Nutrient Limits: What to Expect. Water Division Arkansas Department of Environmental Quality

Transcription

1 Nutrient Limits: What to Expect Water Division Arkansas Department of Environmental Quality

2 Timeline of Nutrient Criteria Development 1998 EPA published the National Strategy for the Development of Regional Nutrient Criteria (National Strategy) 2000 EPA published Nutrient Criteria Technical Guidance Manual: Rivers and Streams 2001 EPA published recommended, regional numeric nutrient criteria for rivers and streams under section 304(a) of the Clean Water Act (66 FR 1671).

3 Timeline of Nutrient Criteria Development 2001 EPA requested each state and authorized tribe to develop a Nutrient Criteria Development Plan 2004 ADEQ updated Reg Nutrients Materials stimulating algal growth shall not be present in concentrations sufficient to cause objectionable algal densities or other nuisance aquatic vegetation or otherwise impair any designated use of the waterbody. Because nutrient concentrations do not always correlate directly with stream impairments, impairments will be assessed by a combination of factors such as water clarity, dissolved oxygen, ph, aquatic-life community structure and possibly others.

4 Timeline of Nutrient Criteria Development

5 EPA Guidance for Criteria Development 2000 EPA Nutrient Criteria Technical Guidance Manual: Rivers and Streams Approach 1 Use reference stream conditions -Assumes a large portion of streams are impaired Approach 2 Predictive models -Difficult to replicate across ecoregions Approach 3 Established nutrient thresholds, biocriteria, and stressor-response relationships -Most defensible

6 EPA Guidance for Criteria Development Approach 1 Set criteria at 25 th percentile of all data OR 75 th percentile of reference streams - Nutrient Concentration + More involved, based on reference conditions, preferred method Difficult to define least-disturbed conditions, thus use <25 th percentile as least-disturbed

7 EPA Guidance for Criteria Development Approach 3 (Development of Biocriteria) Based on the assumption that as nutrient concentrations increase, certain biological assemblages will be negatively impacted Develop Nutrient Index of Biotic Integrity (N-IBI) Allow ADEQ scientists to identify any potential relationships between nutrient concentrations and biotic assemblages If relationships exists, ADEQ scientists will then attempt to determine at what point biotic assemblages are negatively impacted (thresholds) These thresholds can be used to set numeric criteria along with values from Approach 1

8 Approach 3 (Concept of Stressor-Response)

9 Approach 3 (Concept of Stressor-Response)

10 Approach 3 (Hypothetical Stressor-Response)

11 Nutrient Criteria Development Lakes/Reservoirs Pilot Project Beaver Lake Growing season geometric mean chlorophyll a 8 ug/l Secchi depth 1.1m - Type B and C Lakes Rivers/Streams Pilot Project Upper Saline River Watershed Ozark ERW

12 Reg Nutrients (B) Site Specific Nutrient Criteria Lake Chl a (ug/l)** Secchi (m)*** Beaver Lake* * These criteria are for measurement at the Hickory Creek site over the old thalweg, below the confluence of War Eagle Creek and the White River in Beaver Lake. ** Growing season geometric mean (May October) *** Annual Average

13 Classification and Validation of Nutrient Criteria within the Ozark Highlands ERWs Task 1 Historical Data Compilation and Site Selection

14 Task 2 Data Collection Subtask 2.1 Water Quality Assessments Anticipated time frame: 2013 & 2014 A minimum of twelve collections made over two years Collect in-situ parameters during each site visit Water chemistry Total Kjeldahl Nitrogen (TKN), total organic carbon (TOC), ammonia nitrogen (NH4-N), total dissolved solids (TDS), Nitrite + Nitrate Nitrogen (NO2+NO3-N), turbidity, total phosphorus, total, nitrogen, total suspended solids (TSS), orthophosphorus, and metals Diurnal dissolved oxygen assessments Deploy continuous read meters twice during critical season

15 Task 2 Data Collection Subtask 2.2 Macroinvertebrate Assemblage Assessment Anticipated time frame: Spring (February-April) 2013 & 2014 Collect using five-minute traveling kick methodologies described in ADEQs macroinvertebrate SOP Subtask 2.3 Periphyton Assemblage Assessment Anticipated time frame: Spring, Summer 2013 & 2014 Ash Free Dry Mass (AFDM) and Chlorophyll a -Periphyton assemblages will be sampled following surface area methods. A quantitative algal subsample will be collected from ten randomly selected cobbles at each riffle location.

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18 Approach 1 Ozark Highlands 5 th 25 th 75 th* EPA 2001 Total Nitrogen (mg/l) Total Phosphorus (mg/l) *75 th percentiles calculated from least-disturbed streams ERWs 5 th 25 th 50 th 75 th EPA 2001 Total Nitrogen (mg/l) Total Phosphorus (mg/l)

19 Status of Nutrients Across the Country As of 2008* - 7 states have adopted numeric criteria for one or more parameters for at least one entire waterbody - 18 states adopted numeric criteria for one or more parameter for select individual waters - Arkansas proposed Beaver Lake criteria in states have not adopted any numeric criteria *EPA-821-F State Adoption of Numeric Nutrient Standards ( )

20 What does all this mean? Permit Limits based defensible science Currently use Reg As well as location, i.e. Nutrient Surplus Area

21 Reg Nutrients

22 Will I get a new limit?

23 To protect, enhance, and restore the natural environment for the well-being of all Arkansans.