Analysis of Environmental Impacts of Dam Projects to Determine Optimum Alternative Case study : Kalat Dam and Hydropower

Introduction
Kalat Dam and Hydropower Plant, which is in Maroon River Basin, Kohgiluyeh and Boyer-Ahmad Province is situated in the southwest of Iran. In this research, in order to select the optimum alternative to this Project, with due emphasis on the environmental criterions, three alternatives, namely, Kalat, Sarkooh, and Zirna, are investigated. This plan encompasses the objectives of securing reserves, controlling flood, and producing hydro-electric power (HEP), which is currently studied, from the potentials of Maroon River waters. Table 1 illustrates the most critical technical specifications of the considered alternatives.
Table1: Technical specifications of the considered alternatives to Kalat Dam and Hydropower Plant Project
Dam Crest Elevation
(masl) Dam Height
(m) Reservoir Area
(ha) Reservoir Volume
(MCM) Alternative
830 130 2119 1313 kalat
1020 180 1339 704 Sarkoh
1070 170 751 423 Zirna
Materials and Methods
The studied area is located in Maroon River basin. The survey of soil erosion in the reservoir shows that the classification of erosion is not significantly intensive in the studied area. Thereby, from the viewpoint of erosion, the alternatives are in a desirable condition.
In the limits of the dam reservoir in Kalat, Sarkooh, and Zirna options, there are a number of 15, 8, and 2 villages which are located, respectively. Only within the limits of the reservoir of Kalat alternative, there exist two shrines and a historical bridge, which shall be submerged during the water-intake of the reservoir.
To determine the ecological capacity of reservoirs, slope, bedrock permeability, and density of vegetation, cover maps are used. Ecological model is classified into three groups: suitable, semi-suitable, and unsuitable. After overlaying the maps, the ecological capacity of the region is prepared.
In order to determine the optimum alternative, the analytic hierarchy process is utilized. The first step in this method is to create a structural formation at three levels, which are: Level 1- Objective: in selecting the optimum alternative, Level 2- Factors: in the way of criterions, and Level 3- Plans: considered for the selection.
To determine the criteria, check-list method is utilized. Subsequently, in accordance with the results of the check-list, the primary criteria are determined. In this research, by taking the environmental observations into account, 9 key criteria are selected.
In the second step, their weighting or coefficient importance is determined. To evaluate a criterion in relation to another criterion, a numerical value of 1 to 9 is taken into consideration such that two criteria, which are of an equal value, are evaluated numerically as (1). However, if the importance and priority in applying a criterion are infinitely more than those of another criterion, its comparative evaluation is considered 9 and the intermediate digits are determined based on the relative importance of the criteria.
In the third step, on the basis of the implication of the criterion coefficients and utilization of Expert Choice (EC) software, the weighting or significance of each of the indexes, relative to those of a higher level (relative weight), are computed. Such comparison and weighting are implemented in pairs between the criteria.
In the fourth step, the alternatives are separately compared in the form of pairs in each criterion and are weighed. However, in the ultimate step, by combining the comparative weightings of the alternatives and criteria, the final weighting of each alternative is calculated. Finally, the alternative that gains the optimum weight shall bear a critical degree of importance with respect to the other alternatives.
Discussion of Results
According to the results of assessment shown in Figure 1, ecological capacity map shows that 100% of Zirna alternative and more than 91% of Sarkoh and Kalat alternatives are located in suitable and semi-suitable zones. Because of different criteria, in order to determine the optimum alternative, multiple criteria decision analysis is utilized.

Fig.1: Ecological capacity map of three alternatives

In accordance with the basic studies and environmental conditions existing in the studied area, the environmental consequences of the plan are investigated in order to determine the environmental criteria (indices) using check-list method.
Based on the results obtained from the predicted impacts in Kalat, Sarkooh, and Zirna alternatives, it can be concluded that, despite the high importance of some criteria, they are not selected for determining selected criteria, since all the three alternatives have the same or similar conditions. Therefore, the most critical environmental criteria selected from the check-list method are: land use, threatened species of index flora having ecological value, index fauna, rural population centers, limits of the operational area influenced from the viewpoint of environmental destruction, land ownership, cultural heritage sites, other development plans and seismicity of sites.
In the subsequent phase, by utilizing Expert Choice software, the weighting of the criteria with respect to each other is mutually performed in such a manner that an increment in points, from 1 to 9, illustrates a more critical value in one criterion compared to another. In considering all the aspects and criteria, the alternative relative to Zirna, which has attained the highest points of 0.347, is the selected option, whereas the alternatives of Kalat and Sarkooh with the ranking of 0.339 and 0.314 points, respectively, are the second and third priorities. The results of comparison and points of the three alternatives demonstrate that the alternative of Sarkooh which has a noteworthy variation relative to the other two options has minimum points. The results attained in the developed model in the ‘Expert Choice software is demonstrated in Figure 2.


Fig. 2: Results of the final weighting of the alternatives in the ‘Expert Choice’ Software
Conclusion
Results obtained from this research illustrated that, in order to determine a choice of alternatives from the environmental point of view, conditions relating to land use, index flora, seismic conditions, and regional population specifications are of greater importance. Hence, they had an immense impact on determining the ultimate site. Comparison of the final points, which were determined for the three axes, showed that the sites of Zirna, Kalat, and Sarkooh, which attained 0.347, 0.338, and 0.312 points, respectively, gained the first to third priorities in terms of being selected for the dam location.
In the preliminary survey and without specifying the significant coefficients of the criteria, it seemed that, due to a few distinctions such as presence of accessible roads and less amount of damage to the reservoir, Sarkooh alternative gained the first preference for the dam construction, since, with the disclosure of all the major criteria in decision-making and bringing into consideration the critical coefficients as well as coupling comparison between the alternatives, it was specified that this alternative would be at farther distance than other options, ranking the last priority. Thereby, in all the projects in which a selection should be made between several alternatives which are subjected to numerous factors, it is essential to utilize appropriate multiple criterion assessment methods.
Finally, it is proposed that, since numerous dam and power plant projects are simultaneously studies or implemented in this basin, in order to prevent biased attitudes toward a specific project, strategic environmental assessment studies and regional planning must be performed.