Consigned to the deep: requiem or recovery of VR2W receivers in a freshwater river gorge after a 1:2-3 3 year ARI flood

Transcription

1 Consigned to the deep: requiem or recovery of VR2W receivers in a freshwater river gorge after a 1:2-3 3 year ARI flood 1 Ivars Reinfelds, 2,3 Chris Walsh and 1 Tim Haeusler 1 Department of Water and Energy, Water Utilities and Science Division, PO Box 53,Wollongong, NSW 2500, Australia 2 Department of Primary Industries, Cronulla Fisheries Research Centre of Excellence, PO Box 21, Cronulla, NSW 2230, Australia. 3 School of Biological Sciences, University of Wollongong, Northfields Avenue, Wollongong, NSW 2533, Australia.

2 Aims of presentation F Outline rationale to monitoring of migrations and movements of Australian bass and estuary perch in the Shoalhaven River below Tallowa Dam F Outline range of supporting data available to interpret fish migrations, movements, behaviour and cues F Outline receiver deployment and anchoring techniques in a freshwater river gorge and their success/failure in a major flood F Discuss range testing results for VR13-1L transmitters in a semi-alluvial freshwater river gorge F Discuss lessons learned so far and questions we hope to answer

3 Discharge (Ml d -1 ) m. Tallowa Dam inflow Tallowa Dam outflow 2 m. 10 1/01/2005 1/04/ /06/ /09/ /12/2005 Hydrological effects of Tallowa Dam F Catchment area 5750 km 2 operational capacity 35 GL F Drought reserve for Sydney s water supply F Tallowa Dam has a low operating capacity relative to inflows frequent spills during wet years F During dry years (eg. 2005) small events <1.1 year flood can be fully captured, large floods minimally impacted F Environmental flow studies primarily focussed on effects of flatlining of low flows F Dam effects primarily occur within m of low flow water level F Minimum depths and max velocities for fish passage a key consideration

4 Shoalhaven River freshwater section F 21 major riffles from dam to tidal limit distance 25 km F Riffles vary from m length, separated by pools about 830 m in length F Wide-shallow, steep-turbulent riffles considered most problematic to fish passage F Wilderness area - canoe or small plastic boat access only

5 Riffle 6 Nov ML/d Examples of wide-shallow riffles Riffle 6 Nov 130 ML/d Riffle 7 Nov 130 ML/d F Wide shallow riffles are thought to be depth limiting for fish passagep F Exhausted fish observed trapped within wide-shallow riffles

6 Examples of steep-turbulent turbulent riffles Steep-turbulent turbulent riffles are thought to be velocity limiting for fish passage under low flow conditions Riffle 2 - April 2005 Riffle 10 - April 2005 Approximately 1 m headloss over 20 m, slope ~0.05 Velocities >1.8 ms - 1 over distances ~6-10 m or greater considered problematic for adult Australian bass

7 Supporting data for interpretation of fish movements F Detailed airborne laser, topographic and bathymetric survey data for DTM s full river and estuary coverage F Two gauging stations (flow and temperature) F High-resolution aerial photos and SPOT5 imagery F One and two dimensional hydraulic models (flow velocities and depths) F Salinity meters and hydrodynamic salinity model (estuary)

8 Receiver deployment: consigned to the deep F Freshwater receiver deployment locations pre-determined in GIS from bathymetric, hydraulic model and aerial photo data F Typically one receiver per pool (the two largest pools have two receivers each) F Deployment site located and marked in field with float F 80L cordura anchor bag filled with cobbles collected on-site, estimated weight ~100 kg F Ropes measured so that buoy suspending receiver was ~80 cm below water surface F Plan was to snorkel and unclip receivers for data downloads

9 Shoalhaven River VR2W receiver array F Deployment of 21 freshwater receivers, 29+ estuarine receivers. Largest FW-estuarine array in SE Australia? F Opportunity for detailed comparisons/contrasts between movement, migrations, behaviour and cues for Australian bass and estuary perch

10 Distance across channel (m) Legend WS 1.1 year ARI WS 4000 ML/d WS 1500 ML/d WS 500 ML/d WS 130 ML/d Ground Bank Sta Instantaneous maximum discharge (ML d -1 ) approx. 8 m rise Peak flow 1505 m 3 s /05/2007 1/06/ /06/ /06/ /07/ /07/2007 Legend 35 Floodplain inundation, widespread stripping of riparian vegetation 20 year ARI flood WS 20 year ARI Bench reworking, limited stripping of riparian vegetation Bedload transport, inundation of high level benches Bedload transport, reworking of gravel bars Macrophyte scour, inundation of low level benches 1.5 year ARI flood Macrophyte scour, pool fines & sand flushing Pool fines flushing 130 ML/d current environmental flow 1.1 year ARI flood 4000 ML/d 5 year ARI flood 2 year ARI flood 10 year ARI flood Low benches Elevation AHD (m) High bench Floodplain Pool fines flushing Riffle fines flushing Pool mixing and de-stratification Fish passage, low flow habitat 130 ML/d current environmental flow year ARI flood 4000 ML/d 1500 ML/d 500 ML/d Instantaneous maximum discharge (m 3 s -1 ) WS 10 year ARI WS 5 year ARI WS 2 year ARI WS 1.5 year ARI WS 1.1 year ARI WS 4000 ML/d WS 1500 ML/d WS 500 ML/d WS 130 ML/d Ground Bank Sta June 2007 flood F Flood on 15 June 2007 attained peak flow rate of 1505 m 3 s -1 six weeks after receivers deployed F Event rose ~8 m above low flow water level F Estimated recurrence interval 1 in 2-3 years F Peak velocities typically ms -1 at receiver deployment locations F Flood effective at transporting bedload cobbles/gravel, macrophyte scour F Bankfull floodplain approx 18 m above low flow water level!

11 Impact of June 07 flood on project F Stimulated a good breeding event for bass (and perch?) in the estuary F 2 out of 20 receivers deployed before flood irretrievably lost F Entrainment of large woody debris caused receiver loss F 8 out of 20 anchor bags rolled 1-3 times, 4 bags buried under bedload sediment F Floats, receivers etc dragged 1-3 m deeper due to bag rollover, problematic for receiver/data retrieval F Receiver attachment system extended with wire rope easier data downloads, lift into canoe

12 Range testing method F Computer set to GPS time, receivers set to computer time F Range testing undertaken after 2-3 year ARI flood event F Trolling of V13-1L transmitter with ~5 s transmission interval alongside canoe F Garmin ETrex Vista handheld GPS used to log track at maximum resolution (10 m spacing between track points) F GPS time stamp related to VR2W detection time stamp in Arcview GIS to determine start finish of detection range

13 230 m 165 m 255 m 125 m Range testing results F Upstream-downstream detection distances range from m (n=3), average 190 m F Detection range influenced by pool geometry, bathymetry and flow rate F Receivers capable of around the corner and possibly some over riffle detection (at elevated flow) F Each receiver covers ~40% of the average pool length in the Shoalhaven River (average pool 830 m long)

14 What we hope to learn Stage at Grassy Gully (m) /11/07 12:00 11/12/07 0:00 11/12/07 12:00 11/13/07 0:00 11/13/07 12:00 11/14/07 0:00 11/14/07 12:00 11/15/07 0:00 11/15/07 12:00 11/16/07 0:00 11/16/07 12:00 F Detailed comparisons/contrasts between movement, migrations, behaviour, spawning areas, cues and environmental factors influencing Australian bass and estuary perch (Chris Walsh s PhD) 11/17/07 0:00 F 17 bass and 14 estuary perch with V13-1L tags, more to come F First fish released Sep 2007 F Approx 200,000 detections in estuarine array F First bass reached upstream limit of estuary 8 days after release (40 km swim) F Only 1 bass had moved into freshwater by Nov 2 despite plenty of time to do so F Adult bass post-spawning upstream migrations - are freshes important or will fish migrate under regulated baseflow release? F Small spill from Nov requisite cue for stimulating upstream movements?

15 Lessons learned to date Lessons learned to date F Anchoring system resistant to floods probably to ~5 years ARI F 2-3 year ARI flood caused loss of 10% of deployed receivers F Sub-surface moorings problematic due to bag rollover F Large woody debris main cause for receiver loss F Wire rope (5 mm) more resistant to abrasion than nylon rope and hopefully vandal proof F Departmental insurance covered loss of two receivers F Factor receiver loss and unexpected problems into budget