Linked Watershed-Lake Models for the Lake Whatcom Phosphorus TMDL Paul Pickett and Steve Hood Washington Department of Ecology

Where? 11 Feb Puget Sound Georgia Basin Conference

What? Monomictic lake Over 100 meters at deepest Twenty kilometers long Glacial sills -> Three Basins Largest basin (96% of volume) average depth over 50 meters Other basins about 10 meter average depth Most development around two smallest basins 11 Feb Puget Sound Georgia Basin Conference

4 11 Feb 2009 Problem Lake Whatcom fails to meet oxygen criteria –Trend: anoxic hypolimnion sets up earlier –Criterion: within 0.2 mg/l of natural conditions –Phosphorus loading causing oxygen decline Just over 10% of watershed developed –Developed tributaries have highest nutrient levels

2009 Puget Sound Georgia Basin Conference Response Loading Obligatory Flow Chart HSPF Tributary Load Fixed Parameters Fixed Loads CE QUAL W2 Dissolved Oxygen Results Meets Criteria ? Done Revise Rollback Y N 11 Feb 20095

HSPF input Base Scenario: 1992 National Land Cover Dataset, with photo update to Base Scenario: 1992 National Land Cover Dataset, with photo update to Full Buildout Scenario: development to allowable zoningFull Buildout Scenario: development to allowable zoning Full Rollback Scenario: all watershed Mixed Forest or wetlandsFull Rollback Scenario: all watershed Mixed Forest or wetlands Partial Rollback: Change land cover from developed to forest until standards are metPartial Rollback: Change land cover from developed to forest until standards are met 11 Feb Puget Sound Georgia Basin Conference

Model View of Rollback Developed areaDeveloped area –pink/brown –Approx 3600 ac Changed to Mixed ForestChanged to Mixed Forest –light green 11 Feb Puget Sound Georgia Basin Conference

Developed Acres vs. Tributary Loading 11 Feb Puget Sound Georgia Basin Conference

The Rollback View 86% Rollback 94% Rollback 11 Feb Puget Sound Georgia Basin Conference

CE QUAL W2 2 Dimensional –Laterally averaged segments –Variable depth layers Dynamic –Time-step selected based on transit times Hydrodynamic –Simultaneous equations to balance, water, temperature, chemistry, growth, death 11 Feb Puget Sound Georgia Basin Conference

CE QUAL W2 Lake Whatcom enhancements –3 algal groups –Sediment variable stoichiometry and decay Sediment stoichiometry linked to water column Both 0 th order and 1 st order sediment decay w/ different nutrient release rates –Looping methodology Rerun model using end conditions of one loop for beginning conditions of next loop Allows model to reach equilibrium from loading changes (15 year retention in Basin 1) 11 Feb Puget Sound Georgia Basin Conference

CE QUAL Plan 11 Feb Puget Sound Georgia Basin Conference

CE QUAL Cross Section 11 Feb Puget Sound Georgia Basin Conference

CE QUAL results: spring 11 Feb Puget Sound Georgia Basin Conference

CE QUAL results: fall 11 Feb Puget Sound Georgia Basin Conference

Cumulative Volume 11 Feb Puget Sound Georgia Basin Conference

Bottom Line Developed area needs to generate phosphorus loading like pre-developmentDeveloped area needs to generate phosphorus loading like pre-development –Partial Rollback from Base Scenario 86% reduction86% reduction –Partial Rollback from Full Buildout Scenario 94% reduction94% reduction Stormwater storage and infiltration are keyStormwater storage and infiltration are key Better land use practices reduce nutrients before they are releasedBetter land use practices reduce nutrients before they are released –Fertilizer, erosion, human and pet waste 11 Feb Puget Sound Georgia Basin Conference

Lake Whatcom TMDL Thanks to: WWU – Institute of Watershed StudiesWWU – Institute of Watershed Studies City of BellinghamCity of Bellingham Whatcom CountyWhatcom County Lake Whatcom Water and Sewer DistrictLake Whatcom Water and Sewer District EPAEPA Portland State UniversityPortland State University CDMCDM Tetra TechTetra Tech Backgrounds courtesy of Gordon Tweit and Anne Kreft 11 Feb Puget Sound Georgia Basin Conference