Chapter 1: introduction
Additional Arrangements for Religious and Cremation Requirements
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- Prohibition on Fishing and aggregate mining in the Dewatered Section in the Dry season
- II. Impact on fish migration and spawning areas of fish in the Kabeli River Upstream of the weir
- The Fish Trapping, Hauling and Release alternative
- The Fish Ladder
- species annually in the upper catchment of the Kabeli is the other alternative. But this alternative will require
- Experience of cold water fish hatchery in Nepal (Kali Gandaki “A”, Pokhara, Trishuli, and Godavari) reveals that the target
- An analysis of the various options reveals that the
- III Impact of Fish Entrapment in Headrace Tunnel and Turbine Impact
- IV. Impact of KAHEP on the Tamor River Impact
- Table 6.12: Hydrological Change in the Tamor River (between Kabeli – Tamor confluence and Kabeli tailrace outlet) due to KAHEP
- Months Tamor at KAHEP Powerhouse Site (m 3 /s)
- Table 6.13: Hydrological Fluctuations in Tamor River in Non-operation and Peaking Operation Periods
- Tamor River Hydrology Peaking Operation Periods (m 3 /s) Percentage
- Table 6.14: Water Levels in the non-operating and peak Operating periods in Tamor River
- Peak Operation ((m amsl) Water Level Difference (m)
- Summary of the predicted impacts for primary environmental issues are presented in Table 6. 15 below.
- Note: D = Direct, ID = Indirect, S= Site specific, L= Local, R= Regional, ST=Short Term, LT= Long Term, H = High, M=Moderate, LO= Low
Additional Arrangements for Religious and Cremation Requirements The proposed Downstream Flow is assumed sufficient for the general sanitation of the river stretch where the general non-consumptive use is limited to a few numbers of people. But, in the river stretch where a large number of people will gather and perform religious and cremation as in the Kabeli temple and in the cremation grounds, the dispersed natural flow may not be able to maintain the sanitation conditions of the used river stretch. To maintain cleanliness of the river bed and to provide adequate water to the users the water flowing in the river will be canalised in the month of November every year for funeral rituals at the cremation sites of the river. Similarly suitable ponds of waist height will be established in the dry season at the Kabeli Temple site for religious baths. The project will built structures like check dams as necessary along its cremation area sites to create pools and will also carry out regular cleaning operations in order to make the river bed clean and healthy. In the religious festival day additional water than the environmental flow will be released to maintain the river bed sanitation. These measures will be included in the EMP.
Low flow conditions will be limited only to environmental flow releases in the dry season (November through May) and could potentially trap adult fish in isolated pools. This low water conditions may be regarded as favourable for fishing. As the ecological areas for the available fish species in the dewatered section is greatly constrained due to reduction in flows, existing fish species of the dewatered stretch have little area to hide and run away and will be trapped easier by fisherman. Therefore, to protect the thriving fish species in the dewatered stretch in the dry months; fishing in dry month will be prohibited in the dewatered section. Such prohibition will be carried out in cooperation with the local people and fishermen through awareness programs and employing some of the fishermen to regulate prohibition provisions and report fishing activities to the project and to the local regulating authorities for timely actions. b. Change in the composition of the fish species in the reservoir section Impact From November through May, a reservoir will be maintained at the upstream barrage of the KAHEP as per the operation plan of the project (refer section 2.9, Chapter II). While from June through October the river will be left open to flow in its natural conditions. The aquatic life of the Kabeli river is represented mostly by cold water fish adapted to free flowing conditions in a highly oxygeneated environment. Since the water above the barrage will be a big pool for a stretch of about 1.3 km, some of the fish speices are likely to be driven away from the reservoir stretch to upstream sections which will constrain the feeding, rearing, and spawning grounds of these species.Other species might find the reservoir as a more favourable habitat. As very little is known about the ecological status of the aquatic life of the Kabeli, it is difficult to predict the extent of the impact to the resident and migratory aquatic species to the changed flow regime and water qualityconditions. Considering the short water retention period with daily fluctuation of water level from minimum to maximum depth twice a day and reservoir being filled by highly oxygenated water in a shallow water environment for most part of the reservoir, it is envisaged that the impacts related to low dissolved oxygen will be considered to be low and insignificant to the majority of the aquatic life. Similarly, the intermitent shallow water reservoir conditions is not likely to drive away the shallow water loving fishery of the river as the reservoir also provide habitat of the pool like environment of the unregulated river. Mitigation This impact is expected to be insignificant as explained in the previous paragraph. Only option to avoid this potentially minor impact to aquatic life from the reservoir water condition is to design the project as run-off-the-river option and forego the benefit of peaking power from water regulation in the reservoir in the dry season. Since this option is not economically beneficial and the risk to fish/ aquatic life is low, no action will be taken to mitigate the impact. The impact resulting from the reservoir formation to aquatic life will remain as residual impact of the project throughout the project life. However, aditional fish mitigation and compensation measures are included in the EMP (fish hatchery, functional intact river strategy). c. Reservoir eutrophication and associated impacts to aquatic life Impacts The catchment of the Kabeli river is composed of a number of rural settlments and agricultural fields that becomes the potential source of the phosphorous and nitrogeneous waste from sweage of man and animals and also release of agrochemicals from agriculture.Since KAHEP will have a small daily regulation reservoir, with a short retention time, any detectable sign of euthrophication is unlikely, however, water quality measurements will be part of the EMP. Even in the present conditions, algal blooming in the detached pool sections in the river have been observed in the Kabeli River. Such algal blooming in the reservoir section could not be completely ruled out. If such eutrophication occured due to increased concentration of phosphorous and nitrogen, it canhave effect onthe fresh water aquatic life with possiblefish diveristy implications. As stated above, the operation mode of the reservoir regulation, however, does not allow long period retention of the water hence limiting the chances of increase in the concentration of phosphorous and nitrogen and it is more likely that the eutrophication will be an issue of minor significance in the reservoir. Mitigation Water quality in the reservoirs and algal bloom and aquatic weeds will be monitored. If eutrophic conditions are detected and algal blooms are present, the following measures will be implemented as necessary.
II. Impact on fish migration and spawning areas of fish in the Kabeli River Upstream of the weir The dam height of 14.30 m constructed across Kabeli River will potentially avert the upstream migration of migratory fishes namely Tor Putitora (Sahar), Schizothorax richardsonii (Blunt–nosed Asala), Schizothoraichthys progastus (Pointed nose - Asala), Neolissocheilus hexagonolepis (Katle) and Labeo dero (Gardi). These fishes migrate to upstream areas of Kabeli River for spawning and move downstream for feeding. Further Tor Putitora (Sahar) and Schizothorax richardsonii (Blunt–nosed Asala) are included as the endangered and vulnerable species in the IUCN red list of 2012 respectively. Refer 4.3.3.6 for description of fish of conservation significance in KAHEP. Upstream migration of the fish in the Kabeli, and in the Tamor as well, is not well understood. The literature rivew of the cold water fish populations in the major Himalayan rivers and consultation with the local part time fishermen suggests that upstream migration of the fish start from June till September. The peak upstream migration is in June, July and August and downstream migration is in October through November. Some species might migrate upstream during low flow season. Thus, if unmitigated, the construction of the dam will restrict the migration and reduce the population and diversity of Kabeli River in the long run. This is one of the potential significant impacts to the fish populations of the Kabeli River.Studies conducted elswhere have indicated that the diversion structures on a natural river, if unmitigated can cause a loss of nearly 60% of the fish habitat with a long term effect on the fish population. Furthermore, the migration patterns of fish in the entire Tamor river watershed are also not fully known. Apart from Kabeli, other tributaries like Mewa Khola and Hewa Khola that have similar river characteristics are in the Tamor basin and the migrating fish have alternative migration routes. Fish monitoring efforts will be necessary to assess impacts and residual impacts on fish migration in the Tamor watershed. This monitoring effort will be included in the EMP.
To assess the reported diversity composition of the fish species an additional sampling study during early stages of construction and during operation will be carried out. The sampling will commence during monsoon 201313 and will be done at least four times in the first year to capture four seasons and then twice a year to cover dry and monsoon until the fifth year of operation. The potential sampling sites are:
There are various options to mitigate the effects of restriction to fish migration due to diversion dam, however, the effectiveness of the applied measures may be quite different for the different measures depending upon the local field conditions, behavior of the existing aquatic fish species etc. Commonly used mitigation options are:
The Fish Trapping, Hauling and Release alternative is cost effective, labor intensive and provide direct benefit to the local economy as this will be based on the employment of the local fisherman community. For the trapping of fish, various fish traps can be used. The commonly used fish traps for upstream and downstream migrant fishes are bamboo weir fish traps, fish wheels, fyke or Hoop Nets and pot gears. The trapped fish then can be hauled using transportation vehicles. To transport the fish upstream and downstream, specially designed insulated water tanks with facilities for aeration and water circulation will be needed. Such tanks can be designed and manufactured in Nepal. The only drawback of this option is that the handling of the fish during trapping and hauling may result in high mortality of the fish. The Fish Lock Alternative is the automated mechanical device designed and placed in the dam structure. A special fish lock structure below, above the dam attracts, and lock the fishes. The locked fishes are then hauled across the dam by a specially designed lift automatically. Such devices have been brought into operation at number of dams in other parts of the world. Owing to the fish release conflict, difficulties in attracting fish in the lock area and difficulty for fish to access the trap area in the turbulent water condition released from the spillway in monsoon, this alternative may not function effectively at times when it is required the most. The Fish Ladder Alternative provides a natural migratory path to the migrating fish without human intervention in the migrating season. Since very little is known on the swimming speed of the targeted fish species and required flow condtions of water, it is difficult to design an effective fish ladder. As dam height is low, a fish ladder constructed with a few pools and sections designed as a small riverbed could be a better option in the case of Nepal. On site cold water fish hatchery annexed with open water stocking of mid-range and long distance migrant species annually in the upper catchment of the Kabeli is the other alternative. But this alternative will require maintenanceof a on site fish hatchery of the targeted fish species for the production of the targeted numbers of fingerlings from hatchery and hauling of the fish fingerlings for open water stocking in the Kabeli River. Experience of cold water fish hatchery in Nepal (Kali Gandaki “A”, Pokhara, Trishuli, and Godavari) reveals that the target14 fish species including the IUCN red list species could be breed in the hatchery in captivity. This option though costly in terms of infrastructure and operation investments has advantages over the other options as it ensures the conservation of the IUCN red list species in the Kabeli River, and may even conserve the native species that have been recently caught in the Kabeli, such as the Kabre. An analysis of the various options reveals that the Fish Trapping and Truckingand Fish Lock Alternativesare relatively cheap and do not require high investment costs compared to fish ladder and cold water fish hatchery alternatives but would require an effective and efficient management throughout the project operation period. The effective and efficient management in the context of Nepal is highly questionable. Therefore the fish ladder alternative in combination with the on- site cold water fish hatchery annexed with the open water fish stocking are the best alternatives in the case of the Kabeli River to minimise the barrier effect to fish migration vis-á-vis conservation of the IUCN red list speceis. Such a combination of fish ladder and fish hatchery is also expected to overcome the uncertainity of the effective functioning of the fish ladder, which itself is a subject of study and research in Nepal.The fish ladder will facilitate upstream migration of the fish speceis in the Kabeli River. To find an optimal and functional design, modification in the latter stage of project operation will be made as a part of adaptive management strategy based on site monitoring results. Apart from this, the cold water fish hatchery will compensate for some of the impacts on fish diversity and population of the upstream Kabeli River. In the downstream section, the habitats provided by the Tamor River are anticipated to mitigate the impacts on fish diversity and population. Therefore, as mitigation to the barrier effect, the project dam design will incorporate a suitable ladder after examining the effectiveness of the various ladders in use in Nepal or in the region. The downstream flow will be released from the fish ladder for all times during project operation. Estimated cost for the fish ladder is NRs.56,99,914.00 which is included in the civil costs. Summarizing, in addition to the fish ladder, the project will provide an onsite cold-water fish hatchery for a selection of the migratory fish species including the IUCN red list species and operate the fish hatchery for the production of fish fingerlings for open water fish stocking in the Kabeli River. A separate study, included in the EMP, for the establishment and operation of the cold water fish hatchery will be undertaken in the initial phase of project construction period based on the experience of the cold water fish hatchery in Kali Gandaki “A”, Pokhara, and Trishuli. Estimated cost for the fish hatchery study and establishment is NRs 10 million. The cost of operating hatchery will be borne by the developer.
The fish assemblage of the Kabeli River comprises of resident and migratory fish species (Table 4.30, Chapter IV). The resident species as they are small sized fish with low sport value are not subjected of harvesting by locals. These species are distributed both upstream and downstream of the Kabeli diversion structures and considered resident or non-migratory in behavior, the effect of entrapment to the resident species in the headrace tunnel and turbine will have a limited localized impact for the fish population inhabiting the reservoir areas only. Therefore, the impact is considered as of low significance. The migratory fish (Table 4.30 Chapter IV), on the other hand, found in the Kabeli River are reported to have behavioral characteristics similar to that of anadromous species i.e. these fish migrate upstream from the downstream areas for spawning in the headwaters and return back to the downstream areas and remain in the downstream areas till the next spawning season. Entrapment of these species at the headrace and intake tunnel is likely in the process of downstream migration, and they may be sucked through the turbines while migrating downstream, with consequent potential mortality effects. The envisaged effects could have long term implications on fish population. Literature review and consultation with local fishermen reveal normal downstream fish migration starting towards the end of September and continues through December, the peak downstream migration is in October. The available flow in October is larger than the KAHEP design discharge whereas in the months of November and December the available discharge is less. Therefore, the risk of fish entrapment in the turbine is considered higher for the migratory species in the months of November and December than in October. In these months, the only available discharge through the diversion structure is the environmental flow that will be released through the fish ladder structure. Mitigation Nearly thirty migration devices have been tested over the past 50 years (Therrien, J et al. 2000). These devices are grouped in four main categories: bypasses, physical barriers, behavioral barriers and trapping and transportation systems to avoid fish trapping into the headrace structures and to the turbine. The KAHEP will incorporate a surface spill in its barrage design to release the EF through a fish ladder. The EF will be released throughout the project life and it is envisaged to also function as a bypass structure for the migrating fish downstream in the low flow season. During the high flow periods or periods when the design flow of the KAHEP is lower than the available Kabeli River flow (June, through October), the opening of the radial gate of the barrage in addition to the fish ladder structure will provide pathways for the downstream migration. The company is evaluating different options to avoid fish entrapment into the desanding basin and subsequently to the headrace tunnel and turbine in the KAHEP waterways. One option being considered is to build the fish ladder on the right bank of the dam where KAHEP is also considering to construct a fish friendly spillway. To construct the fish ladder at the right bank is expected to reduce the risk for up migrating fish to be trapped in the tunnel inlet as soon as they enter the reservoir. Alternatively, these structures may be built on the left banks but in addition to fish friendly spillways and physical barriers, the water velocity at the intake will be kept at less than 1 m/s to avoid entrapment of upstream migrating fish when they enter the reservoir. Envisaged mitigation cost for this arrangement is about NRs 3.5 million.
The KAHEP operation will impact Tamor River hydrology in two ways. First, there will be overall reduction in the Tamor River hydrology in the stretch between Kabeli – Tamor confluence and Kabeli tailrace outlet, and second there will be hydrological fluctuation on Tamor River due to operation of the plant at peak demand/hours (2 hrs in the morning and 4 hrs in the evening) during low flow season (November through May). The Tamor River flow at the downstream of the tailrace outlet will be influenced significantly by the water release during the peaking operation (6-8 AM and 6-10 PM). The stretch of Tamor River between Kabeli – Tamor confluence and Kabeli tailrace outlet will experience reduction in the existing Tamor River hydrology due to water diversion by KAHEP. Table 6.12 presents the expected average hydrological reduction in this affected stretch. Table 6.12: Hydrological Change in the Tamor River (between Kabeli – Tamor confluence and Kabeli tailrace outlet) due to KAHEP
Source: KEL 2012 The hydrological reductions are significant in the non-monsoon months (November to May) with maximum in the month of May. In the monsoon months, the hydrological difference will be minimum and vary between 15 and 5 percent of the existing average monthly flows. Since sufficient water is available in the affected stretch of Tamor River, the impact of the hydrological reduction to the aquatic ecology and other goods and services of the stretch’s Tamor River hydrology is envisaged to be insignificant. Secondly, the KAHEP operation in the dry season (November through May) with daily peaking and non-peaking operations is expected to bring noticeable changes in the Tamor River hydrology with fluctuations on the river hydrology and water levels downstream the tailrace. Table 6.13 presents the expected fluctuations in the Tamor River hydrology in the non-operation and peaking operations. Table 6.13: Hydrological Fluctuations in Tamor River in Non-operation and Peaking Operation Periods
KEL, 2012 Daily water fluctuations above 100 percent of the non-operation periods hydrology in the Tamor River are expected, maximum being in the month of March with over 160%. Such a fluctuation in the river hydrology daily is of concern to the aquatic ecology as well as the river safety and goods and services of the downstream riverine communities of Tamor River which are analyzed in the paragraphs below. Studies conducted in the flow regulated sites with pulsed water releases for peaking power generation, particularly in the low water periods, have indicated severe reduction on habitat persistency (Freeman et.al, 2001). The most marked effect of this kind of peaking activity is the phenomenon stranding which means that macro-invertebrates and fish can be trapped in the gravel when water flow undergo rapid decrease. The effects depend on the cross-section profile, the gravel bed composition, the fluctuation nature and the species of macro-invertebrates and fish present. If the shorelines are flat with low angle of inclination, the stranding effect is higher than if the angle of inclination is high. These stranding effects are normally seen as the most serious environmental consequence downstream of a peaking power station. In Nepal these effects are not studied and due to the fact that the effects are species specific, it will be of high value to do monitoring work and to design a study on these topics as part of the EMP. The most critical situation is the decreasing flow. A fast decline in flow will give the small fish and macro-invertebrates small chances to escape. Normal reaction for small fish is to hide into the gravel when a frightening situation occurs. Corse gravel give good shelter and high mortality while fine sand gives bad shelter and low mortality. Bigger fish is normally able to escape. One of the physical consequences of hydro-peaking is erosion which depend on gravel properties, angel of shore line inclination and how rapid the rise and fall in water levels occur. This erosion effects will normally be of high grade the first years after start of the hydro-peaking and then the effects will be reduced as a consequence of riverbed stabilization. Knowledge of effects from hydro-peaking on fish is mainly developed on salmonids and detail effects and mitigating measures are probably impossible to transfer to Himalayan rivers. For salmonids, results of experiments show that reduction of the rate of water level to less than 13 cm per hour will give significantly reduced risk for stranding. But, as already expressed, this guideline might be misleading in Himalayan rivers, where fish may be better adapted to natural torrential rivers and drastic daily flow fluctuations from both snowmelt and monsoon season. Hydro-peaking daily fluctuations may also affect local habitats in the discharge fluctuation zone. It has been reported that hydro-peaking may affect shallow water spawning habitats, especially if the fish assemblage spawns during such high hydrological fluctuation periods. A hydro-peaking zone in a regulated river will also normally give unstable hydraulic conditions that will affect the ecosystem and probably normally cause reduction in productivity. The KAHEP induced changes in the Tamor river hydrology during the dry season is likely to have the similar impacts for at least 2 to 3 km downstream from the KAHEP tailrace. Further downstream pulse effect of the water release is expected to decrease and the river will naturally neutralize the pulse effect as it moves downstream. The other impact of the hydrological fluctuation envisaged is the safety and goods and services issues of the downstream riverine communities. Like Kabeli, Tamor River downstream to the KAHEP tailrace is not used for consumptive uses. The religious and recreation uses, including fishing, is the only goods and services provided by the river to the riverine communities. The expected change in the water levels in the Tamor River in the operation and non-operation period is less than 0.42m in the dry season and less than 0.2m in the monsoon season (Table 6.14). Expected rise in the water level will have a time lag of nearly 20 to 30 minutes, and there will be sufficient time for the communities using the Tamor River to move to safety in areas immediate to the tailrace outlet. However, warning devices are warranted. Further downstream, as additional tributaries add to the Tamor hydrology, these impacts of safety are expected to gradually decline. Table 6.14: Water Levels in the non-operating and peak Operating periods in Tamor River
KEL 2012 Mitigation The anticipated hydrological change in the Tamor river stretch between Kabeli-Tamor confluence and the Tailrace outlet will be a residual impact of the project, though significant impacts of the hydrological changes is not anticipated in the stretch. Impact of hydrological fluctuation downstream of the tailrace on the aquatic ecology of the Tamor River particularly to the fish juveniles at this level of project planning is not clearly understood but might be considerable. However, monitoring of the downstream river stretch for the envisaged impact is needed for the formulation of future adaptive management strategy in order to identify additional mitigation and management measures. To mitigate the potential impact of the hydrological fluctuations in the dry season to the riverine communities following measures will be implemented.
Summary of the predicted impacts for primary environmental issues are presented in Table 6.15 below. Table 6.15: Summary of the Primary Environmental Issues - Impact Prediction
Note: D = Direct, ID = Indirect, S= Site specific, L= Local, R= Regional, ST=Short Term, LT= Long Term, H = High, M=Moderate, LO= Low Yüklə 3,88 Mb. Dostları ilə paylaş:
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