Nutrient Criteria Development Update Emily McArdle Nutrient Criteria Coordinator | Water Quality Standards Group |

Current Standards: General Criteria § General Criteria §307.4(e) Nutrients. Nutrients from permitted discharges or other controllable sources must not cause excessive growth of aquatic vegetation that impairs an existing, designated, presumed, or attainable use. Site-specific nutrient criteria, nutrient permit limitations, or separate rules to control nutrients in individual watersheds are established where appropriate after notice and opportunity for public participation and proper hearing. Site-specific numeric criteria related to chlorophyll a are listed in Appendix F of § of this title.

Current Standards: Site Specific Uses and Criteria Site-Specific Uses and Criteria §307.7(B)(4)(E) Nutrient criteria. Numeric and narrative criteria to preclude excessive growth of aquatic vegetation are intended to protect multiple uses such as primary, secondary, and noncontact recreation, aquatic life, and public water supplies. Nutrient numeric criteria for specific reservoirs, expressed as concentrations of chlorophyll a in water, are listed in Appendix F of § of this title.

EPA and Numerical Nutrient Criteria 1998 EPA mandate: Numerical Nutrient Criteria by 2004 Allowed state development plans and schedules Submitted plans to EPA in 2001, 2006, plan still pending EPA approval Proposed Chronology: reservoirs, estuaries, streams and rivers Set on historical conditions

NCDAWG Survey and Responses Support of weight of evidence approach for reservoir assessment Parameters to include TN, TP, Chlorophyll a, as well as DO and transparency (Secchi depth) Strong preference for site specific criteria Emphasis on ambient conditions over literature values Similar comments on estuary criteria development Encouraged considering a multitude of parameters and to create site specific criteria rather than grouping bays Many gave specific model recommendations

Reservoir Nutrient Criteria Adopted standalone Chlorophyll a criteria 75 reservoirs in 2010 EPA approved criteria for 39 of the 75 reservoirs Presented assessment protocol to address reservoirs with disapproved criteria and to integrate confirmatory parameters in July 2015 Received written comments from City of Austin, Tischler/Kocurek, LCRA, TPWD, BRA, SRA, TRWD. Thank you for your input! When method is finalized, SWQM Assessment Guidance will be updated

Estuaries contract: Texas A&M University Principal Investigators: Dr. Dan Roelke and Dr. Antonietta Quigg Relationships between inflows, nutrient loading, phytoplankton and dissolved Oxygen: A numerical modeling study San Antonio and Copano Aransas Bay System Data rich systems with reduced inputs Statistical analysis of historical data for SAB and CABS will guide the biological nodules nested within circulation models Identify inflow and nutrient loading thresholds

Streams and Rivers contract: Texas Institute for Applied Environmental Research Principal Investigator: Dr. Larry Hauck Periphyton collection in streams, building upon dataset from similar 2011 contract Periphyton collection method refinement Collecting paired water quality and biological data Analyzing the physiochemical, periphyton, habitat, and flow data

Questions and other considerations? Emily McArdle