United States
                          Environmental Protection
                          Office of Water
September 1994
Watershed   Protection:
TMDL  Note   #2
Bioassessment  and  TMDLs
       Why is
 Total Maximum Daily Loads (TMDLs) allocate allowable loads among different
 pollution sources so that appropriate control actions can be taken, water quality
 standards achieved, and human health and aquatic resources protected. To attain
 applicable water quality standards effectively, all sources of pollution to surface
 waters must be considered, including nonchemical stresses such as habitat
 alteration and hydromodification. This requires incorporating evalua|ions of the
 physical and biological components of aquatic ecosystems. Biological
 assessments (bioassessments) are well-suited to identifying aquatic life use
 impairments and evaluating their relative magnitude.

 Bioassessment is the evaluation of ecosystem condition using integrated
 assessments of habitat and biological communities and comparing the results of
 the assessments to empirically defined reference conditions.  Once an
 impairment is'identified, other techniques, such as chemical sampling and
 toxicity testing might be needed to determine the cause(s) of impairment and
 sources of stress so that appropriate mitigation strategies can be designed and
 implemented.  Bioassessments performed through time provide information
 about the ecological integrity (i.e., the condition of an unimpaired ecosystem as
 measured by combined chemical, physical, and biological attributes [Barbour et
 al., 1992]) of the waterbody and can indicate whether pollution control actions ,
 are achieving the biological endpoints that might be specified by a TMDL.
 They are particularly valuable for assessing the effects of physical habitat
 degradation on biological resources.  Bioassessments can lead to substantially  ;
 more accurate water resources assessments by explicitly linking biological and
 physical habitat evaluations with chemical water quality determinations.

 The  TMDL process is a geographically-based approach to preparing load and
 wasteload  allocations for sources of stress that might impair waterbody integrity.1;
 The  geographic nature of this process can be complemented and enhanced by
 using ecological regionalization as part of bioassessment activities.

 Ecosystems with similar spatial patterns can be grouped into ecoregions, which
 can be developed using mapped variables,  such as hydrologic units, land-surface
 form, soil type, potential natural vegetation, and land use.  Naturally occurring
 biotic'assemblages would be expected to differ among ecoregions but to be
 relatively similar within a given region. One of the key tests for determining the
 validity of ecoregions is to establish that variability within regions is less than
 between regions.  The ecoregion concept provides  a geographic framework for
 more efficient aquatic resource management.   A logical result of applying
  regionalization is that similar water quality standards, criteria, and monitoring
  strategies are  likely to be valid throughout a particular ecoregion, but should be
  modified to accommodate differences between regions (Gallant et al., 1989).
  Ecoregionalization provides a means of identifying sites that represent valid
  reference conditions for an entire region for biosurveys and assessments.  This

How can
be used  in the
TMDL process?
 can obviate the need to identify site-specific reference (i.e., minimally impaired)
 locations.  These might not exist in many watersheds affected by urbanization
 and agriculture.

 /.  Identification of Water Quality-Limited Waters that Require  TMDLs

 The first step in the water quality-based approach is to identify  waterbodies that
 do not meet water quality standards after required controls have been installed.
 See Figure 1.  This  requires reviewing water quality standards, evaluating
 monitoring data, and determining whether adequate controls are in place.
 Biological community and habitat impairments are identified by comparing
 biological monitoring data from waters of concern against a reference condition
 (i.e.,"pristine" or minimally impaired waters) (Plafkin et  al., 1989).  The ability to
 complete bioassessments relatively rapidly enables states to meet the biennial
 reporting requirement for a list of waters still needing TMDLs and priority

2.  Priority Ranking and Targeting Listed Waters

For the second step, a state prioritizes its list of waters needing TMDLs and
targets those waters  for development of TMDLs within a specified period.  While
individual states define their own ranking process, the Environmental Protection
Agency (USEPA) has encouraged the adoption of ranking processes that integrate
the pollution control activities in a state with other resource management
programs and  activities that directly or indirectly relate to water quality.
Bioassessment data can be used in the ranking and targeting process to determine
the relative vulnerability or fragility of particular waterbodies as aquatic habitat.
                               USEPA guidance (1991) lists this as a factor
                               states might consider.
            Ecoregionalization in Ohio

   Ecoregtonallzation has been effectively used in Ohio to
   increase the utility of bioassessments for reporting
   under Clean Water Act 305(b).  The development of
   ecoreglons has allowed Ohio to identify previously
   undetected water quality impairment using btocriteria
   and bioassessments.  A comparison of the waterbody
   impairments identified using biocriteria with waterbody
   chemical exceedances based on the Ohio Water
   Quality Standards was performed as part of Ohio's
   1990 305(b) reporting. It showed that biological
   impairment was evident in 49.8 percent of the
   waterbody segments where no ambient chemical water
   quality exceedances were observed (Yoder, 1991).
   Biological and chemical assessments both indicated
   impairment (or lack of impairment) in slightly greater
   than 47 percent of the waterbody segments.  The
   development of ecoregions and subecoregions was
   fundamental to the ability of biological assessments, in
   concert with biocriteria, to generate these results
   (Yoder, 1991; Shepard, 1993),
                               3.  TMDL Development

                               This third step of the TMDL process involves
                               the compilation and analysis of all available
                               data, as well as any modeling that might be
                               needed to prepare a TMDL for the stressor of
                               concern.  TMDLs can and should be developed
                               for nonchemical stressors that are identified
                               through biosurveys  and habitat assessments.
                               For example, biosurveys and habitat
                               assessments are excellent tools for identifying
                               where  damaged riparian zones should be
                               repaired in order to reduce stream temperature
                               and bank erosion in cool and cold-water
                               streams.  These techniques can be useful for
                               indicating where sediment loadings should be
                               reduced to reduce stream channel
                               embeddedness in trout and salmon spawning
                               reaches. They  can also indicate the size of
                               impacted habitat.

      "Identification of threatened
      good quality waters is an
      important part of this
      approach" --
      Bioassessment can
      identify such waters and
      establish reference conditions

     Assessment of aquatic
     life use attainment
     based on
tdfnttftcauon of Water Quallty-
      Llmtted Waters
 Review  wattr quality standards
 Evaluate monitoring data
 Determine If adequate controls
 are In place
                 Assessment of Water QuaiHy-
                    Based Control Actions
               Monitor polnt/nonpolnt sources
               Audit NPS controls for effectiveness
               Evaluate TMDL for protection
               of wattrbody daslgnatad uses
     Prioritization of
     impaired waters is
     best accomplished
     through assessment of
     biological condition
Aquatic life use and
biocriteria are part
of WQ standards
 Bioassessment of
 receiving waters is
 an important link to
 ecological integrity
                             Priority Ranking and Targeting
                          Integrate priority ranking with other
                          water quality planning and management
                          Use priority ranking to target
                          waterbodles for TMDLs
                            Use of bioassessment
                            should be included in the
                            updated plan.
                   Enhanced if ecological
                   regionalization is
                  Implementation of Control
                Update watarquaHtymanagtmant
                Issue water quality-based permits
                Implamant nonpolnt source controls
                (section 319 management plans)
                              Development of Control
                              Actions through TMDLs
                           Apply geographic approach
                           Establish schedule for phased
                           approach, H nacesuary
                           Complete TMDL development
                          BMP selection and siting best accomplished
                          by incorporating bio- and habitat assessment
     Adapted from Flour* 1, Guidance forth* Implementation
     QfWBtorQuality-BuodDadsIon<: Tho TMDL Proem
                                           TMDLs can be
                                           developed for non-
                                           chemical stressors
Figure 1.  Using bioassessment in the TMDL process
                         4.  Implementation of Control Actions

                         After TMDLs are developed, states must choose appropriate control actions, then
                         site and implement them so that specific sources of stress can meet the
                         allocations specified by the TMDL.  Bioassessment and habitat data can be
                         useful for selecting and siting required controls.  For example, bioassessment and

 habitat data might show that a particular stream reach is impaired due, in part, to
 poor habitat conditions and that those conditions are caused by sediment
 originating from streambank erosion upstream.  Reestablishing vegetated riparian
 buffer zones would be a reasonable control action for this case, which would
 have the additional benefits of reducing stream temperature as the vegetation
 matured and increasing the food base for macroinvertebrates because
 allochthonous material would be added to the stream.

 5. Assessment of Water Quality-Based Control Actions

 Bioassessment can be used as,one component of an integrated monitoring
 approach to measure pollutant inputs from point and nonpoint sources following
 implementation of control actions.  For example, bioassessment can be used  to
 determine the biological and habitat effects of a streambank fencing program to
 reduce streambank erosion in agricultural areas or the effects of controls applied
 to combined sewer overflows.  Collection of monitoring data is essential for
 evaluating whether the TMDL that is developed for a waterbody is successful at
 protecting designated use(s).

 Harbour, M.T., J.B. Stribling, and J.R. Karr. 1992. Biological criteria:
 .'   Technical guidance for streams.  Draft.  United States Environmental
     Protection Agency, Office of Science and Technology, Washington, DC.
 Gallant, A.L.,  T.R. Whittier, D.P. Larsen, J.M. Omernik, and R.M. Hughes.
     1989.  Regionalization as a tool for managing environmental resources.
     EPA 600/3-89/060.  United States Environmental Protection Agency,
     Environmental Research Laboratory, Corvallis, OR.
 Plafkin, J.L., M.T. Barbour, K.D. Porter, S.PC Gross, and R.M. Hughes. 1989.
     Rapid bioassessment protocols for use 'in streams and rivers: Benthic
     macroinvertebrates and fish.  EPA 440/4-89/001.  United States
     Environmental Protection Agency, Office of Water, Washington, DC.
Shepard, L.  1993.  Application of biocriteria under sections 303(c) and 303(d) of
     the Clean Water Act.  Memorandum from L. Shepard, Water Quality
     Standards Coordinator, United States Environmental Protection Agency,
     Region 7, to Susan Jackson and George Gibson, United States
     Environmental Protection Agency, Office of Science and Technology.
    January 8, 1993.
USEPA.  1991. Guidance for the implementation of water quality-based
    decisions: The TMDL process. EPA 440/4-91-001. United States
    Environmental Protection Agency, Office of Water Regulations  and
    Standards, Washington, DC.
Yoder, C.O.  1991. Answering some concerns about biological criteria based on
    experiences in Ohio.   In Water Quality Standards for the 21st Century.
    Proceedings of a Conference.  United States Environmental Protection
    Agency, Office of Water.
                       Any Questions or Comments?  Please, contact Theresa Tuafio, Watershed
                       Branch, Office of Water, U.S. Environmental Protection Agency, 401 M
                       Street SW, Washington, DC 20460, phone 202/260-7079, fax 202/260-7024.