Part 2 Our Local Water Challenges

San Lorenzo River, 47% of SC water supply

Loch Lomond, 17%                                                 N. Coast streams 32%

Water Challenges Facing Santa Cruz

The big challenge facing Santa Cruz is drought. In 1976-77 the City suffered the worst drought since keeping records 89 years ago. If a similar drought were to occur now, the Water Department estimates that the second year of drought would require peak season curtailments of 39%. (See the table below from the Integrated Water Plan) At 39% curtailment, water rationing would be imposed on businesses and residences, and watering lawns would be illegal (except for golf courses, which would get 20% of their normal year allocation).

Santa Cruz is vulnerable to drought because it gets so little of its water from underground aquifers, just 4%. Water levels in an aquifer don’t fluctuate much in response to short-term droughts. Santa Cruz gets 47% of its water from the San Lorenzo River, 32% from creeks on the North Coast, and 17% from Loch Lomond Reservoir. The Water Department reports that “three of the four major sources are presently being utilized at maximum capacity for a significant portion of the year”.1 The only source not fully tapped is the City’s reservoir. The report continues, “What this means operationally is that any future increase in seasonal or annual demand for water will be felt through greater and greater withdrawals from Loch Lomond reservoir”.

As demand for water grows, the amount of reservoir water kept in reserve drops. That reduces drought security. If growth in water demand continues without the City developing a new supply, the water drawn from Loch Lomond will increase up to the water rights limit of 1 billion gallons per year. As Table 5-2 from the Urban Water Management Plan shows, that leaves only 200 million gallons available for the second year of a worst-case drought. At that point, peak season curtailments would be 46%.

That’s the bad news. The good news is that worst-case droughts are “a statistically rare event”, according to the Water Department. The Department estimates that all other drought events besides the rare “worst-case” drought would require peak season curtailments of less than 20%. City residents have demonstrated their willingness to cope with that level of curtailment.

In this report we explore the following options for Santa Cruz to maintain drought security:
•    Develop a new water supply  
•    Conserve enough water to maximize reservoir levels at the end of the dry season
•    Limit growth in water demand by requiring growth to be water-neutral

Frequency of Peak Season Curtailment

Source: Integrated Water Plan (2003)

Source: Urban Water Managment Plan, (2005)

What about the fish?
There’s a further challenge to having a sustainable water supply. Our current rate of water use is unsustainable because the quantity of water we divert from the San Lorenzo River and North Coast streams has reduced populations of native fish. The National Marine Fisheries Service states, “The most significant limiting factor affecting listed salmonid populations on California’s central coast has resulted from excessive surface and ground water diversions.”2 There are currently no coho salmon reproducing in the San Lorenzo River watershed. That means this species has been “extirpated”, that is, the species is locally extinct.

In 1996 the coho was federally listed as a threatened species. Because coho populations subsequently dropped, the coho was listed in 2005 as an endangered species. The National Marine Fisheries Service (NMFS) is charged with enforcing the Endangered Species Act. According to NMFS regional director, Jon Ambrose, the NMFS began an enforcement action against the City in 2002 regarding its water diversion from Laguna Creek on the North Coast. That legal action is in abeyance while the City makes progress on a Habitat Conservation Plan. The plan would require the City to reduce its diversion of water from the San Lorenzo River and North Coast streams in order to restore habitat for native fish. The NMFS has also recently released a recovery plan for Central Coast coho salmon that identifies the San Lorenzo watershed as a priority recovery area.

The  Habitat Conservation Plan will include an assessment of how much water flow is needed for fish habitat. The City diverts water from the North Coast streams year-round. The water rights to the North Coast sources date from pre-1914, and have no limits on the amount of water that can legally be diverted. A panel of independent scientists commissioned to comment on the City’s Habitat Conservation Plan notes that “the City diverts a substantial proportion of the flow from the north coast streams. The annual average flows are decreased substantially: 35% for Laguna Creek, 18% for Majors Creek, and 36% for East Branch of Liddell Creek. The proportion of flow diverted in dry times is commonly over 80%.3

The City diverts water year round from the San Lorenzo River, including late summer periods when water flows are low. The City has water rights that allow it to divert 12.2 cubic feet per second. The impact of this water diversion is greatest in late summer. September is the period with lowest average water flow in the river, 15 cubic feet per second  at a point just upstream from where the City draws its water. At a stream flow gauge just downstream from the diversion, the flow averages 4 cfs in September, indicating that the City is diverting 73% of the river’s flow.4 In critically dry years, the City has diverted 97% of the river flow.

Any of the possible water solutions we explore in this report: new water supply, conservation, and limits to growth, will include prioritizing the restoration of fish habitat.

1 Adequacy of Municipal Water Supplies to Support Future Development (2004)   p 10
3 Independent Science Advisory Committee, Science Advisory Report for City of Santa Cruz Habitat Conservation Plan, (2004), p.31  Download a pdf copy below
4 Entrix Environmental Consultants City of Santa Cruz Section 10 Program, Appendix A,
 

Water Flow Needs of Native Fish

Winter
The section of the San Lorenzo River between the Henry Cowell Big Trees and Paradise Park is known as the Gorge. Some sections are filled with boulders which are potential barriers to fish that are returning to spawn. In these boulder areas the fish need a minimum of 50-70 cubic feet per second of water flow in order to navigate passage.¹ Upstream of the Gorge is the City’s Felton Diversion. The City inflates a dam during drought years to allow water pumping to Loch Lomond, when the lake is not expected to fill through normal runoff into Newell Creek. State water rights mandate a minimum bypass flow of 25 cubic feet per second at the dam. This is half or less of what the fish need for passage up the Gorge. Reports from the 1977 drought year describe hundreds of returning salmon stranded in the Gorge.²

Spring
“Smolts” are young fish that have undergone the physical change that allows them to survive in salt water. Coho and steelhead salmon molts migrate to the ocean in March through May. They need enough water flow in the river to allow passage downriver to the ocean. During drought years the river has dried up below the City’s main water diversion just above Highway 1. There are no minimum bypass flow requirements at the City’s main water diversion, since the water rights there pre-date public concern for fish habitat.
During low flow periods in the river, the ocean waves create a sandbar at the mouth of the river. This is a normal occurrence in the summers. If the sandbar closes prematurely, smolts cannot outmigrate.

Summer
Summer flows in the tributaries and mainstem of the San Lorenzo River are important for the growth of juvenile salmonids that have not reached the smolt stage. Salmonids can take up to two years to become smolts. They need sufficient water flow for adequate water depth, cool temperature, and a rapid flow of passing insects.  Summer flow (base flow) in Bean Creek and Zayante Creek is affected by groundwater pumping of the Santa Margarita Aquifer by Scotts Valley Water District and San Lorenzo Water District.³ A significant amount of water is diverted from Fall Creek, Boulder Creek and Clear Creek by the San Lorenzo Valley Water District and Lompico Creek by the Lompico Water District.

Improving Water Flow
We need to change the perception that water conservation is important only in dry years. Water agencies have contributed to that perception by calling for limits on landscape watering only in dry years. Later in this report we also discuss proposals to recharge the Santa Margarita Aquifer and watershed restoration to improve base water flow.

1 Swanson Hydrology & D.W. Alley, San Lorenzo River Salmonid Enhancement Plan, (2004)   p. ES-10
2 Don Alley, Fisheries Biologist, Transition Santa Cruz video, Save Some Water for the Fish
3 Swanson & Alley (2004) p ES-11

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