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303 (d) & Total Maximum Daily Loads

Lower Catawba River Basin Nutrient TMDL Development in South Carolina

Background

Phosphorus and nitrogen are essentials nutrients for aquatic life and are present in the natural environment. In surface waters, phosphorus and nitrogen are causal variables (nutrients) that control algal growth, which is typically measured by chlorophyll-a. Without adequate levels of phosphorus and nitrogen, a balanced, indigenous aquatic community may not exist in surface waters. However, excess nutrient levels can lead to water quality problems such as algal blooms, hypoxia (low dissolved oxygen), and elevated pH.

Within the Catawba River Basin of South Carolina, Cedar Creek Reservoir, Fishing Creek Reservoir, Great Falls Reservoir, and Lake Wateree reservoirs are considered to be impaired due to excessive nutrients and microscopic algal growth. Basin Map Over 30 ambient monitoring locations within the reservoir system are currently included on the State’s 2012 303 (d) List of Impaired Waters (the most recent biennial list submitted to and approved by The USEPA). Many of these monitoring locations have been included on the 303(d) list for total phosphorus, total nitrogen or Chlorophyll-a since South Carolina adopted numeric nutrient criteria, or water quality standards, for these pollutants in 2004. Elevated pH has also been observed at monitoring locations within the system. Long-term monitoring data have demonstrated these conditions existed prior to 2004 although more recent data are demonstrating some improvement as nutrient reductions have been implemented by utilities in the Basin upstream of the impaired reservoirs.

In accordance with the Clean Water Act and 40 CFR Part 130, Total Maximum Daily Loads (TMDLs) are required to address impaired locations included on a State’s 303(d) list. South Carolina is developing TMDLs to address these impairments in the Lower Catawba River Basin. Once these TMDLs are implemented through permits and voluntary measures, the reservoir system should continue to respond and, over time, achieve the water quality standards as outlined in Regulation 61-68, SC’s Water Classifications & Standards.

Nutrient Model and TMDL Development

TMDLs are currently being developed to address excessive nutrients in the Catawba River Basin of South Carolina. South Carolina is using an existing model application known as Watershed Risk Management Framework (WARMF) in order to effectively make use of resources and develop defensible nutrient TMDLs for implementation in the Catawba River Basin.With private funding, Systech Water Resources, Inc. (Systech) originally developed a model application for the entire river basin in both North and South Carolina (Completed 2000). Subsequent refinements have been made to the model since that time. Systech and University of South Carolina further enhanced the model (Completed 2003) for the South Carolina portion of the watershed basin. North Carolina Department of Environment and Natural Resources (NCDENR) and Systech provided model updates for North Carolina portion of the Basin (Completed 2004). The model simulation period has also previously been extended in the South Carolina portion to include water quantity and water quality data through 2005 (Completed 2007).

Beginning in October 2012, SCDHEC entered an agreement with Systech to do additional model refinements for the South Carolina portion of the watershed basin. These enhancements are necessary in order to represent current conditions and document model performance. The longer-term goal will be to use the model application to develop defensible nutrient TMDLs in the Catawba River Basin. The scope of work has been broken down into two Phases:

Phase I: Extended the model simulation period by including water quantity and water quality data through 2012. In addition, updated physical landuse characteristics in the model application were needed in order to better account for development changes in the South Carolina portion of the Catawba River Basin since 2000. Some refinements occurred to more accurately characterize contributions from urban, or more developed, areas in the watershed. A review of the overall model calibration, or ability of the model to accurately predict observed conditions, was needed once the initial tasks were completed. Each of these major tasks in Phase I were completed in August 2013. The findings have been documented in a Phase I Memorandum.

Phase II: Based on the findings from Phase I, a scope of work was developed for the next steps. Additional calibration work will be needed for the WARMF model application for both hydrology (water quantity) and water quality. There will be additional refinements to more accurately characterize contributions from urbanized, or urban, areas in the watershed. Systech will then develop a draft calibration report for the South Carolina portion of the WARMF model application. The Department will provide the draft calibrated model and report for stakeholder review in early 2014 and will be requesting comments to be considered in the final model calibration which is scheduled for spring 2014.

Public Meeting November 19, 2013

The S.C. Department of Health and Environmental Control (SCDHEC or the Department) held a public meeting in Rock Hill, SC on November 19, 2013 in order to update Catawba River Basin stakeholders and other interested parties on the status of the most recent model updates. The goal of the meeting was to discuss recent model updates and the next steps as the Department moves forward with nutrient TMDL development. A brief presentation by SCHDEC staff was followed by a question and answer session. A PDF version of the presentation may be downloaded here.

Lower Catawba Basin Nutrient TMDL Model Update
Date/Time: Tuesday, November 19, 2013 3:00pm-5:00pm
Location: Rock Hill City Operations Center, Training Rooms 132 and 133
757 South Anderson Road
Rock Hill, SC 29730

WARMF Model Stakeholder Review

The Model Review Period has now closed.

SCDHEC provided the preliminary WARMF Lower Catawba Basin model calibration for a forty-five day stakeholder review from January 28, 2014 through March 13, 2014. The model calibration is scheduled to be completed in May 2014 and followed by nutrient TMDL development. The preliminary model review period has closed. Comments received indicated a robust stakeholder review. The comments will help improve the model calibration and documentation. A January 2014 version of the model and report remain available (links below); however, SCDHEC is not requesting additional comments at this time. For additional information, contact Mr. Wade Cantrell, Manager, SCDHEC 303(d), TMDL and NPS Section, 2600 Bull Street, Columbia, SC 29201 or e-mail at cantrewm@dhec.sc.gov.

January 2014 Systech Water Resources, Inc. Draft Modeling Report for the WARMF model application may be downloaded here.

Instructions for downloading the model application and installing to your computer have been included in a single Read Me File.The latest version of the Catawba River Basin WARMF model application as documented in the January 2014 Systech Modeling Report may be downloaded here (Compressed .zip file 0.17 GB).

If there are additional questions, interested parties may contact Mr. Wade Cantrell, Manager, SCDHEC 303(d), TMDL and NPS Section at (803) 898-3548 or e-mail at cantrewm@dhec.sc.gov . Interested parties may also contact Mr. Matt Carswell at (803) 898-3609 or at carsweme@dhec.sc.gov regarding the content of this webpage.

WARMF Model and Supplemental Information

June 2013 Systech Water Resources, Inc. Technical Memorandum regarding Support for the Catawba River Basin WARMF model application may be downloaded here.

October 2007 Systech Water Resources, Inc. Technical Support Report regarding the Catawba River Basin WARMF model application may be downloaded here.

January 2005 Systech Water Resources, Inc. Technical Memorandum regarding the North Carolina Portion Catawba River Basin WARMF model application may be downloaded here.

September 2003 University of South Carolina Publication regarding the Catawba River Basin WARMF model application may be downloaded here.

May 2003 Systech Water Resources, Inc. Technical Report regarding recalibration of the Catawba River Basin WARMF model application may be downloaded here.

New!  July 2001  Systech Water Resources, Inc.  User’s Guide to WARMF may be downloaded here.