Use of decision support systems to improve dam planning and dam ...

2.2 The impact of dams on river ecosystems
construction of a dam also results in phenomena (especially immediately after
Dams constitute human-made obstacles. They fragment rivers, disrupting the flow of water and other fluxes.
construction) that are unique and do not occur in natural lakes. However, the exact impact
Although in many ways reservoirs are similar to lakes, the construction of a dam also results in phenomena
of a dam depends on site specific conditions, the type of dam and the way it is operated.
(especially immediately after construction) that are unique and do not occur in natural lakes. However, the
exact impact of a dam depends on site specific conditions, the type of dam and the way it is operated.
Dams create a hierarchy of interconnected effects in which first-, second- and third-order
Dams
impacts
create
occur
a hierarchy
(Figure
of
2.2).
interconnected
Changes
effects
in physical
in which
driving
first-, secondvariables
and
(i.e.,
third-order
hydrology,
impacts
water
occur
(Figure
quality
2.2).
and
Changes
sediment)
in physical
are
driving
first-order
variables
impacts.
(i.e., hydrology,
As well
water
as changes
quality
to
and
the
sediment)
river system
are first-order
these
impacts. can also As well cause as changes changes to the within river system the terrestrial these can also system, cause changes for example, within other as aquatic a consequence and terrestrial of
ecosystems, reduced for flooding example, and as a sediment consequence transport of reduced to floodplains. flooding and Second-order sediment transport impacts to floodplains. are those
Second-order that arise impacts from are changes those that caused arise from by first-order changes caused impacts by first-order (i.e., typically impacts (i.e., changes typically to changes river
to river morphology morphology and and primary production). Third-order Third-order impacts impacts are those are that those arise from that changes arise caused from
by second-order changes caused impacts. by Usually, second-order the complexity impacts of interacting (i.e., typically processes changes increases from to flora first- to and third-order fauna).
impacts Usually, and they the are complexity increasingly difficult of interacting to predict. processes increases from first- to third-order
impacts and they are increasingly difficult to predict.
Figure 2.2. The impact of dams on river ecosystems (modified, from Petts 1984).
Figure 2.2. The impact of dams on river ecosystems (modified, from Petts 1984).
Alter the first letter of Macrophytes to lower case. Alter form to forms. Lower case S of
Substrate. Align quantity and regime with their foregoing words.
8
Terrestrial environment
Water
quality
Primary
production
Birds
Plankton
Aquatic Macrophytes
Algae
Mammals
Fish
Invertebrates
Water
quantity
Channel form
Substrate composition
Hydrology
Morphology
Barrier effects
16
Flow
regime
THIRD-ORDER
IMPACTS
Sediment
load
SECOND-ORDER
IMPACTS
FIRST-ORDER
IMPACTS