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Monitoring Spatial Mismatch and Model Mismatch for TMDL and WIP Implementation

This study investigates the spatial and model mismatches in assigning TMDL loads and WIP target loads to monitoring stations. It explores the different flow normalization techniques, confidence intervals, and implementation challenges. The suggested next steps include gathering data from various methods and working towards indicators for the mid-point evaluation in 2017.

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Monitoring Spatial Mismatch and Model Mismatch for TMDL and WIP Implementation

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  1. Goal Lines for Monitoring Gary Shenk TMAW/NTWG 8/15/2012

  2. Cannot Assign TMDL loads to Monitoring Stations • Spatial Mismatch • TMDL is defined on the 92 tidal monitoring segments • Chain Bridge is almost perfect match to POTTF_MD • Conowingo is about 95% of CB1TF • Fredericksburg is about 80% of RPPTF • Others are much worse • Model Mismatch - P5.3.2 vs Estimator or WRTDS • Confidence intervals • Different flow normalization techniques • Implementation vs water quality

  3. Cannot assign WIP Target Loads to Monitoring Station • Spatial Mismatch • Target Loads are defined by state and basin • Patuxent - Maryland • Susquehanna - New York • Model Mismatch • Same reasoning as for TMDL loads

  4. What is the TMDL? (my perspective) 4.5 mg/l Wastewater Loads All other sources 8 mg/l 20 percent slope Agreement to do 55% to 90% of all possible actions, depending on PS/NPS split and position in the watershed

  5. What are the WIPs? (my perspective) Plans to restore water quality that are consistent with the TMDL Illustrative only

  6. What can we say? • We may compare flow normalized load trends to reductions estimated from implementation of WIPs. • Caveats: • WIPs are defined on different scale; some BMP spatial distribution is assumed • WIPs are implementation goals. Lag times are not factored in.

  7. Confidence intervals Different flow normalization methods Different models

  8. Consistent with TMDL decision of “Percent of possible reductions”

  9. Consistent with necessary WQ improvements Estuarine model calibrated to 1990s Critical period 1993-1995

  10. Consistent with WIPs and Milestones Starting now, What are we going to do? Benefit for any method: Chance to examine WSM predictions to determine where and when it works best

  11. Suggested Next Steps • Gather WSM, WRTDS, and ESTIMATOR output at all available locations • IMO, method must be • Flow-normalized • Expressed as a percent reduction • Explained clearly • Need to determine • Appropriate baseline • Display methods • Work toward indicators and possible role in 2017 mid-point evaluation

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