Environmental Impacts of Dams - Research Paper Example

ENVIRONMENTAL IMPACTS OF DAMS Introduction Dams are an integral part of human civilization and its progress. Long before knowledge about hydrology and civil engineering were introduced and became instrumental to the construction and operation of large dams, the socio-economic benefits of having a water reservoir for drinking water and irrigation supply, flood control, hydropower, recreation, and navigation have been recognized and exploited (Tahmiscioglu et al., 2007). With the advancement of industries and technologies as well as knowledge relevant to dam building, the growth of dam development was inevitable and rapid, especially from the 1950’s and onwards; presently, dams obstruct and alter about 60% of major river basins throughout the world (Sadler et al., 2000). Large dams have become controversial over these past several years, however, particularly with regards the socio-economical and environmental risks that have been associated with major impoundments and massive-scale reservoir. Some studies have revealed that economic impacts downstream of the dam are offset by the disruptions it will invariably cause to the economic activities of upstream dependents (Duflo & Pande, 2007). The displacement of affected communities has been hotly contested by human rights group. Environmental advocates, on the other hand decry the adverse effects on the ecosystem where dams alter and fragment the landscape and modify hydrological regimes with various repercussions (Brown et al, 2009; Burke et al, 2009; Kondolf, 1997; Gordon & Meentemeyer, 2006). While social concerns are grave issues, the discussion for this paper will maintain sole focus on the environmental impacts of dams. Despite its checkered history, dams remain just as important to human society as it was before the associated risks came to light. In the context of social development, dams are playing an important role in light of the fact that a growing population means a growing water demand and in some ways that demand is buffered by water reservoirs (Tahmiscioglu, et al., 2007). As well as that, water scarcity and security is fast becoming a national, even regional, issue. Problem Statement Where dams are concerned, there is a demand for the economic, energy, social, and environmental benefits afforded by dams which is simultaneous with demands for human rights protection, ecological preservation, and even a review of its perceived economic development contribution. Both sets of demands may seem mutually exclusive but they must both be met (Sadler et al, 2000). Nevertheless, economic gains and financial returns must not be the only consideration; traditional development paradigms are being replaced by the shared goals of sustainable development (Sachs, 2008). Dams, being the instrument of not only economic advancement but also of social persecution and environmental degradation must rise up to this challenge in order to deliver sustainable progress. Studies on environmental repercussions of large dams are not new and there are now so many of them to leave doubt as to the veracity of the idea that the magnitude of the impacts is great and further multiplied by compounding effects. What is relatively new, however, is how these studies can end the debate between the economic importance of dams and the urgent need to protect environmental integrity (Burke et al, 2009; Brown et al., 2009). We are at an era where we cannot ignore the imminence of ecological degradation that our oftentimes pollutive economic activities cause; on the other hand, we cannot totally dispense with such economic pursuits. Environmental protection must not be seen as a hindrance to economic development but its consideration a guiding framework. Objectives This paper aims to evaluate the positive and negative environmental impacts of dams from selected literature and what the implications of these impacts may be on effective water resource management. In order to achieve that latter goal, it is imperative that the methodologies by which such environmental impacts have been assessed and concluded are also undertaken. Sustainable development may be met with effective water resource management – that which takes into account the variety of factors that address the range of issues regarding dam and reservoir water use. It is towards that end that impacts must be contextualized and analyzed. Analysis of existing data Up to this point, the positive and negative impacts of dams have been briefly discussed. Reiterating them in further detail would be necessary to the main object of this paper, which is to analyze the implications of the impacts to sustainable water resource and dam management. Dams are built for a variety of purposes as mentioned above. One such purpose is to supply the downstream community with a reliable and consistent source of drinking water and water for irrigation (Duflo & Pande, 2007). This lessens the downstream communities’ dependence on rainfall and the maintenance of year-round irrigation system means increased agricultural productivity. Dams are also developed as means to control flooding. These two purposes have the added advantage of ameliorating the increasing risk and vulnerability to the effects of climate change; that is, some areas may be prone to drought while others may experience excessive precipitation and, thereby, flooding (Brown et al., 2009). Another purpose of dams is for hydro-generated electricity. There is growing condemnation of the use of coal-fired power plants and hydroelectricity is seen as an environmentally-friendly alternative, being categorized as a renewable source of energy (Sadler, et al., 2000). The impacts of dams differ because dams also differ with respect to their size, their other architectural system, the climate and environs of the location where it is situated, and its purpose (Sadler, et al., 2000). Size and location particularly are the key determinants to the magnitude and extent of its impacts on the environment. This has been underscored in the numerous case studies that evaluate the impacts of a particular dam with respect to pre-determined environmental variables for which baseline information are available. The most obvious and immediate impacts of dams would be the alteration of the water quality and quantity, sediment supply, and the change in landscape as the valley is inundated to fill up the delineated reservoir (Burke, et al., 2009). The effects of such changes results to further alteration and these have been the subject of several empirical studies in the past. Environmental changes range from the geophysical to the biological. Scientists have proven that the modifications on hydrology resulted to significant changes in bed mobility and stream morphology (Kondolf, 1997). In extreme cases, some rivers reportedly fail to reach and discharge to the sea at certain times of the year because of the series of obstructive dams it has encountered along the way. The transportation of sediments has also been altered, reducing the sediments that flow downstream, leading to downcutting and erosion of river banks and beaches (Kondolf, 1997). The physical changes also impact the biota and riparian vegetation. Several studies point to lessened recruitment of trees due to the fragmentation of riparian and sub-montane forests (Gordon & Meentemeyer, 2006). Another classic example is the effect on the breeding of migratory fishes such as salmon, whose passage back to their spawning and breeding grounds are blocked by massive dam structures (Tahmiscioglu, 2007). Ecologists are concerned that this has resulted to lessened productive capability and genetic isolation. The fragmentation of the landscape has also been shown to affect the distribution of insects (DUMC, 1998). Isolated patches of forests are especially vulnerable because the area may be less than what can hold a viable population. The loss of some insect populations can be expected to resound throughout the entire food chain of the forest and the entire ecosystem. Impact assessments have mostly been on a empirical studies or on a case to case basis, allowing for the distinctiveness of the case in each dam that was studied. While this has been invaluable in giving detailed information for specific locations and factors, the variability of project-based evaluation methodologies and results contributes little to the broader issue of making dam operations sustainable in the long term and is inadequate for the extrapolation of results that may be used to predict effects in other dams. Site-specific assessments must thereby give way to integrated and systematic models and methodologies that can be replicated, upscale, and extrapolated in different dam sites. Recent literature provides many examples but this paper will expound on two such methods with distinct purposes: (1) the application of hierarchal framework for impact assessment; and (2) integrative Dam Assessment Modeling Tool (IDAM). The application of a hierarchal framework for assessing environmental impacts of water impoundments and associated structure was put forward by Burke et al (2009). It took off from the concept that the impacts of dams are neither always immediate nor apparent but are cascading, complex, and inter-connected within a feedback loop. Burke et al (2009) proposed that environmental responses should be isolated and quantified based on the succession of impacts and analyzing the processes that link them. First order impacts are those that are immediately quantifiable as the direct results of modifications to the geophysical setting. Second order impacts are the physical changes that result from first order impacts while third order impacts are the influence of physical changes on biological changes; further feedback responses are considered fourth order impacts. Impact assessment is process-based and can be replicated in a variety of scenarios and covers a range of factors. IDAM is a tool for evaluating cost and benefits proposed by Brown et al. (2009); it thereby weighs positive and negative impacts equitably. Integrated to the cost/benefit analysis is the accounting of biophysical, socio-economic and ecological effects. It therefore allows decision makers to determine the priority concerns of constructing the dam and identify alternatives that would minimize the adverse impacts. IDAM is a systematic way of evaluating the impacts of a dam from a multi-disciplinary perspective, not just from one viewpoint or with respect to one or few variables. Conclusion and implications for evaluation The immediate and apparent impacts of dams are not the worst of its adverse effects on the environment. The various cascade effects and the feedback loops between physical processes and biological responses are complex, magnifying the impacts’ scope and severity. Project-based evaluations and empirical studies in the past have covered a variety of local settings but it has lost its currency (Sadler et al., 2000); what is needed is a holistic, systematic, and integrative approach for evaluating impacts on physical processes and consequent ecological functions. Process-based evaluation methods are more needed as they can be replicated across a wide range of variability while retaining the capability to isolate specific operational impacts. IDAM and the hierarchal framework provide the further advantage of allowing for process-based spatial and temporal extrapolations. Moreover, the multi-disciplinary integration of both negative and positive impacts that cut across economic, social and ecological concerns would give more objective results and aids in heuristic decision-making processes for dam planning, construction, and operation. The objectivity of process-based framework and methodologies in identifying effects will also help to make environmental impact assessment systems more effective and adequate for the purpose which they are intended. More importantly, the linkages between causes-effects and cost-benefits can be used to quantitatively assess future management strategies and conservation schemes. REFERENCE LIST Brown, P.H., Tullos, D., Tilt, B., Magee, D., Wolf, A.T. (2009). Modeling the costs and benefits of dam construction from a multidisciplinary perspective. Journal of Environmental Management, Vol. 90, SUP 3: S303-S311. doi:10.1016/j.jenvman.2008.07.025 Burke, M., Jorde, K., & Buffington, J.M. (2009). Application of a hierarchal framework for assessing environmental impacts of dam operation: Changes in streamflow, bed mobility, and recruitment of riparian trees in a Western North American river. Journal of Environmental Management, Vol. 90, SUP 3: S224-S236. Doi: 10.1016/j.jenvman.2008.07.022. Duflo, E. & Pande, R. (2007). Dams. Quarterly Journal of Economics 122 (2): 601-46. Duke University Medical Center (1998, August 14). Duke Studies Show That Environmental Effects Of Dams Extend To Insect Life. ScienceDaily. Retrieved March 7, 2010, from http://www.sciencedaily.com­ /releases/1998/08/980814070158.htm Gordon, E., & Meentemeyer, R.K. (2006). Effects of dam operation and land use on stream channel morphology and riparian vegetation. Geomorphology 82 (2006): 412-429. Sadler, B., Verocai, I., & Vanclay, F. (2000). Environmental and social impact assessment for large dams. WCD Thematic Review V.2 prepared as input to the World Commission on Dams, Cape Town, www.dams.org Tahmiscioglu, M.S., Anul, N., Ekmekci, F., & Durmus, N. (2007). Positive and negative impacts of dams on the environment. International Congress on River Basin Management, 22-24 March 2007, Antalaya, Turkey. Sachs, J. D. (2008). Common wealth: Economics for a crowded planet. New York: The Penguin Press. Read More