Modeling the Middle and Lower Cape Fear River using the Soil and Water Assessment Tool Sam Sarkar Civil Engineer

Transcription

1 Modeling the Middle and Lower Cape Fear River using the Soil and Water Assessment Tool Sam Sarkar Civil Engineer Outline Problem statement and project objectives Watershed model development Model calibration and validation for flow, sediment and nutrients Watershed loading maps Alternative management scenarios 1

2 Problem Statement and Project Objectives The Problems Cyanobacterial blooms above Lock and Dam #1 Ecological and drinking water supply issues Towards a Solution Water Fund The Nature Conservancy Reduce nutrient loading to the Cape Fear River Project Objectives Identify point and non-point sources of nutrient loadings Quantify loading under existing conditions Load reduction scenarios Watershed Model Development The Soil and Water Assessment Tool Outflow of Haw and Deep Rivers to Lock and Dam #1 HUC12 scale 30 m DEM NLCD 2006 SSURGO soils Weather forcing - NLDAS-2 Point sources 2

3 Model Calibration and Validation Hydrology Daily flow at USGS gages Water balance Evapotranspiration Water Quality Monthly regression loads at Cape Fear River Basin Monitoring Coalition Paired loads Calibration period WY 2006 to WY 2013 Validation period WY 2000 to WY 2005 Hydrology Calibration and Validation Water Budget Lautier, 2006 (NC DENR), Hydrologic Framework and Ground Water Conditions in the North Carolina Southern Coastal Plain (adapted from Hardin, Fine, and Spruill, USGS, 2003 and Wilder, 1978) 3

4 Hydrology Calibration and Validation- Evapotranspiration Daily Average Flow (cfs) Hydrology Calibration and Validation Flow Simulated flow generally in good agreement with observed flow Daily NSE values generally greater than 0.4 and 0.9 on the tributaries and mainstem, respectively Total volume error less than 10% Observed Flow Duration (10/1/2006 to 9/30/2013 ) Modeled Flow Duration (10/1/2006 to 9/30/2013 ) 8000 Average Modeled Flow (cfs) Avg Flow (10/1/2006 to 9/30/2013) Line of Equal Value Best-Fit Line y = x R² = Average Observed Flow (cfs) Flow (cfs) Avg Monthly Rainfall (in) Avg Observed Flow (10/1/2006 to 9/30/2013) Avg Modeled Flow (Same Period) Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Month Monthly Rainfall (in) 202 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Percent of Time that Flow is Equaled or Exceeded 4

5 Water Quality Calibration and Validation Model performance poor at the Rockfish Creek location Model performance fair to very good at all other locations Non-Point Sediment and Nutrient Loading 5

6 In-Stream Sediment and Nutrient Loading Alternative Management Scenarios Reforestation The importance of Long Leaf Pine Point Sources How big is their contribution? Fertilization & Setting Realistic Expectations no more N and P!! Combining options Controlled drainage and wetland BMPs (revised) 6

7 Reforestation Non-point TN and TP load reduction by 4% and 43%, respectively. TN and TP load reduction by 1% and 3%, respectively, at Lock and Dam #1 Point Sources Top 4 NPDES dischargers Fort Bragg WWTP Cross Creek WWTP Rockfish Creek WWTP Smithfield Packaging Company Inc. 100% and 30% load reduction scenarios 100% scenario 10% (TN) and 18% (TP) at Lock and Dam #1 30% scenario 3%(TN) and 6% (TP) at Lock and Dam #1 7

8 Fertilization and Setting Realistic Expectations Reduction in commercial fertilizer and manure application 42% reduction in non-point TP load when external TP sources are removed 13 % reduction in response to 30% external TP reduction 4% reduction in nonpoint TN load in response to 30% reduction in TN application Combining Options Longleaf Pine along with 30% reduction in TN and TP application 4% and 46% reduction in non-point TN and TP loads, respectively 4% and 43% reduction in non-point TN and TP loads, respectively 8

9 Controlled Drainage and Wetlands Controlled Drainage Adjust height of drainage outlet during different times of year Control water table depth to maximize competing demands for plant growth and denitrification potential Wetlands Increase hydraulic retention time of wetlands in the Lower Cape Fear River 1% and 28% reduction in non-point TN and TP, respectively Questions? THANK YOU! 9