Assessment of Environmental Impacts of Sangtudeh 2 Dam and Hydroelectric Power Plant Project

According to the criteria listed in section 4 of this paper and studies, surveys, field visits and interviews conducted in the project area and given the broadness of issues and factors in the region, only the important and influential environmental effects of Sangtudeh 2 Dam and Hydroelectric Power Plant were assessed. The results are shown in Table 4, Table 5, and Table 6 and the final score and result of environmental assessment of this project is presented in Table 7

7.1. Assessment of Environmental Impacts of Sangtudeh 2 Dam on Physical and Chemical Resources Table 4: Important physical and chemical impacts in the project area

(a) Electric power generation and flood control +3 5 +15

(b) Water sources including quantity, balance, and regulation of the ground discharge regime in

the project area +3 4 +12

(c) Water sources including the quality of surface discharge in the upstream and downstream of

the project area -2 4 -8

(d) Soil erosion and subsidence -2 3 -6

(e) Induced earthquakes and landslides -1 3 -3

(f) Deposits, materials, and solid particles in water -2 4 -8

(g) Groundwater level changes -2 3 -6

(h) Construction of power transmission lines and water diversion channels -1 2 -2

(i) Disposal of wastes, sewage, and construction debris -1 1 -1

Sum of the assessment scores -7

(a)- Electric power generation and flood control:

Dams are structures that are built for storing surface water and the water stored behind dams can provide various purposes such as flood control, electricity generation, drinking water, agriculture water, etc.

Many dams are multi-purpose and are used simultaneously for different purposes. Sangtudeh 2 Dam and Hydroelectric Power Plant is no exception and have many applications. One of the most important goals of this project is to generate electricity using the water stored behind the dam. Having two power plant units, Sangtudeh 2 is capable of producing 220 megawatts of electricity (110 MW in each unit). Due to the pervasive consumption of electricity in various industrial, urban, and agricultural sectors of Tajikistan, increasing the generation of electricity is one of goals of Tajikistan's government and the establishment of Sangtudeh 2 has played an important role in this regard. Hence, the impact of mentioned positive processes and their impact range were considered "high" with a score of +3 and their impact importance was considered "very important" with a score of 5.

(b) And (c) - Water sources including quality, quantity, balance, regulation of the surface discharge regime in the project area: With the construction of a dam and the storage of surface water behind it, some changes will occur in the quality, quantity, and surface discharge regime in the region.

Changes in water quality include sedimentation, thermal stratification in the lake, water turbidity, smelly lake water, and changes in water quality in the upstream and downstream of the dam.

This part is considered among negative environmental process of dams and it is predicted that the resultant of impacts on surface water quality within Sangtudeh 2 project is negative and impact range of this process is now cautiously considered negative with a quality of medium and a score of -2

quantity and balance and surface discharge regime within the project, during the field visit, it was observed that the large and permanent river of Vakhsh, with an annual average bring of 20,500 million cubic meters and average annual discharge of 631 cubic meters per second, is flowing and considering the discharge of this river, the construction of Sangtudeh 2 will have no negative impact on quantity and surface discharge balance in downstream and other dams can be built in the downstream of this river. For example, Sarband, Perepadnaya, and Central dams were built in the downstream of Vakhsh River before the construction of Sangtudeh 2 for power generation and other uses. So, impact range in quantity and surface water balance within Sangtudeh 2 project is evaluated with a quality of high and a score of +3 impact importance is assessed with a quality of very important and a score of 4.

(d)- Soil erosion and subsidence:Soil compaction and subsidence in many development projects is due to the operation of vehicle in the construction phase. The importance of compaction is due to the reduced water penetration to feed the plant roots and also enclosure of water in one place.

Soil erosion increases during the various stages of excavation and due to the rummage of soil.

In Sangtudeh 2, like other earth dams, excavation and digging stages have been done in the river and the surrounding area. The volume of excavation and embankment were equal to 1396016 and 585,346 cubic meters, respectively. Considering the volume of soil operation in the project area, impact range of this process was evaluated negative with a quality of medium and a score of -2 and its impact importance was assessed important with a score of 3.

(e) Induced earthquakes and landslides: Factors such as tank condition, the rise in water level, impoundment duration, geological characteristics and existence of fault or cracks, duration of maintaining the water in highest level, discharge of tank in one time, and earthquake risk in the region can cause the abnormal internal pressures in the land and the outbreak of induced earthquakes. Given the earthquake risk and existence of faults and cracks in the region and also the volume of collected water behind the dam which is equal to 66.5 million cubic meters, induced earthquake prediction in the project area is acceptable. On the other hand, due to the need to have a suitable height of water behind the dam to turn the turbines of plants and generate electricity power, tank volume should always have an acceptable utilization capacity and consequently, the water collected behind the dam will not be discharged once.

So, sudden changes in water level of the lake of Sangtudeh 2 Dam is low and the effect of induced landslides and earthquakes would be less. Also, no induced earthquake has been reported in the project area. Hence, impact range of this factor was evaluated negative with a quality of low and a score of -1 and its impact importance was assessed important with a score of 3.

(f)- Deposits, materials, and solid particles in water: Construction of a dam reduces the flow rate of a river when entering the dam's reservoir and due to the trapped surface flows behind the dam which contains suspended particles, solid materials, and sediments, according to Stokes law and with the deposition of particles, suspended and solid materials in the bed of the dam's lake, sedimentation process will occur. Sedimentation in reservoirs of dams is the most important factor threatening the large hydro projects and has many negative effects such as reduced the efficiency, water volume, and capacity of reservoir behind the dam; reduced amount of water needed for various purposes in the downstream of dam; loss of nutrients in downstream; pollution caused by deposition of organic and putrescible materials in reservoir; water turbidity; and consequently pollution and long-term changes in the ecosystem of region. Sangtudeh 2, with a maximum height of 31.5 meters, is one of the large dams according to the classification of International Committee on Dams (ICOD).

As a result, more water can be collected behind this dam, but accumulation of solid and suspended materials in the Vakhsh River, especially in the time of snow and ice melt in mountains and higher concentration of sediments decrease the volume of water and reservoir capacity.

This put the main purpose of the dam to generate electricity at risk in the long term which is a negative environmental impact to the dam. There are four other dams in the course of the great river of Vakhsh and in the upstream of Sangtudeh 2 Dam named Rogun, Nurek, Baipazi, and Sangtudeh 1 in order from upstream to downstream. Rogun Dam is being constructed and three other are operating.

(A Case Study: Dam and Hydroelectric Power Plant of Sangtudeh 2 in Tajikistan) 140 Presence of these dams in upstream reduces the volume of solid materials and particles in the water of river resulting in a lower volume of sediments accumulated in the reservoir of Sangtudeh 2 Dam. So, the resultant impact of the deposition process in this dam predicted negative with caution. Impact range of this process was evaluated medium with a score of -2 and impact importance was assessed very important with a score of 4.

(g)- Groundwater level changes: Reservoir and hydroelectric dams, due to having large volume of water behind the dam, have the greatest impact on groundwater levels. Construction of dams decreases the supply of underground water in downstream.

However, dams can strengthen and increase the level of groundwater indirectly, through watershed measures, or directly in the region influenced by the dam's lake. When the level of groundwater is high and close to the ground, the salt of soil is taken to the ground by capillary process and making the farms salty.

Even when the use of groundwater is properly controlled, low quality of groundwater may lead to secondary salinity. Land salinity causes low efficiency of salt-sensitive crop and non-productivity of lands. This process has both negative and positive effects. Given that Sangtudeh 2 is a hydroelectric dam with a maximum reservoir capacity of 66.5 million cubic meters, the resultant of this process was predicted negative with caution in this study. Impact range of this process was evaluated negative with a quality of medium and a score of -2 and its impact importance was assessed important with a score of 3.

(h)- Construction of power transmission lines and water diversion channels: Since Sangtudeh 2 is a hydroelectric dam which generates electricity using the power of water collected behind the dam; it is needed to connect the generated electricity to the national power grid of Tajikistan. In Sangtudeh 2, this is done by construction of an electricity power transmission station next to the site of dam and in the downstream.

Activities such as construction of power transmission lines and water diversion channels, either during the construction or during the operation of dam and powerhouse, usually cause negative impacts due to various physical and chemical contaminants entering the river. Hence, impact range of this process was predicted negative with a quality of low and a score of -1 and its impact importance was assessed low with a score of 2.

(i)- Disposal of wastes, sewage, and construction debris: Construction debris, solid wastes, and wastes of facilities and planthouse in different executive phases entering the river and pollutants, sewage, and industrial, urban, and rural waste created during the operation phase are considered negative environmental impacts of dams.

During the field visit of the project area in Sangtudeh 2 Dam, no significant negative impact caused by industrial, domestic, and agricultural waste on the quality of inlet and outlet water of the lake (downstream and upstream of the dam) were observed. So, this process can be predicted negative.

Impact range of this process was evaluated negative with a quality of low and a score of -1 and its impact importance was assessed very low with a score of 1.

7.2. Assessment of Important Environmental Impacts of Sangtudeh 2 Dam on Sanitary and Biological Resources

Table 5: Biological and sanitary effects in the project area

(j) Ecosystems and habitats +1 4 +4

(k) Weather and climate changes -1 4 4-

(l) Surface water, their uses, outbreak of diseases, and increased insects -1 3 -3

Sum of scores -3

operation always has direct and indirect positive and negative impacts on ecosystem and natural habitats in the project area.

Vakhsh River ecosystem also includes vegetation and the habitats of a variety of aquatic non-aquatic organisms in the catchment of the project area that will face changes by the construction of this dam. In the implementation phase, due to changes in the course of river and operations such as excavation, embankment, digging, removal of material from the river bed, and so on, salts and solids are accumulated in upstream and downstream of the dam and this causes changes in water quality, discharge rate, regional ecosystem, and animal habitat in the catchment of the project area.

In the operation phase, water storage behind the dam can create a variety of plant and animal habitats in upstream and downstream of the dam. It is predicted that the catchment of Sangtudeh 2 Dam will have new animal and plant features and conditions. Given that the time of operation of Sangtudeh 2 Dam is about one year, the resultant of positive and negative impacts on ecosystem of the project area in two implementation and operation phases is predicted positive. Impact range of this process was evaluated positive with a quality of low and a score of +1 and its impact importance was assessed very important with a score of 4.

(k)- Weather and climate changes: The impacts of dams on climate of the region are one of the most important issues. The lakes behind the reservoir dams cause changes in the micro climate of region around the lake, so that the mean annual temperature is increased and the area has a climate with more humidity.

Additionally, the volume of water added to the atmosphere (evaporation) can affect the temporal-spatial distribution of precipitation and its amount if other required factors are present. These effects would be true to the area of Sangtudeh 2 Dam. Given the average annual evaporation from the dam's lake (which is equal to 1457 mm) is added to the atmosphere of the region, it is expected that the region will have a climate with higher humidity and this causes an increase in mean annual temperature and precipitation in the region. All these factors altogether tangibly change the climate conditions in the limited catchment of the dam. Given that the time of operation of Sangtudeh 2 Dam is about one year, the resultant of this process's effects is predicted negative.

Impact range of these changes were cautiously evaluated negative with a quality of low and a score of -1 and their impact importance were assessed very important with a score of 4.

(i)- Surface water, their uses, outbreak of diseases, and increased insects: Construction of a dam and storage of surface water behind the dam in an area called the dam's lake will definitely have effective impacts on surface water in upstream and downstream of the dam. Negative health effects resulting from the lake are part of these impacts that their impact range, durability, advance range, and effects on different water consumptions especially in downstream should be assessed. These negative aspects will have adverse impacts on health of humans, plants, animals, and natural environments and provide the condition for the spread of contaminations and proliferation of diseases vectors.

Water retention behind the dam causes sedimentation, turbidity, and smelly water in the dam's reservoir and this leads to microbial contamination of reservoir water. Parallel to this, spawning and propagation of insects in the lack of dam and prevalence of pathogenic bacteria also increase the contamination. All these factors will have a significant impact on water consumptions in different sectors, especially in downstream of the dam. During a field visit to Sangtudeh 2 Dam, it was found that this dam is a flowing dam because the continuous rotation of turbines of power plant using the water collected in reservoirs is needed to generate electricity.

So, water retention in the lake of this dam is not long and since the discharge of Vakhsh River is 631 cubic meters per second, there will be a acceptable balanced discharge in downstream in all seasons. It is expected that these will reduce and mitigate the negative health effects of previously mentioned factors in the area. Given that the time of operation of Sangtudeh 2 Dam is about one year, impact range of this process was cautiously devalued negative with a quality of low and a score of -1 and its impact importance was assessed important with a score of 3.

(A Case Study: Dam and Hydroelectric Power Plant of Sangtudeh 2 in Tajikistan) 142 7.3. Assessment of Environmental Impacts of Sangtudeh 2 Dam on Economic, Social, and

Cultural Resources

Table 6: Important economic, social, and cultural impacts in the project area

(m) Culture of fish, aquatic organisms, and birds + 1 +4

4

(n) Tourism industry, employment and income, and economic prosperity +2 + 8 4

(o) Residents migration and displacement of people and degradation of lands,

pastures, and vegetation +2 +8

4

Sum of scores + 20

(m)- Culture of fish, aquatic organisms, and birds: Constructed over Vakhsh Rive with a height of 31.5 meters from the river bed, Sangtudeh 2 has the capacity to store 66.5 million cubic meters behind its earth wall. The lake created behind this dam is located in a mountainous region with an average altitude of 1800 to 2000 meters above sea level and has created a valuable and suitable habitat in the region that, in addition to attracting waterfowls, can also be a good place for aquaculture.

Generally, it is expected that the lake of Sangtudeh 2 Dam will be a new and suitable habitat for the culture of fish and waterfowls in the project area. Impact range of this process was evaluated positive with a quality of low and a score of +1 and its impact importance was assessed very important with a score of 4.

(n)- Tourism industry, employment and income, and economic prosperity: Implementation and operation of a dam always make important effects and changes in urban and rural communities and also in social, economic, and cultural relations of the project area. In the implementation phase, some changes are made in the region with the arrival of non-native and native labor force with different social and cultural characteristics and purchase of the staff requirements, preparing and buying the equipment, facilities, and materials needed to build the dam, and other services and affairs related to the construction of dam can lead to economic prosperity in the region.

Operation phase of dam will have long-term social, economic, and cultural effects. In fact, with beginning of impounding and storage of surface flows behind the dam structure, beautiful sceneries will be created that provide the condition for recreational and sports activities such as boating, fishing, swimming, and so on. Also, investment in recreation centers can cause the growth and development of tourism industry and thereby economic, social, and cultural development in the project area. During the field visit to Sangtudeh 2 project area. A variety of rural and urban population centers.

Ghazangozar village near the dam site, Sarband city at a distance of 13 km from the dam site, and Gharghantapeh city (the center of Khalton) at a distance of 28 km from the dam (114 km from Dushanbe, the capital of Tajikistan) are of important cities and industrial, social, and cultural centers of Tajikistan.

Located in the project area, these cities can play a significant role in economic, social, and cultural development and growth of region and the project area both in the implementation and operation phases of Sangtudeh 2. So, impact range of this process was evaluated positive with a quality of medium and a score of +2 and its impact importance was assessed very important with a score of 4.

(o)- Residents migration and displacement of people and degradation of lands, pastures, and vegetation: Since the beginning of dam construction and water storage behind the dam, some problem such as destruction of farms, rural lands, and vegetation in the region and migration of residents to other regions and neighboring towns will emerge.

Studies show that in the absence of proper planning for population displacement,

Studies show that in the absence of proper planning for population displacement,