An introduction to the effects of dams
Nonmigratory, eurytopic species dominate the lacustrine zone of reservoirs because they usually have less complex requirements with regard to life-cycle dynamics. Reservoir flushing is an important mitigation measure for sediment remobilization and, thus, the restoration of natural sediment dynamics, including the formation of type-specific habitats.
Problems caused by dams
The intensity of impacts depends mainly on the concentration and duration of exposure, but also the size and texture of particles, water temperature, and chemical and physical conditions. BOX 1. Dams also alter environmental conditions, including changing water temperatures, oxygen concentrations, and nutrient loads that can substantially alter the ecology of river systems, as can be seen in the case of the Colorado River below Glen Canyon Dam see below. Changes to Earth's Rotation Nasa geophysicist Dr. Post-disaster recovery planning can minimize hazards caused by the disaster, or minimize hazards that may emerge in the turbulent period following a disaster. Because resilience is dynamic, it requires continuing managerial and social change among the individuals, networks, and institutions that make up a community. Impoundments redistribute river discharge in space and time, affecting several hydrological attributes, e. Effective collaboration extends beyond the provision of data by dam and levee owners on the degree of risk faced by communities and may include, for example, dam and levee owners acting as champions of community hazard mitigation and convening meetings of community members and stakeholders to discuss the serious nature of risk and the mitigation actions that are appropriate. This transformed dam design from an art based on empirical methodology to a profession based on a rigorously applied scientific theoretical framework. Spillflow at high dams may cause oversaturation of oxygen creating the so-called gas bubble disease in fish.
Impoundments redistribute river discharge in space and time, affecting several hydrological attributes, e. To make the switch from the lower to upper sluice, the outlet of Sand Lake was blocked off. The committee recognizes two facets of community. Adaptation refers to adjustments to a new or changing environment that take advantage of beneficial opportunities or moderates negative effects NRC, a.
Due to raised water tables and sedimentation in the impoundments, the drastic loss of originally typical instream structures gravel bars and islands strongly affects reproduction and young-of-the-year habitats of the rheophilic fish community.
Species Extinction As fisheries become an increasingly important source of food supply, more attention is being paid to the harmful effects of dams on many fish and marine mammel populations.
Bypass structures, whether they are tunnels, constructed canals, or existing river channels, can be used to pass high sediment-bearing water and bedload around an impoundment, thus decreasing the trapping of sediment.
Positive and negative impacts of dams on the environment
In all three zones of the reservoir, biodiversity is highest in the littoral environment as a result of the greater availability and heterogeneity of feeding resources, shelter, and habitats Agostinho et al. If coldwater streams are dammed, the warmer water in reservoirs might favor species adapter to warmer temperatures, resulting in a so-called potamalization effect, i. Leitbild-specific measures for the rehabilitation of the heavily modified Austrian Danube River. Nevertheless, reservoir flushing is also associated with immediate negative effects on physicochemical conditions, e. Flushing is a sustainable operation and a long-term equilibrium storage capacity can be reached. When the capacity mean annual flow ratio is less than 0. Physical and Social Infrastructure and Resilience Dams and levees serve different functions in the control of surface water, but regardless of initial intent in design, they are components of surface-water systems. Reservoir flushing can cause TSS concentrations much higher than the natural background concentration and can result, depending on concentration level and duration, in stress or complete elimination of the fish stock. Infrastructure decisions made for one part of a river system are likely to affect other parts of the system. The new lentic ecosystem resembles lake-type systems, but, depending on type and dam operation, reservoirs are disturbed by artificial water level fluctuations, drawdowns, and floods. Click for answer There are also impacts of ponded waters on human health, particularly in tropical regions where diseases and parasites are harbored by the biota in warm, slowly circulated waters. Also, further downstream, lack of sediment may cause habitat degradation due to erosion of river deltas or coastal shores. Walker and Salt , p.
based on 82 review