Scott Valley Groundwater Study Plan 

The Regional Water Board (RWB) has requested that the County of Siskiyou, in partnership with the Siskiyou RCD and other stakeholders, produce a plan for investigating the following about the Scott River Watershed:

1. The connection(s) between groundwater and surface water (Scott River);
2. The impacts of groundwater use on surface water flows and temperatures;
3. The impacts of groundwater levels on the health of riparian (streamside) vegetation (trees).

Why is this information important?

To find out if groundwater use may be reducing summer and fall flows in the Scott River, where temperatures have been shown rising to levels harmful to salmon, and if this is the case, how large (or small) an impact pumping may be having on the river as this has never been tested.

Who has developed this study plan?

Given the potential importance of these studies to communities and water users in the Scott Valley, the Scott River Watershed Council invited Dr. Thomas Harter, specialist in the Groundwater Cooperative Extension Program with the University of California at Davis to design the Groundwater Study Plan, and potentially carry out much or all of the research. Local Cooperative Extension faculty (Farm Advisors) have a long record of professional service in the county and possess a thorough understanding of local agriculture and irrigation practices. More information on Dr. Harter and his groundwater hydrology program at UC Davis can be found at http://groundwater.ucdavis.edu.htm.

What do water users stand to gain from the investigations?

Data collected by the California Department of Water Resources (DWR) indicate that, despite the apparent expansion in the use of groundwater for irrigation, the central Scott Valley aquifer has consistently been recharged each spring, while late summer groundwater levels have been lower in recent years than they were historically. The Groundwater Measuring Program begun by the Scott River Watershed Council in 2006 has shown the same results for the valley floor, but has found that the rate of aquifer recharge may vary a great deal in different regions around the valley. The aquifer's usable capacity is limited and some estimates suggest that current pumping levels might be approaching a practical limit. Since groundwater extraction by users "upstream" (up-gradient) may, in some circumstances, reduce groundwater availability for other users, a better understanding of the Scott Valley aquifer could be useful for water users - especially while there may still be some room to plan for future developments. At present the real capacity of the aquifer isn't known, either in total or in specific regions, nor is it known how it behaves under different environmental conditions and local pumping practices, or how and where it most influences the Scott River. That information could allow water users in the valley to develop management strategies which may improve their ability to maintain the river fishery in good condition, and minimize interference between water users while continuing to make good use of this valuable resource.

What benefits to water users could be provided by the proposed studies?

* Information on the potentials for or limits of groundwater development in specific locations around the valley.
* Potential options for accelerating or sustaining local aquifer recharge in areas that have more limited storage capacity.
* Estimates of the time required for recharge under different conditions.
* Irrigation and other water management alternatives coming from the field trial projects, such as:

Testing flood irrigation vs. sprinkler (pivot) irrigation as alternatives for manipulating river flows - under what circumstances (if any) could they contribute to improved river conditions?

Testing unlined irrigation ditches vs. lined/piped irrigation ditches as alternatives for manipulating river flows - is it better to use seepage from unlined ditches for maintaining river levels via groundwater, or would reducing diversion volume by lining the ditches be more effective (ditches may leak 30-50% or more of the water that passes through them).

Accelerating aquifer recharge by filling unlined irrigation ditches with winter stream runoff and letting water seep out - is there enough capacity in the ditches, and enough available space in the aquifer in late winter/early spring for this to work?

Accelerating aquifer recharge through late winter/early spring field irrigation using winter stream runoff - can enough water be applied to fields, and is there enough unsaturated soil below fields in late winter/early spring for this to work?

Temporary reductions in groundwater pumping at strategic times - are there places in the valley where this could allow river levels to be maintained at critical times?

Stream bed restoration - are there sections of the Scott River channel that are down cutting, and, if there are, would bed restoration work as a remedy?

Building several weirs (low dams) across main stem Scott River, with fish ladders - could this be effective in delaying groundwater loss to the river, and/or providing suitable fish habitat during low-flow periods?

* The potential for interference between irrigation wells in areas where groundwater supply can be limiting (long-term water table data, groundwater model(s), pump tests).

Is this a federally mandated responsibility?

The RWB will continue to fulfill its federally-mandated responsibility for protecting water quality under the Clean Water Act by pressing for changes in water management in the Scott Valley that appear necessary to reach targets for sediment and temperature reductions. At this point, all the RWB has to go on are "best guesses" drawn from data that is incomplete and, in some cases, poor in quality. Regulations devised using this information may do as much harm as good - but the Board is required to show the EPA that it is taking meaningful action, as best as is possible. While the RWB has no authority to regulate groundwater use, it has the authority to set the water quality targets for the Scott River, which in turn may make it necessary for water users themselves to adjust groundwater management. It can be argued that, whatever the perceived risk of "bad news" for water users resulting from the proposed study projects, this more detailed information is not likely to produce worse circumstances than regulations which may otherwise be imposed on the basis of guesswork. The studies outlined in Dr. Harter's groundwater study plan should at least help identify what the real problems are and lead to practical solutions for irrigators operating in areas where some irrigation practices may have negative effects on river conditions.

Is this a voluntary study? 

In order for the Scott Valley Groundwater Study Plan to work, it must have community involvement.  This plan is giving landowners the opportunity to get involved in matters that greatly concern them.  The struggle between irrigation water and fish water must be met head on, and taking part in this study is a fine way for landowners to play a role.  The study plan could be a major step in finding the balance between irrigation use and river fisheries in the Scott Valley.

There is a strong possibility that water restrictions will be enforced on agricultural irrigators in the near future.  If and when restrictions come, water users will need to have accurate information that states, in detail, the actions and affects of the aquifer on a private and community level.  To not be involved in this program means that non-participating landowners could be subject to inaccurate information in regards to their ground water and how it interacts with the surface water.  Currently this plan provides us with the best way to identify and solve the real problems irrigators face in the Scott Valley. 

Other commonly asked questions regarding the Groundwater Study Plan answered by the Scott River Watershed Council Water Committee:

1. Will the information be made public?  Only information about the activity of the wells will be presented to the public.  It is important to know that during public meetings and forums participants will be recognized by a well number that is issued at the beginning of the landowner's participation in the study.   This number will be used whenever the well is being talked about in a public setting by the RCD, and Watershed Council.  Although every effort will be made to protect the identity of landowner participants, absolute confidentiality cannot be guaranteed.

2. Who will gather the data?  The information will be gathered by staff at the RCD and compiled by Ryan Hines, an assistant to Dr. Harter. 

3. Will landowner water be shut off if irrigation proves to be overly damaging to the river and or aquifer?  No.  As of now there are no laws within the state of California that can enforce the stoppage of ground water pumping on private and agricultural land. 

4. Can landowners back out of the Groundwater Study at any time?  Yes.  If at any time a landowner feels that they no longer want to participate in the program they can discontinue their involvement by contacting the RCD or Scott River Watershed Council informing them that they no longer wish to participate in the study. 

5. How do I know that this project will not do more harm than good?  The study is not meant to cause any negatively whatsoever.  The goal is to simply understand to relationship of ground water and surface water interaction.

 

6. How is this Groundwater Study Plan connected to the current Scott Valley static groundwater well measuring program?  It is important to know that the current Scott Valley static groundwater well measuring program is not an offshoot or a "step" of the Scott Valley Community Groundwater Study Plan.  The well measuring program measures the static ground water only, and records the aquifer's level and rate of recharge across Scott Valley.  The information gathered from this current program could be taken into consideration by