Falls Lake Nutrient Strategy
The Falls Lake Rules are a nutrient management strategy designed to restore water quality in the lake by reducing the amount of pollution entering upstream. Restoration and protection of the lake is essential because it serves as a water supply for many communities, as well as a popular recreation area. However, nutrient-related pollution has caused water quality problems in Falls Lake. Since 2008, the reservoir has exceeded the state’s chlorophyll-a standard, which measures the impacts of nutrient pollution on the lake. The Falls Lake Nutrient Management Strategy was implemented in 2011 to reduce nutrient inputs to the lake from wastewater discharges, stormwater runoff from new and existing development, and agricultural sources. Also known as the Falls Lake Rules, the strategy was developed through extensive water quality modeling and input from stakeholder groups in the watershed.
The Falls Lake rules require all major sources of nutrients in the watershed to reduce their nitrogen loads by 40% and phosphorus loads by 77%. The Falls rules are being implemented in a staged process. Stage I runs through 2020, with the objective of meeting water quality standards in the lower lake, and reducing most nutrient inputs by half across the whole lake. Stage II calls for additional reductions in the upper watershed, with the overall goal of achieving all reductions by 2041.
Falls Lake Rules 2010 Fiscal Analysis
Falls Lake Hearing Officer's Report - November 2010
Falls Lake Watershed Map (jpg)
For the following maps, download files to your computer and unzip using GIS:
Falls Lake Watershed Shapefiles
Session Law 2016-94 established the NC Policy Collaboratory and directed it to oversee the funding of studies of the Falls nutrient management strategy, and to provide recommendations to the EMC to guide further rulemaking. Subsequent session law (S.L. 2018-5) revised the due date for the Collaboratory’s Final Falls Study Report to December 2023. It also extended the deadline for beginning the Falls rules readoption process to December 31, 2024 and extended the implementation of the Falls Stage I rule requirements until the rules are readopted.
NC Policy Collaboratory – Falls Lake Study
Through the Collaboratory, researchers began conducting Falls Lake and watershed studies in 2019. This collection of research projects synthesizes interdisciplinary analysis of Falls Lake’s nutrient content and fluctuation, the factors that affect it, mitigation strategies and their effectiveness, and financial implications of proposed processes. The Collaboratory’s Falls Lake Study Final Report was completed and submitted to the Environmental Management Commission on December 20, 2023. The individual research reports can also be found on the NC Policy Collaboratory website.
Upper Neuse River Basin Association (UNRBA) Falls Lake Monitoring Project
The UNRBA conducted major efforts following adoption of the Falls Lake rules to address the scientific uncertainty of the nutrient reduction strategy and its underpinning water quality models. They collected additional water quality data at least monthly between August 2014 and October 2018 from 38 tributary stations in the Falls watershed as part of a $3.5 million member-funded Monitoring Project. This project was designed to support their remodeling of the lake and watershed, development of alternative regulatory targets as appropriate, and to inform re-examination of the Falls Lake Rules. The data from this monitoring project was used to gain more detailed understanding of the lake’s physical, chemical, biological, and geological characteristics. The results of the UNRBA Falls Lake Monitoring Project are presented in the 2019 Final Monitoring Report.
Upper Neuse River Basin Association Falls Lake Modeling Project
The UNRBA developed three different models for Falls Lake. The Watershed Risk Management Framework (WARMF) to conduct watershed and lake modeling. The Environmental Fluid Dynamics Code (EFDC) as a more complex lake model and a statistical/Bayesian model to evaluate uses of the lake. The UNRBA’s Final Watershed Model Report was submitted to DWR in December 2023. The UNRBA’s Final Lake Model Report (includes the Lake WARMF, Lake EFDC, and Lake Statistical models) was submitted to DWR in December 2024.
More Information
For information about the Falls Lake Nutrient Strategy rules and the rule readoption process, please subscribe to the Falls Lake Listserv or email John Huisman at john.huisman@deq.nc.gov.
15A NCAC 02B .0275 - Purpose and Scope
15A NCAC 02B .0276 - Definitions
15A NCAC 02B .0277 - Stormwater Management for New Development
15A NCAC 02B .0278 – Stormwater Management for Existing Development
15A NCAC 02B .0279 – Wastewater Discharge Requirements
15A NCAC 02B .0280 – Agriculture
15A NCAC 02B .0281 – Stormwater Requirements for State and Federal Entities
15A NCAC 02B .0282 - Options for Offsetting Nutrient Loads
15A NCAC 02B .0235 – Amended Neuse River Basin Stormwater Requirements
15A NCAC 02B .0315 – Amended Neuse River Basin
The Falls rules require the Division of Water Resources to report to the Environmental Management Commission on specific aspects of progress in the Falls Lake watershed in January 2016 and every five years thereafter. This report satisfies that requirement by providing an update on implementation of the rules, evaluating changes in nutrient loading to the lake, detailing progress towards achieving the chlorophyll a water quality standard, and characterizing advances in scientific understanding and control and accounting technologies while identifying future research and data needs.
The Falls Lake Rules were approved by the N.C. Rules Review Commission at their Dec. 16, 2010 meeting. The rules were approved with an effective date of Jan. 15, 2011. The final approved rules are provided above.
New Development Stormwater Programs
The Falls New Development rule required the Division to develop a New Development Model Program to assist local governments in developing their local programs. The NC Environmental Management Commission approved the Division of Water Resource's Model Program on march 10, 2021. The Model Program contains a Model Ordinance and a Nutrient Loading Accounting Tool.
All local governments int he Falls Lake watershed adopted and began implementing local stormwater programs in July 2012.
Stormwater Accounting Tool
The Falls Rules require that the Division develop a Nutrient Load Accounting Tool to estimate nutrient loads from new development, and changes in loads due to use of Stormwater Control Measures. The Jordan/Falls Lake Stormwater Nutrient Load Accounting Tool version 2.0 has been recently replaced by a greatly improved version of the Tool known as the Stormwater Nutrient and Phosphorus Tool, or SNAP (version 4.0). The new tool and accompanying User’s Manual can be downloaded from the NPS Nutrient Practices and Crediting page.
Results calculated using version 2.0 of the Tool were accepted by local permitting programs or the Division for meeting nutrient export calculations through January 1, 2018. SNAP Version 4.0 is now the appropriate tool to use.
Existing Development Stormwater
The Falls Lake Existing Development Rule requires local governments to develop and implement load reduction programs to reduce nutrient loading from existing developed lands under their control in the watershed. Implementation is divided into two stages, with Stage I calling for reductions in loading back to 2006 baseline levels, and additional reductions called for in Stage II that require all major sources of nutrients in the watershed to reduce their nitrogen and phosphorus loads by 40 and 77 percent from baseline levels, respectively.
In 2020, the Division completed the development of a revised model program that affected parties could use to guide development of their mandated load reduction programs. This model program was developed with input from the regulated community and approved by the Commission at its January 2021 meeting.
Falls ED Model Program – Approved January 2021
Catalog of Nutrient Reduction Practices
UNRBA Interim Alternative Implementation Approach (IAIA) Joint Summary Report - 2022
UNRBA IAIA Joint Summary Report - 2023
NCDOT Falls Lake Stormwater Management Program
The Falls Lake nutrient management strategy requires NCDOT to develop and implement a Stormwater Management Program for all new developmentand existing development activities. The NCDOT Stormwater Management document was approved by the January 2014 EMC. It describes NCDOT’s Stormwater Management Program for New and Existing Development, which addresses nutrient runoff from new and widened roads, new non-road development, and existing road and non-road development in the Falls Lake Watershed.
NCDOT Falls Stormwater Management Program
Agriculture
The purpose of the Falls Lake Watershed Oversight Committee (WOC) is to guide the implementation of the Agriculture Rule. This committee is charged with developing tracking and accounting methods for nitrogen and phosphorus loss from agricultural land in the Falls Lake Watershed. The Agriculture Rule was adopted in January 2011, members of the committee were appointed by the Division of Water Quality in Summer 2011, and the committee began meeting in August 2011. The WOC submitted an initial accounting report to the EMC in March 2013 followed by their first annual report in January 2014.
DWR and its partners actively monitor water quality in the Falls Lake watershed and routinely assess its performance against existing water quality standards.
Falls and Jordan Lakes Monitoring Page
See also:
DWR Monitoring Coalition Program
DWR Intensive Survey Branch
DWR Modeling and Assessment Branch
DWR Ecosystems Branch
North Carolina 303(d) list
Falls Lake Rules Information:
John Huisman, 919-707-3677 or john.huisman@deq.nc.gov
Rich Gannon, 919-707-3673 or rich.gannon@deq.nc.gov
Falls Watershed Buffer Information:
Stephanie Goss, 919-707-9013 or stephanie.goss@deq.nc.gov