Instream structures
Key threatening process
Installation and operation of instream structures and other mechanisms that alter natural flow regimes of rivers and streams.
Description
Instream structures that modify natural flow include dams, weirs, canals, navigation locks, floodgates, culverts, flow regulators, levee banks, erosion control structures and causeways.
Mechanisms that alter natural flow regimes include the operation of the above structures as well as water extraction, pumping and diversion, and sand and gravel extraction.
Alteration to natural flow regimes can occur by reducing or increasing flows; altering the seasonality of flows; changing the frequency, duration, magnitude, timing, predictability and variability of flow events; altering surface and subsurface water levels; changing the rate of rise or fall of water levels; and by altering water temperatures.
