dams - impacts on a riparian environment

8/2/2019 Dams - Impacts on a Riparian Environment

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Dams

Impacts on a Riparian EnvironmentBy: Aaron Shaffer

Dept. of GeographyIndiana University of Pennsylvania


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2 Aaron ShafferDams Impacts on a Riparian Environment

Introduction

Since the beginning of time, the power of nature has had an impact on the existence of

every type of species on this planet. As for humans, we have been battling nature for survival for

much of our recorded history, most of the time losing. One force of nature that control has been

extensive fought for is water, or, more specifically, floods. In an effort to control this wrecker of

havoc on our settlements, humans developed a mostly effect form of flood control: the dam. In

blocking the water upstream to prevent flooding, have we really solved the problem of flooding

or have we only bought ourselves more time, destroying the natural balance of nature and

causing more damage for ourselves in the future? Should we not be trying to prevent this? This

topic has come up in one form or another and will be discussed in this research along with a brief

history and process of dam building.

Definition and Construction

The journey of 1000 miles begins with a single step, so therefore, let us start with the

basics. B y definition a dam is a large wall or barrier that obstructs or stops the flow of water,

forming a reservoi r or lake (Wikipedia). Simply put, a dam is constructed for the benefit of

mankind, either by preventing flooding or for storing water for consumption or irrigation for our

crops. Any sort of structure that holds back or diverts water is considered a dam, and have taken

many forms throughout the ages and across cultures, yet keep the same basic characterizes.

There are three main parts to a dam. The first is the most obvious when one thinks of a

dam, the outer wall. The wall is the bulk of the construct, which is, most times, placed

perpendicular to the flow of the river or stream and is what actively holds back water in the


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upper part, the reservoir. The water is released back into the main channel by the spillway or

weir. This varies from place to place and in some cases may be entirely non-existent, depending

on the purpose the dam serves.

And there are many purposes in which a dam may be constructed for. The most common

among these are to retain water, prevent flooding or to better control the flow of water but there

are still many other uses for constructing one. In modern times we have been able to harness the

power of water for reasons other than flood prevention and retaining water, namely, the practice

of creating commercial waterways in the form of canals and lock systems but also through

hydroelectric power plants, which utilize the power of the flow of the water and create electricity

via large turbines housed within the walls of the dam.

As it is said, Rome wasnt built in a day, is also the same with the process of building a

dam. Though it varies from place to place, the general procedure usually involves the same

steps: a need to put in a dam, a political approval process, a surveying process and then the actual

construction process. All of the above are affected by a huge number of factors including

geographical location, climate, population, economic condition, agricultural status, availability

and type of construction materials, available alternatives, and above all, the availability of the

areas water resources and their spatial and temporal land use distribution and overall national

development status.

Ancient History

The history of dam building goes back nearly 7,000 years to ancient Mesopotamia.

Throughout the ages, the advancement in science and technology, better knowledge of laws of

mechanics and new construction materials like cement and steel, gave way to the modern age of


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dam building. Starting in the 19 th and 20 th centuries, the full progressive force in building dams

came with the breakthroughs and realizations of the benefits of creating large storages to increase

in productivity in activities such as irrigated agriculture, which meant a guaranteed supply of

water for both domestic and industrial use. With the creation of the reservoir came other

activities as fishing, recreation, and eventually in the modern era, the generation of hydropower,

navigation and flood control all made dam building a very attractive proposal for economic

growth, jobs and development. However, on the other side of the benefits are the requirements,

implications, and consequences that come with building a dam and are, often times, overlooked.

As previously stated flooding and water in general are a powerful and often times

devastating force of nature. So in turn, a dam is an intervention of that power and must be able

to withstand its force in order to continually benefit mankind. However, because of this

intervention, there are many factors that come into play after the dam is constructed that must be

addressed and mitigated before the dam is installed. Issues that must be addressed and have been

historically ignored include the effects to the natural flow of a river, the submergence of land

upstream to create the reservoir, the displacement of native species, habitats, ecology,

biodiversity, people and capital investment, the decision to undertake such a grand endeavor lies

with the ruler of the territory or the local government.

Modern Marvelsand Complications

Many times, as with any legal process, the development becomes a political battle, as it

did with the construction of the Llyn Celyn Reservoir in Gwynedd, North Wales. Construction

of this dam to supply Liverpool with water involved the flooding of the village of Capel Celyn, a

highlight of Welsh culture and the Welsh language.


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In order to prevent incidents such as this, experts, advisers and planners play a key role in

formulating the dam proposals, and recommending these to the Head of State for a final decision.

A quote from the ICIDs Appropriate Decision Making Procedures for New Dams shows a

glimpse into the approval process in the US and also reflects the process in general: After a

decision to build the dam was made by the competent authority, the implementation was done by the

concerned agencies in accordance with the orders and there was little opposition from any quarters. It

was well-recognized that the project was taken up for the benefit of society at large . This statement is

an example of a legal verification of one such process that must occur in order to secure a stable

and healthy relationship not only with the public at large but also with the surrounding ecologicniche.

The decision-making process for newly proposed dams generally remains similar in most

post-industrial countries with government planning agencies playing the key role in the

procedural process. In recent years, considerable attention is paid to the environmental and

ecological considerations. Most countries have developed procedures, guidelines, standards and

restrictions in regards to these considerations. However, unavoidable long and short term

consequences make many of these procedures inevitably fall short of meeting the essential

natural environmental standards, making dams a questionable form of management practice.

As with any man-made obstruction to nature, dams pose a direct threat to the natural

environment in which they are placed. Dams incur a variety of environmental issues and

irreparable conditions that we are vaguely aware of. Only being realized in recent history, a dam

can quickly translate from a form of economic development to an environmental stressor. The

main purpose of dam in the first place is to block and restrict water flow which prevents


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sediments and nutrients from properly reaching the ecosystems downstream. If not managed

properly, the problems start small and build as time moves on. With no nutrients downstream,

the environment quickly deteriorates. Plant life withers away, herbivores must move to another

location to find food, which continues on up the food chain. Even properly managed dams still

loose riparian land area due to the flood prevention quality of the dam. For life further up the

stream banks, depending on the topography of the land, floods are a sustainable and dependable

source of nutrients which get deposited when a stream or river floods. Even controlled flooding

that only sometimes takes place, there are going to be an overall decrease in plant species.

A prime example of this is Chinas Three Gorges Dam. Constructed in 1919, this $180

Billion project has had huge impacts on both the environmental aspects as well as cultural

implications. A report published in 2007 in Time magazine stated that the project had the

potential to cause a huge [environmental] disaster ... if steps are not taken promptly. It goes on

to state that nearly 1.4 million residents have been uprooted by the nearly 400 mile long reservoir

that formed behind it, which also flooded several important archaeological sites in the area.

Worse still, it goes on, that some hydrologists believe that by trapping the silt and sediments in

the reservoir upstream, the dam could actually make downstream riverbanks more prone to

flooding. Three Gorges Dam is a perfect example of environmental impacts of dams and even if

properly managed the consequences can still be detrimental to the environment both upstream

and downstream.

One amazing thing about natural fresh waterways is their ability to automatically filter

the water as it flows downstream. Some plant species, specifically those in wetlands, are natural

water purifiers that automatically filter out harmful contaminants from the stream and allow

other minerals to settle naturally and in regulation. When we put in a dam, we destroy these


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natural water purification systems either by flooding them upstream or restricting water flow

downstream so that wetlands can no longer function.

Not only are dams harmful to life above the water, but also below it. One big

environmental issue with building dams is the detrimental effect on fish populations and habitats.

Migratory fish that depend on upstream/downstream movement are cut off from their natural

breeding and feeding zones by dams, which in turn may cause a loss of species and potentially

their extinction altogether. In the Eastern US alone, the construction of dams alone has been

identified as the primary reason for the decrease and extinction of migratory fish species

(Larinier, 49). A report on the the Xinanjiang Dam in China reported that the number of

migratory fish species decreased from 107 to 83 immediately following the construction of the

dam (Zhong 1996).

So far, we have discussed the history, construction, and impacts that dams have on an

environment. This brings us to a very important question in modern research: What happens if

you just remove the dam? Dam removal is a current initiative in the US by an organization

called American Rivers, which focuses on the removal of outdated and environmentally harmful

dams. Because dams are one of the only natural structures that have such a large impact on a

riparian environment, removing them also takes much research and surveying. The benefits of

this however, once approved, are numerous. Stream flow is once again restored downstream for

fish and wildlife populations to once again inhabit over time, as well as removing the build up

and flooding in the location of the reservoir. Fish species can once again find migratory routes

up the river and even start new routes. Over time and with the help of volunteers and with much

effort, removing a dam can once again restore a natural riparian habitat and the flow of

sediments to provide nutrients to the downstream corridor. Also, a natural water temperature is


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restored to the area and with the equaling out of the reservoir comes the removal of temperature

stratification which takes place in the deeper waters of the upstream area.

Along with environmental benefits, removing certain dams removes safety hazards for all

species, humans included, and give way to restoring the opportunity for recreation in the area,

which often times generate more local economic income than the dam itself did. In fact, there

are many more economical benefits of removing a dam that is outdated besides simply

recreational activities. As stated before, wetlands destroyed by the dam can once again restored

and are a much more cost-effective, natural form of flood control than dams are. Removing

dams may be more expensive in the short-term future due to demolition costs, but the long-term

benefits far outweigh the initial destruction of the dam. Wetlands, as opposed to dams, need no

maintenance and no repair, are self-sustaining and most times more efficient form of flood

control than dams are.

In the present, more energy efficient technology makes hydroelectric power and therefore

the construction of dams with hydroelectric power plants obsolete. The removal of the Edwards

Hydroelectric Dam on the Kennebec River in central Maine caused a decrease of 3 megawatts of

power output. In order to compensate for this loss of power, all that needed to be done was to

replace 75,000 regular light bulbs with energy efficient light bulbs in nearby Augusta, Maine,

which, according to the 2000 US Census, has 8,565 households which is a little less than 9 light

bulbs per household, not including businesses, apartment buildings and office tower complexes.

Another reputable source for the restoration of natural river environments is the

Hydropower Reform Coalition, which works in conjunction with American Rivers to repair and

restore the natural flow of the river downstream, benefiting fish and wildlife communities. The

Coalition includes the community to help in the removal process and engages with them to help


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support local dam removal movements. It also motivates politicians and civic leaders to set an

example for future and other removals and identifies state and local funds to aid communities in

making dam removals possible. So far, it has contributed to the removal of over 150 dams in the

US, as shown in Figures 1 an 2 below.

Fig 1. East Coast Dam Removals by American Rivers and the Hydropower Reform Coalition


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Fig 2. West Coast Dam Removals by American Rivers and the Hydropower Reform Coalition

Dams may have at one time been a beneficial production for many communities, but in

with our world in its current state, more renewable and sustainable ideologies must be accepted

to prevent further destruction to our ecosystems around the world. Unfortunately, not all of the

damage can be repaired, but choosing more natural, sustainable, and environmentally friendly

options, such as investing in wetland restoration instead of dam construction, will benefit us all

in the long run.


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Works Cited:

1. Thomas, Einion. Capel Celyn, Ten Years of Destruction: 1955-1965. 2007.

2. National Library of Wales. Tryweryn.

http://www.llgc.org.uk/ymgyrchu/Dwr/Tryweryn/index-e.htm

3. Yang, Lin. Chinas Three Gorges Dam Under Fire. Time World. 2007.

4. MWC News. China Dam to Displace Millions More. 2007.

5. Jurries, Dennis. Biofilters for Storm Water Discharge Pollution Removal. 2003.

6. Larinier, Michael. Environmental Issues, Dams, and Fish Migration. 2001.

7. American Rivers.org:

a. http://www.americanrivers.org/our-work/restoring-rivers/dam-removal-map/

b. http://www.americanrivers.org/our-work/restoring-rivers/dams/background/noaa-grants-program.html

c. http://www.americanrivers.org/our-work/restoring-rivers/dams/background/10-ways.html

d. http://www.americanrivers.org/our-work/restoring-rivers/dams/background/faqs.html

e. http://www.americanrivers.org/our-work/restoring-rivers/dams/projects/2010-dam-removals.html

f. http://www.americanrivers.org/our-work/restoring-rivers/dams/projects/2011-dam-removal-resource-guide.html

g. http://www.americanrivers.org/our-work/restoring-rivers/dams/

h. http://www.americanrivers.org/our-work/global-warming-and-rivers/

i. http://www.americanrivers.org/our-work/protecting-rivers/

j. http://www.americanrivers.org/our-work/restoring-rivers/floods-floodplains/
http://www.llgc.org.uk/ymgyrchu/Dwr/Tryweryn/index-e.htmhttp://www.llgc.org.uk/ymgyrchu/Dwr/Tryweryn/index-e.htmhttp://www.llgc.org.uk/ymgyrchu/Dwr/Tryweryn/index-e.htm

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