Water Quality Modeling of Lake Chaplain Reservoir for Understanding Long Term Operational Changes
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The City of Everett withdraws drinking water from the south end of Lake Chaplain Reservoir averaging 40 MGD in the winter and 100 MGD in the summer. A paper mill had been withdrawing about 30 MGD from the north end of the reservoir until it was shutdown in March 2012.

The City is concerned that this could result in reservoir water quality changes over the long term and possible short-circuiting of reservoir inflows to the drinking water intake. The City is interested in using a water quality model to investigate any impacts to operations from the withdrawal changes and possible solutions. This study is key study for the City to evaluate if there a long term impact to reservoir water quality and what operational changes might be pursued to mitigate any impacts. A CE-QUAL-W2 model of the Lake Chaplain Reservoir was developed and calibrated for a 3 year window and then run for a 10 year long term simulations to understand the impact of withdrawal changes on water quality. CE-QUAL-W2 is a two-dimensional hydrodynamic and water quality model that includes typical eutrophication parameters (algae, nutrients, temperature, organic matter, dissolved oxygen, pH). Operational scenarios were developed and tested to explore water inflow and withdrawal alternatives to maintain current water quality conditions over the long term.

Publication Summary

  • Geosyntec Authors: Rob Annear
  • All Authors: Anna Thelen, City of Everett, WA
  • Title: Water Quality Modeling of Lake Chaplain Reservoir for Understanding Long Term Operational Changes
  • Event or Publication: AWWA Pacific Northwest Section Annual Conference
  • Practice Areas: Surface Water/Groundwater Supply Studies and Development
  • Date: 2013
  • Location: Spokane, WA
  • Type: Presentation