Fish Passage Options for Upper Trisuli-1 HEP, Nepal : Perspectives and Challenges
Upper Trishuli-1 (216 MW) Project Location 2
UPPER SANJEN (14.8MW) RASUWAGADHI (111MW)
(India + Nepal)
(China)
SANJEN (42.8MW) (India + Nepal)
Rasuwa Bhotekoshi (120 MW)
CHILIME (22.1MW)
60 MW UT-3B (37 MW Planned)
Project Summary Details Name:
Description •
Nepal Upper Trishuli-1 HEP( 216 MW)
•
NWEDC (Nepal Water and Energy Development Company)
•
216MW (72MW Turbine X 3units)
•
Concrete Dam(H=32m), Headrace Tunnel(D=6.5m, L=9.7km)
•
Powerhouse Cavern (W18.7m*H43.9m*L145.4m)
•
Surge Tank, Access road, Diversion works
•
Camp Office and Operating Facility
•
Generators and Transformers
•
1,533.1 GWh (Estimation of Monthly Discharge)
Type:
•
Run of River
Estimated Project Cost
•
USD 580 mil. (EPC : 370 mil.)
Model:
•
BOOT(Build-Own-Operate-Transfer)
River:
•
Rasuwa Trishuli River
Distance:
•
70 KM from Kathmandu
•
O&M : KOSEP
•
EPC : DKJV
Project Company:
Project details:
Gross Energy:
Contractor:
PROJECT LOCATION
Requirements for fish passages : Legal and compliance Compliance with Nepal National Requirements and IFC’s Performance Standards 6 : Bio-diversity Conservation and Sustainable Management of Living Resources Eflow assessment report (2014): the weir is likely to create impassible barrier for upstream migration…. Committed to Projects’ EIA/EMP approved by Government of Nepal Section 5B of Nepal Aquatic Animal Protection Act of 1961, and its first amendment (1997) mandates of fish ladder while developing dam in HEP
Hypothesis- Barrier effect, migration and habitat
Diversion Area • Approximately 12 km long river stretch
Fish Diversity in Trisuli River Fish Diversity Monthly Variation Trends in the Monitored
Fish Diversity across Monitoring Months,
Trishuli River Stretch
2014/2015 Fish Diversity
Number of Species
5 4 3
Schizothorax richardsoni Schitura savona Psedecheneis
2
sulcatus Euchiloglanis
1
hodgarti Noemacheilus
0
Monitoring Months
Beavani Onchorhyncus mykiss
Monitoring Months

Schizothorax richardsoni is the dominant fish species confirmed by - 99% of the total fish catch by caste net - 100% of the fish catch by gill net
Fish Diversity in Trisuli River
Fish Diversity in Trisuli River
Pseudecheneis sulcata
Nemacheilus rupicola
Garra annandalei
Glyptosternum blythi
Snow Trout- habitat characteristics Prefer to live in clear and fast flowing rivers within the temperature of 8 to 22°C Prefer rapids, pools and riffle types of habitat Spawning characteristics: Mature Asala spawn naturally when they reach 18~24 cm length Age at spawning: 2 years Ideal spawning conditions (at tributaries): I) Clear water II) Gravelly/Stony grounds or on fine pebbles at 1~3 m depth III) Gravel size of 50~80 mm IV) Water current (2.8~4.0 m/s) V) pH 7.5 VI) Dissolved oxygen concentrations of 10~15 mg/L Spawn in 2 distinct periods: I) Start of monsoon season (Mar-May), coinciding with upstream migration II) End of monsoon season (Sep-Nov), coinciding with downstream migration (Source : EIA/CIA, UT-1)
Fish species and ecology: findings Snow Trout (Schizothorax richardsonii)- form local population that might be the resident part of gene pool A part of population has adapted to mid-range migratory behavior as part of life strategy security system for dissemination of gene and offspring A local resident population might be very well be able to survive WITHOUT supply of genes and individuals from migrating part of fish population An important part of population survival strategy seems to be downstream spreading of offspring from the spawning areas Upper part of main river in normal flow condition is probably a low productive and marginal environment : low temperature, high turbidity and turbulence in nature Dewater zone in winter season might favor fish population : temperature rise from stronger influence from tributaries, reduction of sediment load, increase allochthonous organic matter
5 Design Fish Ladders in HEPs of Nepal (Pool and Weir) : Jhimruk & Adhikhola
5 Design
Fish Passage Options for Upper Trisuli-1 • Hydraulic condition suitable for Snow Trout as a basis for fish ladder design • By using design criteria adapted to swimming and jumping ability, and taken into local temperature into account different types of fish ladders at UT-1 dam is possible • Daeliem-Kyeryong –Contractor recommend Trap and Transport (upstream migration corridor & new spawning ground • Design of the inlet arrangement to the trap or fish ladder is vital for the function of the selected method
5 Design
Fish Passage Options for Upper Trisuli-1
Pool Type
Trap and Transport
Pros
Low manual effort
No waste of water No initial construction cost
Cons
Continuous water releasing during power plant operation High construction cost initially
High manual effort (standby arrangement
• Due to the localization of dam in rural area, it might be appropriate to use fish ladder solution that involve low input of manual work or tech nical handling of the fish. • Different variations in pool type fish ladder with rectangular notches for overflowing water with submersed orifices, and vertical slot fish la dder
7
Dam Site- Fish Ladder Space Available in Left Bank
5 What Next Under Consideration Design • Excess water flow over the dam as close to the left bank as possible without conflicting fish ladder to be located at left bank • Overflow gates should have capacity to let main flow passing during monsoon • Radial gate should be used under very high floods, and should be located in the middle of dam • Spillway should be ogee formed construction with a smooth concrete surface and with no obstacles no steeper than 1:0.8 • Create a deep pool with volume and depth making entrance for fish making sure less harmful (injury or kill) to fish • Which types of fish passage systems will be for UT-1 is under discussion : fish ladder with pool, or nature like fish path in downstream with trap and lift
Cumulative impact :Trishuli River Watershed~1133 MW In Operation (6%) 6 Projects: 71.75 MW
Under Construction 12 Projects: 545.9 MW
Under Survey License 21 Projects: 495.67 MW
Downstream Hydroproject’ Dam UT-3A