River Water Transfers

What is it? 

Surface water transfers would include taking excess winter river water that is treated at the  City of Santa Cruz Graham Hill Treatment Plant and delivering it to the Soquel Creek Water District pipeline system. There are currently two options being discussed:

  1. Short Term Pilot Project: Purchasing a small amount of excess water from the City of Santa Cruz (no water rights issues)
  2. Long Term Project: Potentially transferring a larger volume of exess treated winter water from the City of Santa Cruz (requires water rights to be obtained and/or changed)

The District has been looking into this for sometime and has actively participated in studies with the County of Santa Cruz, City of Santa Cruz, and Scotts Valley Water District through an IRWM funded study.  Limitations with this type of project include the reliable amount of water that could be available, since it would only be during the wintertime, and the difficulties with obtaining water rights issues; however, the District continues to be interested in evaluating surface water options to augment other supplies and address part of the water shortage problem.

What are the current activities? 

  • Pilot Project
    • The City of Santa Cruz Water Department offered to sell excess winter river water (Pre-1914 water rights) to the District, and the agreement was finalized in September 2015 and amended in July 2016. To read the Cooperative Water Transfer and Purchase Agreement, click HERE.  
    • Initial Study-Negative Declaration (January 2016).
    • Evaluating water quality impacts with purchasing surface water from the City of Santa Cruz - Tech Memo by Black and Veatch (June 2016)
    • Flushing our District pipelines
    • Amending our DDW Permit

What are some of the things we're considering with surface water transfers and will be evaluating with our pilot project?

The chemical characteristics of groundwater and water from surface water sources (reservoirs and rivers) are different.  Surface water supplies will tend to be softer with lower levels of naturally occurring minerals that, without treatment, will tend to be more corrosive than groundwater supplies.  Surface water will also tend to have higher levels of total organic carbon than groundwater.  While the levels of organic carbon in surface water sources varies considerably, disinfecting water containing organic carbon as part of the water treatment process results in the formation of disinfection byproducts such as trihalomethanes and haloacetic acids. Unless the organic carbon is removed before the disinfection step in the treatment process, disinfection byproducts can continue to form as the water travels through the distribution system.        

Switching sources or blending sources can be a tricky business that requires good understanding of the potential issues, careful and informed management of system operation and good monitoring and feedback loops to adapt operations if and as needed to protect public health and to minimize any aesthetic issues resulting from changing water quality in either water system or customer property plumbing.

Recent issues with source water changes in Flint, Michigan and Fresno, California, for example, are reason to exercise prudence in planning for implementation of water transfers, and two issues have been identified as the focus of efforts to plan for and manage during the implementation of the pilot water transfer pilot project described earlier:

The potential for the City’s softer surface water to cause corrosion of water system or property side plumbing in the District’s system which could result in aesthetic issues such as red or discolored water, or of increased levels of corrosion byproducts such as lead and copper in first flush water; and the potential for continuing formation of disinfection byproducts once water from the City’s system enters the District system, which may be exacerbated by the low turn-over of stored water related to low demand in parts of the District’s distribution system. 

A significant benefit of the planned pilot project is the opportunity to further understand these issues and learn about what approaches are necessary to implement a successful in lieu water transfer program.