I like the definition of environmental sustainability as “providing for current needs without degrading the ecosystem that will support future generations”. We know our water use is not sustainable when saltwater is steadily intruding into the groundwater in the Pajaro Valley, forcing the abandonment of agricultural wells along the coast. In mid-County, the Purisima Aquifer is in danger of the same fate as its southern neighbor. And in the San Lorenzo River watershed and streams along the county’s north coast, the populations of steelhead have declined precipitously since 1970. Coho salmon can no longer be found in the San Lorenzo River.
How did we get here? Were there signs along the way that could have given us a clue that we were headed past sustainable water use? And how do we best achieve sustainable use?
Part 1: Soquel Creek Water District
The History of the Soquel Creek Water District, by Sandy Lydon, published by the District in 1989, details the decisions that led to an overdraft of the District’s water supplies. If recovery from unsustainable use of resources is like recovery from addiction, then the current Board of the Soquel Creek Water District have pierced the bubble of denial about the nature of their problem. The bubble lasted for twenty years.
The first District estimate of the sustainable yield of their groundwater was performed by the US Geological Survey (USGS) in 1967. According to that study the sustainable yield was 7700 acre feet per year.
In 1979, the USGS, led by a geologist named Muir, revised the estimate downward, to 4000 af/y. This shocking estimate prompted the District to enact a moratorium on new water hook-ups. The moratorium on construction came at the end of a decade that saw the County population grow by 56%. Needless to say, a moratorium on growth was a controversial step for the District. Simultaneously, the District sought a second opinion on sustainable yield, hiring consultants, Luhdorff and Scalmanini. That consultant came up with an estimated yield that was three times the Muir estimate.
The District lifted the moratorium and opted to retain Luhdorff and Scalmanini as their consultant for the next two decades. When rising salinity levels in District test wells could no longer be ignored, and new board members were elected, the District switched consultants. The District’s current consultant, Hydrometrics, estimates a sustainable yield of 4200 af/y, equivalent to what Muir estimated in 1979.
The current board members of Soquel Creek Water District are trying to deal with a aquifer system that was degraded by the decisions of their predecessors. The District must first allow the aquifers to recover from low water levels before the sustainable yield estimate of 4200af/y can be safely tapped. To allow the aquifers to recover, the District aims to reduce its annual pumping from the current 4000 acre-ft. to 2900 acre-ft, a drop of 1100 acre-ft. The District’s plan has been to achieve the pumping reduction primarily through using desalinated water.
Transfers of San Lorenzo River water during plentiful flows, a concept under development by the County Water Resources Director, John Ricker, has potential to meet a large portion of Soquel Creek’s pumping reduction goal. Ricker describes one of the scenarios under investigation, “If water rights were increased and pumping capacity was upgraded… Soquel Creek District [would receive]an average of 810 af/yr”.
A little co-operation from Santa Cruz in the form of a transfer agreement would give a huge boost to their recovery. The District has formally asked Santa Cruz to apply to the state for a water rights amendment that would permit a transfer. The ball is in Santa Cruz’s court.