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Water Quality Standards

• Water Quality Standards Regulations: Louisiana

• Title 33 Environmental Regulatory Code - Part IX Water Quality, Chapter 11 Surface Water Quality Standards

Designated Aquatic Life Uses

Louisiana uses multiple thresholds and use categories to protect aquatic life:

• Designated Uses for Protection of Aquatic Life
  • Fish and Wildlife Propagation – the use of water for aquatic habitat, food, resting, reproduction, cover, and/or travel corridors for any indigenous wildlife and aquatic life species associated with the aquatic environment. This use also includes the maintenance of water quality at a level that prevents damage to indigenous wildlife and aquatic life species associated with the aquatic environment and contamination of aquatic biota consumed by humans. The use subcategory of limited aquatic life and wildlife recognizes the natural variability of aquatic habitats, community requirements, and local environmental conditions.
  • Limited aquatic life and wildlife use may be designated for water bodies having habitat that is uniform in structure and morphology, with most of the regionally expected aquatic species absent, low species diversity and richness, and/or a severely imbalanced trophic structure. Aquatic life able to survive and/or propagate in such water bodies includes species tolerant of severe or variable environmental conditions. Water bodies that might qualify for the limited aquatic life and wildlife use subcategory include intermittent streams, and naturally dystrophic and man-made water bodies with characteristics including, but not limited to, irreversible hydrologic modification, anthropogenically and irreversibly degraded water quality, uniform channel morphology, lack of channel structure, uniform substrate, lack of riparian structure, and similar characteristics making the available habitat for aquatic life and wildlife suboptimal.
• Designated Use for Protection of Fishery-based Resources
  • Oyster Propagation – the use of water to maintain biological systems that support economically important species of oysters, clams, mussels, or other mollusks so that their productivity is preserved and the health of human consumers of these species is protected. This use designation shall apply only to those water bodies specifically so designated in LAC 33:IX.1123, Table 3 and not to their tributaries or distributaries unless so specified.
• Some Aquatic Life and/or Fishery-based resources may be protected through the designation of a stream as an Outstanding Natural Resource Water (ONRW)
  • Outstanding Natural Resource Water – ONRWs are water bodies designated for preservation, protection, reclamation, or enhancement of wilderness, aesthetic qualities, and ecological regimes, such as those designated under the Louisiana Natural and Scenic Rivers System or those designated by the department as waters of ecological significance. Characteristics of outstanding natural resource waters include, but are not limited to, highly diverse or unique instream and/or riparian habitat, high species diversity, balanced trophic structure, unique species, or similar qualities. This use designation shall apply only to those water bodies specifically so designated in LAC 33:IX.1123, Table 3 and not to their tributaries or distributaries unless so specified.

Biological Criteria
__X__ Narrative statement
_____ Numeric
_____ No criteria

LAC 33:IX, 1113.B.12. Biological and Aquatic Community Integrity
a. The biological and community structure and function in state waters shall be maintained, protected, and restored except where not attainable and feasible as defined in LAC 33:IX.1109. This is the ideal condition of the aquatic community inhabiting the unimpaired water bodies of a specified habitat and region as measured by community structure and function. The biological integrity will be guided by the fish and wildlife propagation use designated for that particular water body. Fish and wildlife propagation uses are defined in LAC 33:IX.1111.C. The condition of these aquatic communities shall be determined from the measures of physical, chemical, and biological characteristics of each surface water body type, according to its designated use (LAC 33:IX.1123). Reference site conditions will represent naturally attainable conditions. These sites should be the least impacted and most representative of water body types. Such reference sites or segments of water bodies shall be those observed to support the greatest variety and abundance of aquatic life in the region as is expected to be or has been recorded during past surveys in natural settings essentially undisturbed by human impacts, development, or discharges. This condition shall be determined by consistent sampling and reliable measures of selected, indicative communities of animals (i.e., fish, invertebrates, etc.) and/or plants as established by the department and may be used in conjunction with acceptable chemical, physical, and microbial water quality measurements and records as deemed appropriate for this purpose.     ​

Antidegradation Policy
Biological resources are specifically identified for protection through narrative statements in Louisiana’s antidegradation policy (LAC 33:IX.1119); specific biocriteria or bioassessment methods are not included in the antidegradation implementation plan outlined in LAC 33:IX.1119.

Biological Assessment

What biological assemblages are used in the bioassessment program?
None.

Are bioassessments used to support 303(d) listings?
No.

How are assemblages used to make impairment decisions?
Not applicable.

Other uses of biocriteria or bioassessment within the water quality program:
Biological data are being used to inform non-303(d) assessment efforts, including evaluation of resource injuries and for planning restoration efforts. Biological data have also been used in special studies such as those conducted under the USDA Mississippi River Basin Initiative (MRBI).

Technical Support Information and Documents:

Reference condition:
LDEQ has identified reference sites within several ecoregions in the state. Conditions at these least-impacted reference sites aid in demonstrating natural background water quality and ecological conditions found in Louisiana.   

Technical reference material:
Water Quality Standards; Data Evaluation, Assessment, and Review; and Data Management

Biocriteria:
Not available.

Stressor identification/causal analysis approach:
LDEQ has conducted special studies to collect data to evaluate stressor-response approaches within rivers and streams in inland ecoregions in the state. Results of this evaluation may aid in determining relationships of stressor and response variables in rivers and streams in inland ecoregions of Louisiana.

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