7843 - Laserfiche WebLink

Home Browse Search

Flow regime Table 4.2. Primary ways that human-induced alterations impact river ecosystem biological integrity (modified from Karr [1991]). Biotic interaction Habitat structure Water quality Food source Discharge Water depth Water velocity Floods Droughts Dynamic inundation of aquatic-terrestrial transition zone (ATTZ) during peaking Sediment transport Depletion-reduced minimum flows and velocities Storage-reduced innundation of AZZT, reduced energy input Reduced reproductive success of floodplain rearing fish species Peaking hydro-increased extremes (magnitude and frequency of high and low flows) Reduced diversity of depth/velocity combinations Reduced feeding stations Channel geometry Floodplain connection Substrate material Percentage offines Meso-type diversity (pools, runs, chutes, backwaters, rimes, woody materials) Bank stability Cover objects Riparian vegetation Decreased stability of banks Increased siltation over substrated material Removal of trees from riparian zone Reduced cover-loss of undercut banks and woody debris Isolation of floodplain from channel Channelization-reduced sinuosity more uniform water depths Increased erosion from watershed (timbering, grazing, urban sprawl) Important Variables Temperature Particulate organic material Dissolved oxygen Terrestrial insects Turbidity Seasonal pattern of energy Nutrients input from floodplain and Dissolved chemicals watershed Heavy metals and toxics pH Disruptions Increased or decreased Isolation of floodplain turbidity and removal of riparian Altered temperature vegetation leads to regimes decreases in organic Altered diurnal dissolved materials (coarse and fine oxygen cycle particles Altered salinity Increased algal production Increased nutrients, toxics due to input of nitrogen or suspended solids and phosphorus Altered decomposition rates Competition for food and space Predation Disease Parasitism Shift in species composition and abundance-fishes and invertebrates Introduction of exotic species Disruption of seasonal rhythms Alterations in primary and secondary production- trophic structure Shifts in habitat guilds- (increased omnivores and decreased piscivores) Increased hybridization among fishes Decrease in obligate riverine fish species Increasing numbers of candi- date species for listing as threatened or endangered - ~ lzJ ..... Z ~ ~ ~ o :E! ..... ~ [;j ~ ~ is: lzJ if o t'" t::J o ~ ~ 01