Model Application for WQS Review Process December 14

Model Application for WQS Review Process December 14, 2011 Laura Weintraub

Intended Use of Models for WQS Review • Provide linkage between nutrient concentrations in the Truckee River and resulting dissolved oxygen levels • Account for other factors (flow, temperature, light, organic matter, aeration) • Understand balance of nutrient concentrations which result in DO WQS attainment under a range of flow conditions Sunlight Temperature Flow Dissolved Oxygen Aeration Nutrients (N&P) Organic Matter Algae 2

Water Quality Modeling to Support WQS Review Objective: Identify appropriate (site-specific) nutrient WQS that when met, would adequately meet DO criteria given a representative low flow condition 1. Identify low flow condition 2. Test range of instream concentrations of TN, TP, Ortho-P 3. Evaluate the extent to which the DO water quality standard will still be met 3

% of time DO WQS is violated Conceptual Plot of Model Results Relationship between Nutrient Concentrations and DO WQS Attainment ? (Based on representative low flow condition) Possible Nutrient WQS

Model Linkage – WQS Evaluation Flow Management Model Baseline Run Climate Soil Types WWTPs Nutrient Loads Land Use Watershed Model Management Practices Water Quality Model Water Quantity WARMF Water Quality TRHSPF 5

Model Linkage – WQS Evaluation Iterative Scenarios Flow Management Model Iterations over a range of instream nutrient concentrations will not require additional WARMF runs WWTPs Nutrient Conc. Water Quality Model Water Quantity Water Quality TRHSPF 6

Water Quality Model Linkage 7

Model Assumptions • Flow management model will provide model inputs reflective of historical hydrology under selected river operations: – Reservoir releases – Diversions – TMWRF discharge flows • Climate – consistent with selected representative year • Land use / land cover – updated layer circa 2006 • Evaluate results for Water Year (not calendar year) 8