Regulated River Reaches

Most large rivers in the northern hemisphere are no longer free flowing and it has been estimated that 60% of the world's total stream flow is likely to be regulated by the year 2000.  Heightened public awareness of the effects of dams on aquatic biodiversity and on ecosystem function has made rehabilitation of regulated rivers a management and research priority.  Changes in physical habitat - most often water temperature - is the primary factor responsible for the large declines in fish and invertebrate biodiversity that normally follows dam construction.
Impacts	Large fluctuations in discharge over short time period can flush organisms downstream or strand them in dewatered areas.  Lack of seasonality in streamflow water temperatures can make life too unpredictable for many organisms. Dams also create barriers to fish migration.
Hydrology	Discharge regime - highly variable, daily and seasonal fluctuations are generally outside the realm experienced by natural streams. Temperature - rivers downstream from hypolimnion release dams are usually less variable than pre-dam conditions, winter temperatures are generally warmer and summer temperatures are colder than pre-dam.
Instream habitat	Large substrate with abundant algae and aquatic plant growth.  Substrate particles can be embedded into the stream bed by fine sediment.
Aquatic invertebrate sampling equipment	kick nets, Surber nets, or Hess samplers in coarse substrates, Peterson grabs, corers in fine sediment deposits, drift nets to evaluate food densities available to fish
Dominant functional feeding groups	Scrapers, Collecter-filterers, Predators
Invertebrate assemblage members	Amphipods - Gammarus lacustris, Hyallela azteca Diptera: Chironomidae,  Ephemeroptera: Baetis, Ephemerella inermis Plecoptera: Hesperoperla pacifica Turbellaria