Assessing Our Liquid Assets
A Report Card to the Community
King County and the Groundwater Protection Committee had an insert in the Beachcomber Assessing Our Liquid Assets to help Vashon Island residents learn about their water resources.
The Assessing Our Liquid Assets insert and related Sustainability Indicators are offered in Adobe Acrobat format. For help using Acrobat, please visit our Acrobat help page.
The Groundwater Protection Committee has developed a set of indicators to measure the sustainability of our Island water resources. Each indicator has a target which was assessed in 2010 and for changes through time (2001-2010 Status). These indicators use resource monitoring being done by a variety of stakeholders including Island Water Purveyors, local volunteers, and King County staff. These 11 indicators are grouped into broad categories:
1A Nitrate (745 Kb)
Nitrate is an indicator because it can reflect changes caused by human activity and has some documented health effects at elevated levels. Nitrate concentrations are influenced by septic systems, fertilizers, manure, atmospheric deposition, and nitrogen-fixing vegetation.
1B Arsenic (448 Kb)
Arsenic is tracked as an indicator because it has been detected in some Island wells and has potential carcinogenic effects. Sources of arsenic in water can be natural geologic deposits, pesticides, and industrial pollution.
1C Chloride (491 Kb)
Chloride is a water quality indicator because elevated chloride concentrations in groundwater can be caused by over-pumping of wells allowing saltwater from Puget Sound to enter our aquifers. Elevated levels of chloride can also come from urine and be a tracer of animal-generated pollution, including from humans.
2 Surface water (468 Kb)
The "Water Quality Index" integrates key factors into a single number that can be compared over time and across locations. The index uses monthly data of temperature, pH, fecal coliform, dissolved oxygen, suspended solids, and nutrients and calculates a composite number for each stream between 1-100; the higher the score, the better the water quality.
Marine (Quartermaster Harbor)
3A Dissolved Oxygen (298 Kb)
Tracking dissolved oxygen in Quartermaster Harbor is chosen as a sustainability indicator because most marine organisms need oxygen to live and the concentration of oxygen can be depleted due to nutrient input, particularly nitrogen
3B Fecal Coliform (252 Kb)
Fecal coliform bacteria are monitored to assess fecal contamination from warm-blooded animals including humans and livestock.
4 Groundwater (664 Kb)
Water table elevations are measured in numerous locations and in several different aquifers as an indicator of water quantity. The water table levels can be influenced by the amount of precipitation, changes in groundwater recharge rates due to land-use changes and changes in water use patterns.
5 Flow – Summer Low (446 Kb)
The summer seven-day low-flow rate in our streams is a metric to follow because changes in summer flows can indicate changes in our hydrologic systems and maintaining sufficient water in summer is critical for in-stream wildlife, such as salmon.
6 Flow – Flashiness (477 Kb)
Stream flashiness (as measured by the Richards-Baker (R-B) Index) can detect changes in how fast and how much water gets to our streams after a typical rain storm. Stream flashiness is influenced by changes in development patterns and land cover and can influence the habitat quality of a stream.
7 BIBI (478 Kb)
Benthic macroinvertebrates are the critters -- like mayflies, caddisflies, and stoneflies -- which live on or near the bottom of the stream. A robust and diverse community of these organisms is an indicator of ecosystem health. Changes in the stream flow, increased sedimentation and excessive nutrients or contaminants can have a negative effect on this sustainability indicator, the "Benthic Index of Biologic Integrity" or BIBI score.
8 Salmon Watchers (224 Kb)
We recognize there are numerous factors beyond the purview of our community which influence the number of salmon in our streams including oceanic conditions, fishing, and climate change; however it is our goal to retain the hydrologic conditions conducive to salmon viability in our streams. The number of salmon reported per survey year has decreased since 2001 for several creeks. However, the number of volunteers reporting the data and the number of sites surveyed has also decreased over the same period. At this point, there is insufficient data to conclude whether salmon populations are maintaining.
Water Use and Management
9 Total Use – Island Wide Assessment (649 Kb)
Total island-wide water usage is estimated year to year using data from many public water systems, a few private well owners, and agricultural users. Water use is influenced by weather with overall usage higher in the dryer years. Tracking annual water usage helps us better understand how humans influence the local hydrology. Total water use was estimated to be 495 Million gallons per year for 2010
10 Per Capita (186 Kb)
Per capita water consumption is calculated from the total island-wide water use divided by the population. 2010 Per capita water use of 80 gallons per day is based on an average of the two largest group A PWS per capita data (70 and 90).
11 Peaking Factor (185 Kb)
The summer peaking factor is an indicator of how much additional water people use during the summer. It is calculated from the maximum consumption divided by average usage. Summer water use factors range from 1.2-4.4 based on data from selected Group A public water systems. The peaking factor can be influenced by weather conditions as well as water rates.
For questions about the Assessing Our Liquid Assets insert, please contact Greg Rabourn, Manager, King County Groundwater Protection Program. The Assessing Our Liquid Assets insert is a collaboration of Vashon-Maury Island Groundwater Protection Committee and King County Water and Land Resources Division.