Monthly Archives: November 2016

Site Specific Nutrient Criteria Approved for Beaver Lake

by: Angela Danovi, Program Director of Beaver LakeSmart

On November 10, 2016, ADEQ announced the EPA completed its review of the Arkansas Regulation 2, which establishes water quality standards for surface waters throughout the state of Arkansas. As part of the review process, EPA approved most of the proposed revisions to the regulation including adopting site specific criteria on Beaver Lake. The provision found in section 2.509, Nutrients, states the site-specific criteria to be:

  • Growing season geometric mean of chlorophyll a concentration: 8 µg/L
  • Annual Average of Secchi transparency: 1.1 meters

For measurement at Hickory Creek site over the thalweg, below the confluence of War Eagle Creek and the White River in Beaver Lake.


In the sections below we have tried to answer basic questions for you about the new nutrient criteria regulations on Beaver Lake.  

How did we get here?

In responding to a 2001 EPA policy requiring all states to develop numeric nutrient criteria to protect the designated uses of waterbodies within each state, ADEQ set about the process of developing and implementing site specific numeric water quality criteria for all Arkansas lakes and reservoirs with a goal of setting lake and reservoir criteria by 2010. Development of the newly adopted and approved Beaver Lake criteria began in 2005 when ADEQ established the Beaver Lake Scientific Workgroup comprised of members representing ADEQ, AWRC, USGS, Beaver Water District, CH2MHILL, City of Fayetteville, FTN Associates, Ltd., and Dr. Joe Nix. The purpose of the Beaver Lake Scientific Workgroup was to jointly develop sound, scientifically based numeric water quality criteria to protect the Beaver Reservoir for all its designated uses. In 2008, FTN Associates, Ltd. published the “Beaver Lake Site-Specific Water Quality Criteria Development: Recommended Criteria” report, which made the recommendations of the site-specific criteria recently approved by EPA.

In developing the criteria, a weight of evidence approach was used which included considerations of:

  1. Surrounding state criteria for chlorophyll, Secchi, TP, TN
  2. EPA ecoregion values
  3. Percent values of reference and extant for Beaver Lake
  4. Hydrologic plunge point analyses
  5. Statistical analyses for Beaver and reference lakes
  6. Empirical nutrient loading relationships
  7. Dynamic modeling

In 2013 ADEQ undertook a required triennial review of its water quality standards.  Public listening sessions were held and public comments were taken regarding the entirety of regulation 2.  The same year, the Arkansas Pollution Control and Ecology Commission adopted the site-specific nutrient criteria recommendations for Beaver Lake.  Those recommendations were submitted to EPA alongside other recommended changes and updates.  EPA issued their ruling accepting the site-specific nutrient criteria recommendations on October 31, 2016.

What are we protecting?

The purpose of any water quality standard is protecting the designated uses of that water body. Under the Arkansas Water Quality Standards, the designated uses for Beaver Lake are:

  1. primary contact recreation (swimming);
  2. propagation of fish, wildlife and aquatic life; and domestic,
  3. industrial, and agricultural water supply (drinking water).

In general, domestic water supply represents the highest priority use for Beaver Lake and is associated with the most stringent water quality standards. Therefore, water quality criteria development initially focused on protecting this designated use.



What is Secchi Transparency?

Secchi Transparency readings come from measuring water clarity using a secchi disk.  A Secchi Disk is an easy to use device that is lowered into the water to measure the water’s transparency or clarity.



What is Chlorophyll a?

Chlorophyll a is a pigment found in algae. It is essentially what makes algae green.  Scientists use chlorophyll a concentrations to measure algal population density in waterbodies like Beaver Lake.


Why are Chlorophyll and Secchi transparency important?

The criteria approved for Beaver Lake were designed to limit the amount of nutrients, phosphorus and nitrogen in the lake. However, the chlorophyll and Secchi transparency mean values are considered conservative and protective of the designated uses without imposing overly onerous phosphorus and nitrogen criteria, which are less connected to the designated of the lake. Chlorophyll a and Secchi transparency can affect aquatic life, drinking water treatment and costs, and recreation. Additionally, Chlorophyll is an important indicator of water quality because increased chlorophyll concentrations are associated with increased risk of blue-green bacteria algae blooms that can negatively affect drinking water supplies. Carcinogenic compounds can be formed from organic matter during disinfection of drinking water. Organic carbon found in raw water, including algal cells and organic compounds released by algae, can react with chlorine during treatment to form these compounds. While there are treatment procedures that can reduce the formation of these compounds, the procedures increase drinking water treatment costs.  Limiting Chlorophyll a in Beaver Lake ensures a safe, reliable, and affordable drinking water source for everyone.


Why was Hickory Creek selected as the location to be monitored?

Several factors went in to identifying the Hickory Creek site as the location for establishing the site-specific criteria on Beaver Lake. Advantages of the Hickory Creek site include accessibility due to the presence of a boat ramp at the location, the site is below the confluence of all three major tributaries and should integrate the loadings from these three tributaries, and it is upstream from the location of a major drinking water intake, so it should provide protection from episodic excursions of chlorophyll and suspended sediment in the transition zone.

How will this new regulation affect me?

There is not a direct impact to individual landowners and watershed residents. The new standards will affect permits to discharge wastewater in the lake’s watershed, meaning as existing and new permits are approved in the watershed, consideration of this regulation must be considered. Additionally, the regulation serves the purpose of protecting the water quality based on the designated uses of the lake. In an interview to the Northwest Arkansas Democrat Gazette published on November 13, 2016, Dr. Bob Morgan of Beaver Water District said, “The lake is not receiving the protection of the standard that we hoped that it would have. It’s not keeping us from doing anything…if an issue popped up and the standard was in place, then there’s a mechanism in state law that starts toward getting the issues worked out.” Thus far, communication and voluntary incentives have helped to prevent major problems in Beaver Lake. Voluntary action will continue to be a major component of engaging everyone in protecting our lake and watershed.

What’s next?

On July 14, 2014 ADEQ reconvened the Beaver Lake Scientific work group to address remaining questions associated with assessment methodology.  These questions include:

  1. defining sample collection methods for chlorophyll a,
  2. ensuring representative samples of actual lake conditions,
  3. other potential assessment methods.

To ensure accurate assessment methodology the Beaver Watershed Alliance in partnership with the Washington County Farm Bureau, CH2MHILL, the City of Fayetteville, and the Beaver Water District commissioned a three phased, two year project with the University of Arkansas Water Resources Center to accomplish the following:

  1. derive an initial assessment methodology based on the methods used to develop the site specific numeric criteria for chlorophyll-a and Secchi Transparency in Beaver Lake
  2. Asses the variation in chlorophyll a and Secchi transparency across multiple spatial and temporal scales in order to validate the assessment method, and
  3. quantify trends in chlorophyll a, Secchi Transparency, and nutrient concentrations in Beaver Lake and the major inflowing rivers to verify any potential water quality impairment.

The first report, “Evaluating the Assessment Methodology for the Chlorophyll-a and Secchi Transparency Criteria at Beaver Lake, Arkansas ” was completed in 2015.

The assessment methodology is a separate document that also must receive EPA approval. The ADEQ appointed workgroup will be meeting through December of this year to provide recommendations on assessment methodology for regulation 2.