Illahee Aquifer Issues. Over the years some Illahee residents have been concerned about the increasingly low baseflows in Illahee Creek during periods when there is no or little precipitation, primarily in the summer time. The baseflows in Illahee Creek are supplied from springs (or seeps) that emanate from the shallow aquifers.
Base Flows Critical for Fish. Adequate baseflows during dry periods is crucial for fish survival and are of special concern for those hoping at restoring Illahee Creek’s fish (salmonids) population to near historic levels.
Aspect Consulting Report. A number of years ago Aspect Consulting did an analysis of Illahee Creek during one of the dry summer months to identify the primary locations of the springs supplying the creek and the flows coming from the seeps. The study noted the importance of infiltration of rainwater into the groundwater systems and aquifers, and noted that a proposal to run stormwater to the Sound could decrease the baseflow in Illahee Creek by 15 to 20%.
Parametrix Report. When the Port of Illahee and the Department of Ecology funded the engineering firm Parametrix to conduct a watershed study of Illahee Creek, they included a requirement for an Aquifer Protection Plan to be prepared for the creek. The plan was sub-contracted out to Keta Waters, an engineering firm specializing in hydrology.
June 2009 Briefing. The Aquifer Protection Plan for Illahee Creek was presented at a briefing on June 30, 2009 at the Norm Dicks Center, during which Dr. Joel Massmann of Keta Waters, noted that the Manette Aquifer, which underlies much of Illahee and Illahee Creek, may be at water balance according to his calculations. This was the first time many had heard this and in talking to those attending, many did not understand the situation or the implications.
Water Balance? As we understood the presentation, the Manette aquifer is recharged solely by the infiltration of rainwater, and that recharge amount is also what is being withdrawn for drinking water and what is being discharged into creeks such as Illahee. In other words this aquifer may be essentially at water balance. It will take more studies to confirm this and they were recently authorized, but it will take a number of years before they will be completed.
Implications of Being at Water Balance. If Dr. Massmann is correct, then it seems to us that we should be paying attention to this situation, and understand possible implications: such as What happens if we have a relatively dry rainy season, or several in a row, and we withdraw more water than is infiltrated? Are we in danger of salt water intrusion into the aquifer?
Bainbridge Island USGS Aquifer Study Issued 3/1/11. Dr. Massmann has been invited back to give another briefing on this subject, and will have some more information which he hopes to get from the USGS study of the Bainbridge Island aquifers. This will be another opportunity for residents to better understand the groundwater and aquifer system that lies under us, and what we can do to make sure it remains a viable water resource into the future.
The Press Release. We thought it might be helpful to preface the following press release with our thoughts and concerns in hopes that residents would want to learn more at the briefing:
GROUNDWATER, AQUIFERS & INFILTRATION REQUIREMENTS
A Briefing of the Manette Peninsula Aquifer and the Illahee Watershed Aquifer Protection Plan by Dr. Joel Massmann
A briefing discussing the underlying aquifers in Illahee and the surrounding area will be held at the Norm Dicks Government Center on the evening of March 29, 2011 from 6:30-8 pm.
Dr. Joel Massmann will discuss the underlying aquifers and groundwater recharge on the Manette Peninsula and within the Illahee Creek watershed. The presentation will address questions regarding how much fresh water is in these aquifers, where does this fresh water come from, and where does it go. These questions will be described in the context of relationships between groundwater for municipal supply and groundwater to support stream flow and wetlands.
In June 2009, Dr. Massmann noted that the Manette Aquifer may essentially be at water balance and the water rights for the aquifer may have been over-allocated. (Also in June 2009 the Kitsap County Commissioners adopted a “Water as a Resource Policy” for Kitsap County.) Since that time the Kitsap PUD and local water purveyors have funded USGS to conduct a detailed study of the Kitsap Peninsula that will take several years to complete. In the meantime the implications of local aquifers possibly at water balance needs to be addressed. Dr. Massmann has been invited back to discuss the aquifer issues again and any possible extrapolations for Illahee from the USGS Groundwater Study of Bainbridge Island that was issued on March 1, 2011. He will also provide specific recommendations for protecting aquifers, which are the sole source of our drinking water on the Manette Peninsula.
Dr. Massmann has over twenty-five years of experience as a groundwater consultant. He is the founder of Keta Waters and was previously a faculty member in the Department of Civil and Environmental Engineering at the University of Washington.
Dr. Massmann’s study of the local aquifers was funded in part over the last few years by grants from the National Fish and Wildlife Foundation and the Washington State Department of Ecology; and by the Port of Illahee, the Illahee Forest Preserve, and the Illahee Community.
Comments? If you have any thoughts on this subject, or even disagreements with our comments, we would like to hear them and will include them in a future update, or you can comment on the blog http://illaheecommunity.blogspot.com/ or Facebook.