Dams are built for various purposes; the major function includes hydroelectric power generation, drinking water supply, irrigation, flood control, recreation etc. But the different incidents and studies done by several researchers proved that these large dams made for these purposes, also simultaneously pose substantial threats to the life, property and the environment throughout their lifecycle. The impacts may be different in different phases, namely construction, operation and decommissioning phase. There are about 845,000 dams around the world (Jacquot, 2009), the cumulative impact of all these dams could be enormous. So, it is essential to minimise the impacts due to dam construction on lives, property and environment. Identifying possible impacts, calculating risk and minimising the risk through the adoption of various techniques could help to lower the overall impacts.
Major hazards associated with Dams throughout their lifecycle (Reservoir):
Construction Phase:
Construction of large infrastructure like dams demands massive amount of construction material, excavation process and vehicles, which directly impacts on the environment and society. Most of the equipments and vehicle engage on such activities use fossil fuel as the principal source of energy and contribute to the green house gas emission. The estimated emission from Glen Canyon dam during its construction phase was calculated as 800,000 metric tons of CO2 equivalent (Pacca, 2002). The risk of accidents due to the vehicles, construction activity and excavation process to the worker is probable. The construction site could be of special interest for some animal or plant, so this activity may lead to the disappearance such plant/animal from that area for ever.
Operation Phase:
The operation of dams also poses threat to the environment and people. The threat of dam failure during the operation phase due to various reasons may cause huge loss of life and property. There is always threat of drawing of people on the dam. The emission during this phase from the decay of biomass in the reservoir is obvious; the emission from the Glen Canyon dam during its operation phase was estimated to be 3,500,000 metric ton of CO2 equivalent (Pacca, 2002). The failure of dam is the most destructive event of the entire lifecycle of dam. The details on dam failure are discussed separately below.
Decommissioning Phase:
This is the last stage of the life cycle of dam, this stage pose threat of sweeping the downstream areas (settlements, infrastructure, etc) and the lives. The emission from this stage is found as largest in comparison with construction and operation. The emission from the decommissioning of the Glen Canyon dam was calculated as 33,000,000 metric tons of CO2 equivalent (Pacca,2002), which was more than nine times the emission from the entire operation phase. Though the decommissioning work is done in controlled manner, the loss of property would not be as the dam failure.
Environmental and Social consequences throughout a dam’s life:
Construction Phase:
Resettlement of people: Construction of Dam requires huge area of land, which is often acquired by displacing people from that place. People are often forced to leave their inherited land giving them psychological stress and the resettlement to the new location often alters the existing environment there. In China Three Gorges Dam have already displaced a million people and still another 80000 are to be moved till its final stage, 1200 villages and 2 major towns have had to be abandoned and rebuilt (McGivering, 2006).
Archaeological sites: In some cases even the archaeological sites also get destroyed due to dam construction. More than 100 archaeological sites, some dating back over 12000 years is to be submerged due to the three gorge dam (Gleick, 2009).
Transportation, excavation and construction: The movement of vehicles during the construction of dam contributes to emission to some extent and equally disturb the ecology there. The excavation and construction process both impact the ecology locally. Air pollution due to the dust can be expected.
Operation Phase:
Siltation: Rivers carry sediment loads, the amount vary according to the characteristics of the catchment area and the velocity of the running water. The construction of dam reduces the velocity of the river thus helping sediment to settle down within the reservoir. If the sediment deficit exit due to this in river, the channel can be expected to evacuate sediment from its bed and banks in the downstream effecting the environment there (Grant,2003).
Methane Generation: Hydro power was considered to be the renewable that produce no greenhouse gases. According to Boyle, G (2009), a report by the world commission on dams (WCD, 2000, Anon, 2001), the decaying of vegetable matter in an anaerobic condition produces methane (CH4), when the land is flooded with hydro project.
Fish migration: Fish are affected directly by the obstruction like dam on its course. The most commonly affected species like Salmon, which needs to go upstream for spawning, can be obstructed from their spawning place. Inundation of the spawning grounds within the reservoir, periodic inundation and drying out of spawning ground and refuge area downstream of the dam further hampers the fish’s activity. (Harvath, and Municio,1998).
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Fertility of the downstream plains: The downstream part of dam loose the nutrient containing soil, which used to receive during flooding. After the building of the Aswan dam, in 1960’s, the land downstream no longer receives the soil and nutrients previously carried by the annual Nile flood. The agricultural system has been destroyed in the downstream and to be replaced and is replaced by irrigation and chemical fertilizer (Boyle, 2004).
Local climate change: Increased precipitation has been observed after the construction of dam, the physical process by which large scale surface evaporation triggers in the precipitation recycling in such area (Hossain, et al, 2009). Changes in the air moisture percentage, air temperature, air movement in big scale can be caused by big scale dam (Tahmiscioglu, et al,….).
Impact on biodiversity: In some cases building of dams disturb the habitat of critically endangered species too, the winter shelter of Siberien Crane and the ‘Baiji’ Yangtze river dolphin, are found to be affected by the three gorges dam (http://en.wikipedia.org/wiki/Three_Gorges_Dam).
Induced earthquakes: large reservoirs can cause seismic events as they fill, as the pressure on local faults increases (ICE 1981). The seismic activity of magnitude 5.7 was recorded in Lake Oroville in Butte county of California in June 1982(Allen, 1982).
Agricultural/ loss of forests: In many cases, the construction of dam covers the productive agricultural land which used to be the means of sustenance for the local people and in many cases clear some part of forest destroying natural ecosystem. About 1400 hector of agricultural land is to be submerged because of the three gorge dam (Gleick, 2009).
Spread of disease (increase in disease carrying vectors, e.g. mosquito): Study carried out by Yewhalaw, et al (2005), found that the impoundment can act as breeding ground for vectors like mosquito, and found that the children living near to dam are at greater risk of plasmodium infection than the children living away.
Decommissioning Phase:
Decommissioning: Even though, decommissioning of dams help to restore the reverine ecosystem to its natural condition, some short term negative effect such as sediment mobilisation, contaminated material and threat of super saturation can be seen (Bednarek, 2001).
Dam Failure:
One of the most obviously harmful effect of large dam is seen, when it falls. The underlying causes may be different in each case. Some of the major causes are (ICOLD, 1973):
Overtopping
Foundation defects
Piping and seepage
Conduits and valves
Seismic event damage
Failure of dam due to internal water pressure
Failure of dam due to prolonged period of rainfall and flooding
Causes of Dam Failure that occurred between 1075- 2001(NPDP, 2007)
(Adopted from historic records of Dam Performance, 2007)
On the basis of the above graph it can be said that, flood or overtopping of the dam wall stand far ahead from other causes of dam failure. Seepage and piping is on second position and rest of all are responsible for very less number of dam failures, this graph proves that the overtopping of dam is the major causes of dam failures.
Cost of Dam Break: The cost of dam break consists of two components; reconstruction cost of dam and economic loss due to destruction and inundation downstream (Kuo, et al, 2008).
Cost and Benefit from Dam: Dam construction is an expensive work and demands huge sum of money, but it provides extremely necessary things for running the society and development like energy and water for drinking and irrigation purpose. On the other hand it has some impacts on society and environment, some of which needs lots of money and time for restoration while others are irreparable. So construction of dam has its own pros and cons.
Ways to minimise the occurrence of dam failure:
Dam failure is the most destructive incident in the entire life cycle of dam, which may cause huge loss of life and property. So it is essential to ensure the safety of dam in order to protect the life and property. Some of the important steps essential for the reduction of dam failure and its impacts are as follows (MDE, 1996):
Strict legislation should be promulgated by government for the construction of dam/ Reservoir.
Routine deformation monitoring of seepage from drains in and around larger dams is necessary and if found faulty, corrective measure should be taken. In case of wall fracture, rock grouting (pressure pumping of cement slurry) can be done to reduce the risk of dam failure. Regular monitoring and maintenance could help a lot to prevent dam failure.
Early warning system should be incorporated in the reservoir system to protect people and property downstream, in case of dam failure.
Dam construction should not be allowed in the area of high seismic activity.
Most of the nations make safety programme for the protection of dam. In USA most of the ‘states’ are responsible for the safety of dams within their boundary and to ensure the safety they regularly follow the following procedure (Lane, 2008);
Evaluate the safety of existing dam.
Review plans and specification for safety and regulatory programme.
Carry out periodic inspection on construction on new and existing dams.
Review and approval of emergency action plan.
Some measures to reduce other impacts on and due to dams:
Management of catchment of river can help to reduce sedimentation on dam, which may include plantation on the catchment area, adoption of landside and erosion control measures for the upstream area of dam. The periodic cleaning of dams can help to reduce the load of sediments within a dam and help to reclaim the capacity to its original form. Fish ladder can help to restore fish migration to some extent. (source)
The calculation of probable maximum precipitation (PMP) and estimation of probable maximum flood (PMF) and the probability of average return period for that river, could help to design the dam properly (CSCD,1985), which could prevent dam from failure.
Monitoring should be carried out to control the breeding of mosquitoes in dam, if found, mosquito larvae must be controlled with the approved mosquito larvicide, so that the other aquatic organism will have minimal impacts from larvicide (DHF,2006).
Rich picture of Dam and associated Impacts
A Rich Picture illustrating impacts of dam on various aspects of environment and society
Risk of Dam Failure with age:
Percentage of different age groups of dam failures in Russia in comparison with the failures of world dams.
(Adopted from Management of Impounded Rivers, Wang and Melching, 2007).
Though age is one of the important factor for the dam failure as the walls and other infrastructures erodes or weakens with age, but it is not only the factor that causes dam failure; faulty structures, extreme weather events, sabotage, seismic activities etc also trigger to dam failure. The above graph showed that the highest number of dam failure was in the age group 0-10, which then gradually decreases as the age group increases. The defective structure can lead to dam failure even at its early age while the well constructed and well maintained dam can serve over hundred years. On the basis of above graph it can be said that aging in not the primary factor for dam failure and proper maintenance can lengthen the life span of dam despite of age, and does not show clear correlation with dam failure. One probable reason of less number of dam failures of the aged dam could be the proper maintenance and decommissioning before the dam failure occurs.
Risk Assessment of dam failure:
Risk assessment was calculated on the basis of data from Annex-3.
High severity condition
Total Occurrence= 11
Average time taken to repeat the events for the class IA (with more than 300 deaths) =11.1 year
Average Death calculated=1111.1
Risk=Frequency (event/ unit time) -Magnitude (Deaths)=1/11.1-1111.1=0.09-1111.1=99.99
Therefore, Risk=99.99 per 11.1 year
Risk calculation for overall dam failure
Total occurrence of dam failure=46
Average gap between successive events=0.39 year
Average death per event=357.91
Risk= Frequency (event/ unit time) -Magnitude (Deaths)
Therefore, Risk= 1/0.39-357.91=2.6-357.91=930.5 person per 0.39 year
Conclusion:
References:
Allen, C,R, 1982, Reservoir Induced Earthquakes and Engineering Policy, California Geology, 35, 11
Bednarek, A,T, 2001,Undamming Rivers: A Review of the Ecological Impacts of Dam Removal, Environmental Management, 27,803-814.
Boyle, G, 2004, Renewable Energy: Power for a Sustainable Future, Oxford University, Oxford
CSCD,1985, Safety of Dams: Flood and Earthquake Criteria, National Academy Press, Washington D.C.
DHF, 2006,Guidelines for Preventing Mosquito Breeding Sites Associated with Aquaculture Development in NT,Department of Health and Families, Darwin
Gleick, P.H., 2009, Three Gorges Dam Project, Yangtze River, China, Water Brief, 3, 139-150.
Grant, E, G, et al, 2003, A Geological Framework For Interpreting Downstream Effects Of dams On Rivers, Water Science and Application 7, 209-225
Harvath, E, and Municio, M. A. T.,1998, 2nd International Symposium in Civil Engineering, Budapest
Hossain, F, et al, 2009, Local Climate Change, EOS, 90,453-468
http://en.wikipedia.org/wiki/Three_Gorges_Dam, assessed on 4 March, 2010.
http://www.internationalrivers.org/files/srdamsafety.pdf, assessed on 20 May, 2010
http://npdp.stanford.edu/npdphome/Historic%20Performance%20of%20Dams.pdf, assessed on 20 May ,2010.
http://www.damsafety.org/, assessed on 20 March, 2010
International Committee on Large Dams (ICOLD, 1973),Lessons from Dam Incidents,Reduced Edition, Paris
Jacqot,J,2009, Numbers Dams; From Hoover to Three Gorges to the crumbling ones, Environmental Policy, http://discovermagazine.com/2009/mar/08-dams-hoover-three-gorges-crumbling-ones, assessed on 17 May 2010.
Kuo,J,T, et al, 2008,Dam Over Topping Risk Assessment Considering Inspection Programme, Stoch Environ Res Risk Assess, 22, 303-313
Lane,N, 2008,Aging Infracture: Dam Safety, Congressional Research Service
McGivering, J, 2006, Three Gorges Dam’s Social Impact, BBC , http://news.bbc.co.uk/1/low/world/asia-pacific/5000198.stm, assessed on 3 March 2010.
MDE, 1996, Maryland Dam Safety Manual, Association of State Dam Safety Officials
Pacca,S, 2007, Impacts from Decommissioning of Hydroelectric Dams: A life Cycle Prospective, Climate Change, 84, 281-294
Tahmiscioglu, M, S, et al,.. Positive and Negative Impacts of Dam on the Environment, International Congress on River Basin Management, 760-769
Wang,Z,Y, and Melching, S, 2007, Management of Impounded Rivers
Yewhalaw, D, et al, 2005, Malaria and Water Resource development: The Case of Gilgel-Gibe Hydroelectric Dam in Ethopia, Malar. J, 8, 21
Annex-1 (Part-A)
PLAGARISM DECLARATION
I declare that the work I am submitting for assessment contains no section copied in whole or in part from any other sources unless it is explicitly identified by means of quotation marks. I declare that I have also acknowledged such quotation by providing detailed references in an approved format. I understand that either or both unidentified and unreferenced copying constitutes plagiarism, which is one of a number of very serious offences under the university’s code of practice on the Use of Unfair Means.
Student No- 200910979
LIFE CYCLE ANALYSIS OF A DAM
CONTENTS PAGE NO.
INTRODUCTION: 3
Major hazards associated with Dam: 3
Major environmental issues associated with dam 3-4
Catastrophes (Dam failure):
Siltation
Methane generation
Fish migration
Resettlement of people
Fertility of the downstream plains
Local climate change
Impact on biodiversity
Induced earthquakes
Agricultural/ loss of forests
Spread of disease
Archaeological sites
Decommissioning
Key questions for part B 5
Draft Plan 5
References 6
Word Count- 1076
Word Limit- 1000
INTRODUCTION:
Dams are built for various purposes; the major function includes hydroelectric power generation, drinking water supply, irrigation, flood control, recreation etc. But the different incidents and studies done by several researchers proved that these large dams made for these purposes, also simultaneously pose substantial threats to the life, property and the environment throughout their lifecycle. The impacts may be different in different phases, namely construction, operation and decommissioning phase. Yes, but what is th eproblem situation or concern?
Major hazards associated with Dam:
Dam failure: one of the most obviously harmful effect of large dam is seen, when it falls. The underlying causes may be different in each case. Some of the major causes are:
Seismic event damage
Failure of dam due to internal water pressure.
Failure of dam due to prolonged period of rainfall and flooding.
Threat to human life due to drowning in dam.
Major environmental issues associated with dam:
Catastrophes (Dam failure): Dam failure often results huge loss of life, property and environment. During 20th century some 200 dam failures caused more than ten thousand people outside China and in the year 1975 only about quarter of million people were perished in the series of hydroelectric dam failure in China (Boyle, G, 2004).
Siltation: Rivers carry sediment loads, the amount vary according to the characteristics of the catchment area and the velocity of the running water. The construction of dam reduces the velocity of the river thus helping sediment to settle down within the reservoir. If the sediment deficit exit due to this in river, the channel can be expected to evacuate sediment from its bed and banks in the downstream effecting the environment there (Grant,2003).
Methane generation: Hydro power was considered to be the renewable that produce no greenhouse gases. According to Boyle, G (2009), a report by the world commission on dams (WCD, 2000, Anon, 2001), the decaying of vegetable matter in an anaerobic condition produces methane (CH4), when the land is flooded with hydro project.
Fish migration: Fish are affected directly by the obstruction like dam on its course. The most commonly affected species like Salmon, which needs to go upstream for spawning, can be obstructed from their spawning place. Inundation of the spawning grounds within the reservoir, periodic inundation and drying out of spawning ground and refuge area downstream of the dam further hampers the fish’s activity. (Harvath, E, and Municio, M. A. T.,1998).
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Resettlement of people: Construction of Dam requires huge area of land, which is often acquired by displacing people from that place. People are often forced to leave their inherited land giving them psychological stress and the resettlement to the new location often alters the existing environment there. In China Three Gorges Dam have already displaced a million people and still another 80000 are to be moved till its final stage, 1200 villages and 2 major towns have had to be abandoned and rebuilt (McGivering, 2006).
Fertility of the downstream plains: The downstream part of dam loose the nutrient containing soil, which used to receive during flooding. After the building of the Aswan dam, in 1960’s, the land downstream no longer receives the soil and nutrients previously carried by the annual Nile flood. The agricultural system has been destroyed in the downstream and to be replaced and is replaced by irrigation and chemical fertilizer(Boyle, G, 2004).
Local climate change: Increased precipitation has been observed after the construction of dam, the physical process by which large scale surface evaporation triggers in the precipitation recycling in such area (Hossain, F, et al, 2009). Changes in the air moisture percentage, air temperature, air movement in big scale can be caused by big scale dam (Tahmiscioglu, M, S, et al,….).
Impact on biodiversity: In some cases building of dams disturb the habitat of critically endangered species too, the winter shelter of Siberien Crane and the ‘Baiji’ Yangtze river dolphin, are found to be affected by the three gorges dam (http://en.wikipedia.org/wiki/Three_Gorges_Dam).
Induced earthquakes: large reservoirs can cause seismic events as they fill, as the pressure on local faults increases (ICE 1981). The seismic activity of magnitude 5.7 was recorded in Lake Oroville in Butte county of California in June 1982(Allen, C,R, 1982)
Agricultural/ loss of forests: In many cases, the construction of dam covers the productive agricultural land which used to be the means of sustenance for the local people and in many cases clear some part of forest destroying natural ecosystem. About 1400 hector of agricultural land will be submerged because of the three gorge dam (Gleick, P.H., 2009).
Spread of disease (increase in disease carrying vectors, e.g. mosquito): Study carried out by Yewhalaw, D, et al (2005), found that the impoundment can act as breeding ground for vectors like mosquito, and found that the children living near to dam are at greater risk of plasmodium infection than the children living away.
Archaeological sites: In some cases even the archaeological sites also get destroyed due to dam construction. More than 100 archaeological sites, some dating back over 12000 years will be submerged due to the three gorge dam (Gleick, P.H., 2009).
Decommissioning: Even though, decommissioning of dams help to restore the reverine ecosystem to its natural condition, some short term negative effect such as sediment mobilisation, contaminated material and threat of super saturation can be seen (Bednarek, A,T, 2001).
Key questions for part B:
Answer to the following questions will be searched in the second part of this case study:
What are the major hazards associated with dam and how the risk can be minimised?
What are the approaches practised to minimise the impact on dam on environment and human?
How the dam induced impact like sedimentation, obstruction on the fish migration route and increase in diseases carrier vector can be regulated?
How the regulating body ensure the safety of dam?
How the factors like politics and economy affect in the construction of dam?
Draft Plan:
Introduction
Major hazards associated with Dam (Reservoir)
Causes of Dam failure
The possible impacts of such hazards
Measures to minimise the impacts
Environmental Issues associated with Dam
Impact on agriculture and forest
Impact on fish migration
Impact on biodiversity
Measures practised to minimise the impact
Socio economic impact of Dam
Abandonment and resettlement of displaced people
Damages to ancient heritage (archaeological structure)
Ways to minimise the damage to ancient heritage
Cost Benefit Analysis of Dam
Conclusion
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