to Protect Fisheries Resources in Mid-California Coastal Streams states that the period between December 15 and March 31 “is the time of highest winter flow and the time when water withdrawals would be least likely to adversely affect fisheries resources.”2

Salmonids return from the ocean to spawn during the rainy season. In the San Lorenzo River, they need a level of water flow sufficient to allow them to navigate to the upper reaches of the river and tributaries in which they spawn. According to fisheries biologist, Don Alley, low water flow in the gorge section of the river, between Felton and Paradise Park, has been an obstacle to fish migration during dry winters.3 But the City’s main water diversion is downstream from the gorge, near Ocean St. extension. High winter stream flow is not necessary for fish to navigate from the river mouth to the City’s main water diversion. In normal and wet winters, water diversion at Ocean St. extension is not likely to affect salmonid migration. The Water Department has classified 69% of the last 87 years as “normal” or “wet”.4

The cost of the water transfer to Soquel Creek District would vary with the amount of water to be transferred. Two options below describe the possibilities:
1. Low turbidity periods: When the water is not muddy, the City currently uses water from the river and N. Coast streams. In this option, the City would send water to Soquel directly from the treatment plant. There is already adequate capacity at the City’s Graham Hill treatment facility to process water sent to Soquel. There is an existing interconnect pipeline between Soquel District and Santa Cruz, although for a higher volume of water a larger interconnect would be needed. There would also be a need for a new storage facility in Soquel.
2. High turbidity periods: This option potentially provides more water to Soquel for more days of the year and also is more costly. It is unclear whether this option would provide enough additional yield to be justified. In addition to the above pipeline and storage tanks, this would require a pre-treatment facility either on the North Coast or at the Graham Hill Treatment Plant to remove the sediment. The City is already considering upgrades to the Graham Hill Treatment plant to allow more use of high turbidity flows. It would also require expediting the City plan to replace the decrepit pipeline from North Coast sources. Pre-treatment can be mechanical, or it can be accomplished through sand-filter ponds that operate on gravity. This option would have the side benefit of providing the City water during periods of turbidity and saving its Loch Lomond water rights allocation for summer use.
1 Carollo Engineers, Alternative Water Supply Study, 2000, p 1-21
2 ibid p 5
3 conversation with Don Alley
4 Water Shortage Contingency Plan (2009) p 2-6

Other New Water Supply Ideas?

Other water supply ideas that have been investigated:

  • Use of Scotts Valley tertiary treated wastewater on the Pasatiempo Golf Course in return for Santa Cruz water during winter months. Santa Cruz and Scotts Valley District have indicated an intent to pursue this option
  • Wells on UCSC campus. In 1990 a well at the Farm and Arboretum was drilled and tested to determine effects on area springs and streams. The intention of the well was to serve the Farm, Arboretum, and landscapes, which use 150,000 gallons per year, or a third of the current total campus water use. “This test, along with results of 5-year monitoring, indicate operation of the well should not adversely affect streams and springs,” according to the Expanded Initial Study, Farm and Arboretum Irrigation Well, UCSC (1990) available at the Public Library. An article in the SC Sentinel by geologist, Gerald Weber, details this strategy. A different idea for harvesting water on campus comes from Robert Curry, UCSC emeritus professor of geology. “My proposal is for a series of shallow large-diameter wells in the Marshall Field area only.”

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