Newsletter and Technical Publications
<Lakes and Reservoirs - Similarities, Differences and Importance>
The overall conclusion of the assessment report was that the Aswan High Dam
has had an overall positive effect, although it contributed to some significant
environmental problems as well. The results of further detailed analyses like
this one will undoubtedly provide information and guidance to those considering
the construction of large dam projects in future years, particularly in
developing countries.
|
Table 2. Positive and negative effects of
large reservoir construction* |
|
| Positive Benefits |
Negative Effects |
|
- Production of energy (hydropower);
- Increased low-energy water quality improvement;
- Retention of water resources in the drainage basin;
- Creation of drinking water and water supply resources;
- Creation of representative biological diversity reserves;
- Increased welfare for local population;
- Enhanced recreational possibilities (Photo 27);
- Increased protection of downstream river from flooding events;
- Increased fishery possibilities;
- Storage of water for use during low-flow periods;
- Enhancement of navigation possibilities;
- Increased potential for sustained agricultural irrigation
|
|
|
|
- Displacement of local populations following inundation of reservoir
water basin;
- Excessive human immigration into reservoir region, with associated
social, economic and health problems;
- Deterioration of conditions for original population;
- Increased health problems from increasing spread of waterborne
disease and vectors;
- Loss of edible native river fish species;
- Loss of agricultural and timber lands;
- Loss of wetlands and land/water ecotones;
- Loss of natural floodplains and wildlife habitats;
- Loss of biodiversity, and displaced wildlife populations;
- Need for compensation for loss of agricultural lands, fishery
grounds and housing
- Degradation of local water quality (Photo 31);
- Decreased river flow rates below reservoir, and increased flow
variability;
- Decreased downstream temperatures, transport of silt and nutrients;
- Decreased concentrations of dissolved oxygen and increased
concentrations of hydrogen sulfide and carbon dioxide in reservoir
bottom water layer and dam discharges;
- Barrier to upstream fish migration;
- Loss of valuable historic or cultural resources (e.g., burial
grounds, relic sites, temples);
- Decreased aesthetic values
- Increased seismic activity
|
*Not all impacts occur in individual reservoir cases. |
|
Protection of Lakes and Reservoirs
As noted, lakes and reservoirs are complex aquatic ecosystems, as well as
important sources of water for human use and ecosystem maintenance. Many people
assume that the management and protection of lakes and reservoirs is primarily a
function of the local, state or federal government. It is certainly true that
most major water supply development, flood and water pollution control efforts
are usually carried out or directed by governmental bodies in one way or
another, but much can also be done at the level of the individual. Collectively,
individual citizen input can contribute significantly to protecting and
conserving lakes and reservoirs and their living aquatic resources. To
effectively protect a lake or reservoir, for example, it is desirable to gather
as much information as possible about it. This can help to define problems and
consider solutions. Because of public and political pressures, however,
decisions about environmental protection must sometimes be made in a relatively
short time, regardless of the state of knowledge on the problem. Ironically, in
some cases the problem is not too little information, but rather how to make
sense of an array of persuasive fact and/or opinion on both sides of an issue.
In such cases, solutions are sometimes sought with little real knowledge of
facts and even less knowledge about consequences.
The public can play a major role in such situations and it can be very
beneficial to seek the public’s view, in the form of public hearings or other
relevant fora. An example is the creation of a citizen’s advisory committee,
including inhabitants that live in the lake or reservoir drainage basin. These
committees can provide valuable insights and information about past conditions
of a lake or reservoir, particularly in the absence of written records. In such
cases, narrative descriptions of prior conditions, remembered by ‘elders’
can be used as an initial reference point for identifying current problems and
possible solutions. Some basin inhabitants also may have specific expertise they
can bring to bear, e.g. engineers, limnologists and chemists. The participation
of non-technical individuals is equally important in protecting lakes and
reservoirs, e.g. farmers, urban planners, lawyers, economists and communication
specialists. Knowledge gained in this manner can be disseminated among the
general basin population, and so prepare people for more informed future
judgments and actions. The nature of such materials can vary with the intended
audience, and its dispersal can include the press, television and radio, and ‘popular’
publications. Such efforts facilitate the development of a proprietary interest
on the part of the drainage basin inhabitants regarding the nature of lake or
reservoir problems, and make them more sympathetic to bearing the costs of
solutions.
The views of individuals and groups can inform decision-makers of the public
will. Drainage basin-scale environmental education and training activities are
also important activities in this respect. Citizens can form partnerships with
relevant authorities to identify lake and reservoir problems and map-out
solutions. Citizens can be especially effective in advocacy efforts, and in
lobbying for specific issues directed to lake and reservoir protection. Maximum
use should be made of the media, particularly in helping identify and highlight
lake and reservoir problems and the consequences of ignoring them. Indeed, the
possibilities for public involvement in protecting and conserving lakes and
reservoirs are limited only by the imagination and ambition of facilitators and
participants (Photos 28, 29 and 30).

Many simple protection and conservation actions within a lake or reservoir
drainage basin can be directly undertaken by individuals; reducing or
eliminating polluting wastes at the source, for example, can be done within
households, including using smaller amounts and/or substitutes for polluting
materials. Considerable water savings can be made by reduced and/or more
efficient water usage in households. Indeed, virtually any activity on the level
of the individual household that reduces the usage of water and the generation
of water polluting wastes will benefit lakes and reservoirs in the same manner
as their application at the drainage basin level.
Lake and reservoir protection measures often may consider ‘high tech’
solutions to pollution problems; such options as constructing treatment plants
to treat polluted water prior to its discharge to lakes and reservoirs, as well
as recycling or reusing wastewaters. However, ‘low-tech’ can often be
effectively applied by individuals. Such options typically include changing
ingrained behaviour patterns, ranging from convincing farmers to change their
agricultural fertilizer application practices to educating people about the
dangers of spreading their wastes indiscriminately on the land surface where
they can be washed away in storm runoff. As another example, a farmer far from a
lake or reservoir may not appreciate his/her role in causing problems.
Accordingly, ‘low-tech’ approaches typically must include some effort to
increase public awareness and education, to provide information to individuals
on how they can contribute to solving lake and reservoir problems.
Even after efforts to resolve
a lake or reservoir water quantity or quality problem, one’s efforts may not necessarily
be completed: any conclusion that further actions are not required can be false.
In fact, post-project monitoring always should be undertaken to evaluate the effectiveness
of lake and reservoir protection measures or programs.
Monitoring efforts also provide a basis for determining the extent of
improvements achieved, and for determining whether or not the lake or reservoir
protection goals are being achieved, as well as for making needed corrections to
an ongoing program. The longer a lake or reservoir takes to respond to
protection measures, the longer the period of time needed for post-program
monitoring efforts.
|