NEPAL Fish passages in a hilly Country by
Halvard Kaasa
Fish ladders i Nepal • • • •
Little knowledge about the existing fish ladders Less than 10 fish ladders/fish passages Many of them are said not to be working Only one fish passage where Scientific research is conducted to examine the effect of the fish ladder/fish passage • Khimti khola HP (Himal power ltd.)has carried out survey describing functionality of the upstream migration and downstream tunnel entrapment frequency.
Fish ladders in Nepal Some examples Locality
Name
Type of ladder
Height
Nr of steps
Khimti khola
Palati fish weir
N
16 m
No steps
Andhi khola
Gulyang
P
6.5 m
Jimruk
Khaira
P
3.5 M
Kohsi Barrage Khudi khola
Kaligandaki
Type of fish ladder Naturelike: N Pool type: P Vertical slot: V Denil: D
Khudi Bazar
P N
Downstream pipe
Working on high flow Yes
Working on low flow Yes
Based on scientific resaearch
Based on scientific resaearch
14
200 l/s
Yes *
No *
8
200 l/s
Yes *
Yes * No * Yes *
Yes ? *
5M
No Steps
140 l/S
No * Yes *
18 M
pipe
4 m3/S
Yes ? *
Trap and transport: T&T Sluiceway: S Presur chamber fish way: PC
*Evaluation based on Nepalese experience
Flow through fish ladder Min 0,5m3/s
Fish species Asala- Schizothorax richardsonii Katle- Neolissochilus hexagonolepis Titae- Psilorhynchus pseudecheneis Sahar-Tor putitora
Fish species
Asala Titi Katle Asala, Sahar, Gurdi, Katle Asala, Katle, Bam
Asala, Katle
Downstream migration only
Gurdi-Labedo dero Bam-Anguilla bengaliensis
Jimruk Fish ladder
Koshi fish ladder Not working as expected
Kaligandaki HP
Kaligandaki downstream sluice pipe
Trisuli , old HP in lower pĂĽart of the river
Andhi khola fish ladder
Photo BPC
Khimti khola fish passage
Ecological corridors in regulated rivers To maintain ecological corridors for fish by building fish ladders so as part of the fish population might pas the technical installations call for a safe downstream passage for this part of the population. Elsewhere an upstream passage with high downstream migrant mortality might be a start of a death spiral of the migrating population.
.
Is there Need for a fish ladder or a fish passage? Do a fish ladder ad ecological value?
Baseline A year cycle
Environmental parameters • • • • • • • • • • •
Flow Velocity Temperature Light conditions Biodiversity Waterquality Sediment load Fish migtion Invertebrates etc. Sum of effects
Ecodynamic baseline quality
When a fish ladder or a fish passage is a recommended solution the following parameters are crucial: • Target fish species • Localization • Hydraulics in the ladder
Katle
Asala
Titae
Hydraulics and fish Hydraulic properties adapted to the target species
Khimti khola, Palati intake site and fish passage
Waterfall in Khimti khola that asala pass upstream
Fish migration across the weir - results • Use of fish trap from 8th Jan. – 14th May • Total 49 days (24 hours) • Total catch 33 Asala and 17 Titae
Fish entrapment in the tunnel • driftnet 2006/2007 and 2008 (mature fish)
KHIMTI • • • • • • •
Fish population is vigorous and in stabile condition Sign of change in migration Sign of change in biomass production 3000 mature fish entrapped in the tunnel a year Fish can pass the weir with flow of 0,5m3/s Mitigation by fish ponds by use of fry from the river Mitigation by strengthening nutrient chain in the river
Monthly cach (number of fish) inlet 2006 12000
Fish entrapment in the tunnel
Number of fish
10000
Tailrace Inlet
8000 6000 4000 2000 0 Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sept
Oct
Nov
Dec
Month
Monthly catch (number of fish) inlet / tailrace 2007 12000 Tailrace Inlet
Number of fish
10000 8000 6000 4000 2000
Total monthly calculated number of fish in the inlet of the tunnel at Palati and in tailrace downstream the power station from July 2006 to July 2008. * indicates no sampling
0 Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Month
Monthly catch (number of fish) inlet / tailrace 2008 12000
Tailrace Inlet
10000
Number of fish
•
8000 6000 4000 2000
*
0 Jan
Feb
Mar
Apr
* Ma
* Jun
Jul
Month
Aug
Sep
Oct
Nov
Dec
Khimti HP, registration of fish that has passed the turbines
Fish passage- Fish ladder • Is it need for a fish passage? • Baseline knowledge • Eco dynamic conditions need a fish ladder • Select suitable transect that give space for the fish ladder or the fish passage • Select design of fish ladder based on hydraulic conditions adapted to the target species and the local conditions. • Select entrance to the fish ladder adapted to the target fish species
• Select exit from fish ladder to upstream of dam or weir as far a way from the HP-inntake site as possible
Thank you for your attention