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Water Quality Model: Flow Input Needs and Low Flow Selection. December 14, 2011 Laura Weintraub. TROM Flow Disaggregation for Input to Water Quality Modeling. TROM Output: Oct – Apr: monthly May – Sep: bi/tri-monthly Three types of data linked to WQ models: Reservoir releases Diversions
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Water Quality Model:Flow Input Needs and Low Flow Selection December 14, 2011 Laura Weintraub
TROM Flow Disaggregation for Input to Water Quality Modeling • TROM Output: • Oct – Apr: monthly • May – Sep: bi/tri-monthly • Three types of data linked to WQ models: • Reservoir releases • Diversions • TMWRF effluent discharge • What spatial / temporal disaggregation of TROM flows is needed?
Application of TROM Flows: Time Scale • Reservoir Releases, TMWRF, diversions: • WARMF hydrologic calculation of tributary flow will include daily variation • Check streamflows with TROM Output Apply monthly / bi-monthly TROM flow directly; use step function to fill daily values
Application of TROM Flows: Spatial Scale • Truckee Meadows Diversions have individual output • TROM output used directly • Lower River Diversions lumped into 2 parts • Vista Gage to Derby Dam • Derby Dam to Pyramid Lake • TROM output will be “split” to correspond with correct river segments in model based on current diversion records and/or water rights
Use of TROM Model Output to Select Low Flow Year • 100 years of predicted flows: 1901 - 2000 • TROM Scenarios: • Future No Action: • Estimated “Buildout” Level of Development (2033) • Truckee River Agreement Operations (TRA) • Future TROA: • Estimated Buildout Level of Development • Truckee River Operating Agreement Operations (TROA)
TROM Flow Ranking Analysis • Tool for assessing flow ranking based on a variety of methods • Two Scenarios: Future No Action, Future TROA • Considered Six Locations • Farad, Sparks, Vista, Above Derby Dam, Below Derby Dam, Inflow to Pyramid Lake • Applied Seven Ranking Methods • Minimum annual (lowest flow during the year) • Annual average • Minimum monthly (lowest average monthly flow) • Minimum Irrigation Season (Apr - Sep) (lowest flow during these months) • Average Irrigation Season Apr - Sep) • Minimum Summer (May-Sep) (lowest flow during these months) • Average Summer (May-Sept)
Climate Data Ranking Analysis • Considered five locations from three sources of data • Truckee, CA 1905-1916; 1936-2008 (NCDC) • Tahoe City, CA 1910-2010 (NCDC) • Independence Lake, CA 1979-2011 (SNOTEL) • Sacramento Valley 1906-2011 (California DWR) • San Joaquin Valley 1901-2011 (California DWR) • Three Ranking Metrics • Water Year Precipitation Sum (Truckee, Tahoe City, and Independence Lake) • Water Year River Runoff Sum (Sacramento and San Joaquin) • Water Year River Runoff Index (Sacramento and San Joaquin) • Tool Assessment Methods • Percent rank and absolute rank • Compare with 10th, 25th, 50th, and 75th percentile of the data
Proposed Approach For Low Flow Year Selection • Identify 5 – 10 candidate years based on TROM flow and climate ranking • Review resulting hydrographs for each year • Consider availability of supporting data • e.g., climate, solar radiation • Coordinate with NDEP to select best choice for representative year • Consider most appropriate TROM scenario and characterization of Truckee Canal capacity limits