Why Biological Monitoring?
Nebraska has over 81,000 miles of streams of which approximately 18,000 miles flow continuously. Streams in Nebraska are capable of containing a rich diversity of aquatic life including macroinvertebrates (i.e. small animals living in water that can be seen with a naked eye), fish, amphibians, and mammals. However, these streams are also potentially impaired from a large variety of impacts, including excess nutrients, pesticides, sedimentation, habitat degradation, and others.
The aim of the Stream Biological Monitoring Program (SBMP) is to use the health of the living communities within streams to inform us of when these impacts have caused streams to become unhealthy. Accurate biological assessments are vital tools for stream management and restoration.
History of the Stream Biological Monitoring Program
The Department began biological monitoring in 1983 with a targeted approach for classifying stream segments for Title 117 (Nebraska Surface Water Quality Standards). Over 900 stream sites were sampled for fish and macroinvertebrates over a 14 year period. In 1997, the Department added a probabilistic monitoring design that involved the sampling of randomly selected sites to the SBMP in order to address statewide and regional questions about water quality. Data to answer such questions as “How good is the water quality in Nebraska?” is best obtained from sample locations chosen so that all streams have an equal chance of being sampled.
These monitoring sites are generated by a computer program that randomly chooses sites on streams throughout Nebraska. From 1997-2020, the biological communities of more than 1000 stream sites have been sampled.
Where is the Monitoring Conducted?
Each year 34-40 randomly selected wadeable stream sites (i.e. streams that are shallow enough to sample without boats) are chosen for study in two or three river basins throughout Nebraska. During a six-year cycle, all 13 major river basins in the state are intensively monitored (see map above for basin divisions).
What is Monitored?
Aquatic macroinvertebrates are small creatures that live in streams attached to rocks, vegetation, or woody debris, or burrowed into the stream bottom. They include aquatic larval stages of insects such as mayflies and dragonflies; crustaceans such as crayfish and clams; and worms and snails.
Because they are extremely sensitive to pollutants, macroinvertebrate populations often respond predictably to changes in water quality. Department personnel have collected nearly 600 different species of macroinvertebrates (and many others identifiable only at higher taxonomic levels such as family and genus) through the sampling effort associated with the SBMP. In addition, numerous new species not previously found in Nebraska have been recorded.
From small coldwater trout streams to large warm rivers, Nebraska streams support more than 70 species of fish. As with macroinvertebrates, fish display varying habitat requirements and water quality tolerances making them excellent indicators of stream health. The majority of Nebraska’s species are small, with adults generally less than 5 inches long. The Department’s fish surveys have also provided information on changing abundances and ranges of fish in the state. Some species have been found to occur in many more places than previously thought, while others have shown dramatic declines over the last 30 years.
How are the Data Used?
NDEE calculates “metrics” from the biological data, which are measurements of specific properties. For example, the fish metrics used to determine stream quality include the number of different fish families present, the percentage of pollution tolerant fish, the number of benthic species, the number of lithophilic (rock-associated) species, and the percentage of nesting species. For macroinvertebrates, NDEE uses the number of unique macroinvertebrates, the number of sensitive species, the percentage of pollution tolerant species, the number of grazing (herbivorous) species, Shannon-Weiner diversity, and the family-level Hilsenhoff Biotic Index. The biological data collected through the SBMP are used to inform a variety of management activities, such as:
- Documenting current statewide biological conditions in Nebraska’s streams to track water quality status and trends.
- Identifying streams that do not attain their assigned environmental goals and are in need of restoration or remedial action. Where significant problems were found (i.e. streams were assessed as having poor biological conditions), these stream segments are placed on the 303(d) List of Impaired Water Bodies (as required by the federal Clean Water Act) with regard to aquatic life.
- Identifying exceptional stream segments (reference conditions).
- Providing accurate biological distribution information.
Under the federal Clean Water Act, states are required to develop programs to evaluate the physical, chemical, and biological integrity of the Nation’s waters and to adopt water quality standards to restore and maintain that integrity. States must report to Congress on the condition of all waters within their boundaries every two years. The information collected by the Department’s SBMP satisfies these requirements for assessing the biological integrity of Nebraska’s streams.
For More Information
The 2018 and 2019 Nebraska Water Monitoring Programs Report