Bioassessment Program

Since 2000, the Bioassessment Program has conducted annual bioassessments throughout all of Nevada to evaluate on the ecological integrity of Nevada’s wadeable streams and rivers. Ecological integrity can be defined as the capability of a surface water to support and maintain a balanced, integrated community of organisms having a species composition, diversity and functional organization comparable to that of the natural habitat of the region. It is determined by monitoring the biological condition, water quality and physical habitat. Assessing biological condition of a waterbody includes analyzing the community composition of benthic macroinvertebrates and periphyton as well as documenting the condition of the riparian habitat. Evaluating water quality includes field measurements of dissolved oxygen, pH, conductivity and water temperature as well as independent laboratory analysis of water column chemistry. Describing the physical habitat includes assessing stream channel characteristics such as substrate, bank stability, depth and flow. All three of the above indicators – biological condition, water quality and physical habitat – are integral in the evaluation of the overall ecological integrity of Nevada’s wadeable streams and rivers.

The program works to achieve the following objectives:

· Evaluate, through monitoring, the biological condition, water quality, and physical habitat of wadeable streams and rivers throughout the State. This is accomplished through the comparisons of probabilistic, reference, targeted and repeat site data and conditions.

· Support the development of water quality standards (WQS) and total maximum daily loads (TMDLs) through bioassessments. This is accomplished by collaborative efforts with the Standards and Monitoring Program through routine assessments, expanded surveys and special investigative projects as designed by the BWQP staff.

· Investigate through bioassessments streams and rivers of concern, identified by the BWQP’s 303(d)/305(b) Integrated Report and/or interested parties, to evaluate if WQS and beneficial uses are being met and to determine if ecological integrity indices confirm or refute areas of concern. This is accomplished by performing one or more bioassessments of the site of concern, corroborating WQS, determining the progress of TMDLs and utilizing the results to determine a causal analysis of impairment (if present).

· Document and describe, through data analysis, data maintenance and reporting, the condition of Nevada’s wadeable streams and rivers. This is accomplished by the analysis of field data, independent analytical results of water chemistry, benthic macroinvertebrates and periphyton, and consolidating collected information into reports and presentations for internal and external parties.

In addition to the Nevada-specific bioassessment samplings, the Bioassessment Program participates in the EPA’s National Aquatic Resource Surveys (NARS). The NARS are a five-year rotating cycle of aquatic assessments include lakes, rivers and streams, and wetlands. The results from the NARS assessments contribute to a nation-wide report on aquatic resources presented Congress. More information on the NARS program can be found here.

The Bioassessment Program also regularly participates in educational events, workshops and conferences to share the results of Nevada’s bioassessments with the public and scientific community.

The Nevada Quality Assurance Program Plan (QAPP) for the Bioassessment Program establishes specific quality requirements for the collection and management of the bioassessment data.

For more information on the Bioassessment Program or to request taxonomic data, contact dentonm [at]

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