Ton Snelder, Maurice Duncan, Marty Bonnett

Transcription

1 Waiau River mid-range flows: the importance of flow variability ab Doug Booker, Don Jellyman, Ton Snelder, Maurice Duncan, Marty Bonnett

2 Contents 1. Our brief from ECan 2. Analysis of 6 scenarios on: i. Hydrology ii. Periphyton flushing iii. Bed shear stress iv. Fish movements 3. Conclusions

3 2) Our brief from ECan Environment Canterbury (ECan) will define management of flows in the Waiau River minimum flow requirements already defined mid-range flows (i.e. between the mean annual low flow and the mean annual flood flow) will be affected. ECan requires assessment of the potential effects of the changes to mid-range flows 6 flow allocation scenarios

4 Marble Point Power canal return Main take point 2D model location Several small takes Main take

5 i) Hydrology Six flow management scenarios for Waiau River. A minimum flow of 2 m 3 s -1 applies to all scenarios. A-block Gap? B-block Share B-block? :1 sharing

6 Di scharge (m3/s ) : a typical year 1987 Natural Scenario Scenario6_A2B45share Scenario5_A2G2B45 Scenario4_A2G2B15 Scenario3_A65 Scenario2_A35 Scenario1_A Day of year FRE3 FRE2

7 1983: a wet year 1983 Di ischarge (m3/s s) Natural Scenario Scenario6_A2B45share Scenario5_A2G2B45 Scenario4_A2G2B15 Scenario3_A65 Scenario2_A35 Scenario1_A Day of year

8 Di scharge (m3/s ) : a dry yyear 1973 Natural Scenario Scenario6_A2B45share Scenario5_A2G2B45 Scenario4_A2G2B15 Scenario3_A65 Scenario2_A35 Scenario1_A Day of year

9 25: a very dry year 25 D ischarge (m3/ /s) Natural Scenario Scenario6_A2B45share Scenario5_A2G2B45 Scenario4_A2G2B15 Scenario3_A65 Scenario2_A35 Scenario1_A Day of year

10 Flow duration curves Natural Scenario Scenario4_A2G2B15 Scenario5_A2G2B45 Scenario6_A2B45share 1^3. 1^2.5 1^2. 3/s) Discharge (m 1^1.5 1^3. Scenario1_A2 Scenario2_A35 Scenario3_A65 1^2.5 1^2. 1^ Percent of time that flow is not exceeded

11 Days of accrual Scenario4_A2G2B15 Scenario5_A2G2B45 Scenario6_A2B45share Numbe er of events Natural Scenario1_A2 Scenario2_A35 Scenario3_A Number of days since (Natural) FRE3 Distribution of number of days of accrual between FRE3 (3 times the natural median)

12 Ma at ii) Periphyton Aims: Gree n fila Cyanob bacteria To predict the effect of the flow changes on periphyton (mixture of algae, cyanobacteria, heterotrophic microbes, and detritus). Relate the changes to: Maximum Chl a 12 mg/m 2 NRRP objectives for trophic state for alpine Cover (filaments) < 2% (lower) rivers Cover (filaments + Mats) < 3% Didymo

13 Waiau River Periphyton Data SHI Waiau (86 occasions since 24, visual cover) National River Water Quality Network (NRWQN) monthly samples since 1989 of: Conductivity, Nutrient species Temperature, Clarity Periphyton (visual assessment) Continuous record of discharge Candidate NRWQN sites analogous to the Waiau River: Hurunui State Highway 1 Waimakariri River at Gorge

14 Probability of exceeding guideline conditional on Da (2 and 3 times median). Summer Winter CH2 (1,45] Proportion of (mats + fils) > 3% (5) (2) (4) (4) (7) (17) (26) ^2. (5,1] (4) (1) (8) (8).25 (8).12 (31).13 Co over (Mats + Fils) 1^1.5 1^1. Days since FRE3 3 (3,5] (2,3] (1,2] (7) (2) (2) (4) () (8) (1) (12) (7) (3) (13) (18) ^.5 (5,1] (18) (6) 1^. (-1,5] (32) 1^. 1^.5 1^1. 1^1.5 1^2. 1^2.5 Number of days since FRE Natural Scenario Scenario6_A2B45share (-1,5] (5,1] (1,2] (2,3] (3,5] (5,1] (1,45] Days since FRE2

15 Overall probabilities and change in probabilities Probability of exceeding 2% cover by filaments Change in probability of exceeding guideline Natural 2.1 Scenario1_A Scenario2_A Scenario3_A Scenario4_A2G2B Scenario5_A2G2B Scenario6_A2B45share Probability of exceeding 12mg/m2 Biomass Guideline Change in probability of exceeding guideline Natural.5 Scenario1_A Scenario2_A Scenario3_A Scenario4_A2G2B Scenario5_A2G2B Scenario6_A2B45share.9 19

16 iii) Bed stress analysis The objective of the bed stress analysis was to find a physical reason for the results of the periphyton analysis. Based on 2D hydrodynamic modelling using the Mouse Point model as was used to assess flow vs instream habitat requirements.

17 Flushing at median flow

18 Flushing of the median flow bed at FRE2

19 Proportion of the median flow bed flushed 1 9 of the bed moved (% %) Surface flushing Pr roportion FRE2 FRE3 Deep flushing Discharge (m3/s)

20 Bed movement summary The periphyton analysis showed that flows of FR2 to FRE3 were required to remove periphyton. The bed movement study shows that at FRE2 and FRE3 substantial parts of the bed, especially the main braids, are being at least surface flushed.

21 vi) Fish migration & dependence on mid-range flows 18 species of freshwater fish have been recorded from the Waiau River catchment. 13 of these are migratory species (ie part of the life cycle is spent in the sea, part in the river). Of these, 4 species migrate only a little way upstream from the sea (inanga, 2 species of smelt, mullet), and their migration unlikely to be affected.

22 Species of fish recorded from the Waiau catchment Migratory Approx. range in Waiau Common name Distance inland (km) Elevation (m) Bluegilled bully * Brown trout Chinook salmon Common bully -8-4 Common smelt -2-4 Inanga -5-2 Koaro Lamprey * Longfin eel Shortfin eel -1-5 Stokells smelt -5-2 Torrentfish Yelloweyed mullet -5-2 Non-migratory Alpine galaxias Canterbury galaxias Goldfish na na Rudd na na Upland bully -16-9

23 Progressive upstream migration For some species (eg bullies, torrentfish, longfin eels) juveniles migrate from the sea and migrate upstream over a number of years (colonisation) Rapid upstream migrants Species such as koaro (one of the whitebait species) and adult salmon make a rapid upstream migration from the sea to the headwaters. The river is more highway than habitat.

24 Torrentfish Bluegill bully

25 Migration Calendar Longfin eel glass eel from sea elver gradual upstream adult downstream Shortfin eel glass eel from sea elver gradual upstream adult downstream Koaro whitebait from sea post-whitebait upstream larvae downstream Lamprey adult upstream ammocete gradual downstream macropthalmia out to sea Torrentfish juvenile from sea growing adult gradual upstream larvae downstream Bluegill bully juvenile from sea growing adult gradual upstream larvae downstream Common bully juvenile from sea growing adult gradual upstream larvae downstream Chinook salmon adult upstream juvenile downstream Brown trout adult upstream juvenile downstream Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

26 Key species longfin eel and chinook salmon Both species are high value. Salmon = recreational importance. Eels = intrinsic, customary and commercial importance Both species are obligatory migrants (i.e. they must migrate to carry out their life histories) Both species migrate extensively up and down the river Adults of both species are relatively large and will require the maximum depth of any of the fish species recorded from the catchment They represent both a slow and rapid migratory species

27 eels Spring Summer Autumn Winter Headwaters km m km m Mouse point 7 23 Waiau Spotswood 13 3 River mouth

28 Chinook salmon Spring Summer Autumn Winter Headwaters km m kmm Mouse point 7 23 Waiau Spotswood 13 3 River mouth -

29 Dry rge (m3/s) Dischar Longfin eel juvenile (up) adult (down) Scenario6_A2B45share Scenario5_A2G2B45 Scenario4_A2G2B15 Scenario3 o3_ A65 Scenario2_A35 Scenario1_A Day of year Salmon juvenile (down) adult (up)

30 Wet Discha arge (m3/s) Longfin eel juvenile (up) adult (down) Scenario6_A2B45share Scenario5_A2G2B45 Scenario4_A2G2B15 Scenario3_A65 Scenario2_A35 Scenario1_A Day of year S Salmon juvenile (down) adult (up)

31 For migrating eels and salmon, the key flow- related features to enable migrations are; the availability of sufficient depth for passage (summer) the frequency and size of freshes and floods (summer) the duration of low flows (the amount of time ( between successive freshes and floods) - summer

32 Scenario6_A2B45share Spring Summer Autumn Winter Number of freshes (events exceeding the median flow) during each season for each scenario Scenario3_A65 Scenario4_A2G2B15 Scenario5_A2G2B45 Density Natural Scenario1_A2 Scenario2_A Number of events exceeding natural median

33 .6 Scenario6_A2B45share Spring Summer Autumn Winter Maximum number of days between events exceeding the median flow, by season and scenario Scenario3_A65 Scenario4_A2G2B15 Scenario5_A2G2B45 Density Natural Scenario1_A2 Scenario2_A Maximum duration between median flow events for each year

34 Summary: Fish migrations (juvenile eels and adult salmon) and summer flow variability Scenario preferences Number of freshes: Natural,1,2,4,(3,5,6) Durationoflowflows:Natural124(356) of flows: Natural,1,2,4,(3,5,6)

35 Summary Mid-range flows are important. Reducing number of FRE2 and FRE3 (increases duration between these events), is likely to decrease frequency of sediment movement increase frequency of breaches of the NRRP periphyton objectives decrease triggers for fish migrations

36 Extras

37 1) Why mid-range flow are important, t biological i l examples Flow (cumecs s) Bank submergence, spawning Gestation, exposed to air Bank submergence, hatching Time (months) 1. Maintenance of spatial & temporal heterogeneity for aquatic communities 2. Stability (or lack of) primary production (algal growth, invert grazing) 3. Salmon migration bar-opening floods, recessions for migration 4. Reproduction in native fish (koaro, banded kokopu, short-jawed kokopu)

38 The probability of high flows for the abstraction scenarios. The lower the probability the lower the sediment transport. 1.E+ Flow (log Q (m3/s) E-1 FRE3 1.E-2 robability Log P 1.E-3 1.E-4 1.E-5 Umodified 1_A2 2_A35 3_A65 4_A2_gap2_B15 5_A2_gap2_B35 6_A2_B45share 1.E-6

39 Numbe er of years floods/y 5-8 floods/y 9-12 floods/y floods/y The effect of abstraction on vegetation encroachment 5 Unmodified s1_a2 s2-a35 s3_a65 Abstraction scenario The more often there are years with low numbers of floods and the more often there are long periods with out floods the greater the likelihood of vegetation encroachment. Number of i nter-flood peri ods months 3-6 months 6-9 months >9 months Unmodified Scenario1_A2 Scenario2-A35 Scenario3_A65 Abstraction scenario

40 .25 Scenario6_A2B45share Spring Summer Autumn Winter Maximum number of days between events exceeding two times the median flow, by season by scenario Scenario3_A65 Scenario4_A2G2B15 Scenario5_A2G2B ty Densit Natural Scenario1_A2 Scenario2_A Maximum duration between 2*median flow events for each year

41 Proportion of the minimum flow bed 1 flushed 9 Proportion of the be ed in motio on (%) FRE2 FRE3 Surface flushing Deep Flushing Discharge (m3/s)

42 Bed movement criteria Criteria taken from a Nth American study of a river with a similar flow to the Waiau The model calculates the bed shear stress to move: fine sediment and periphyton filaments and mats = surface flushing D 5 sediment = bed movement = deep flushing. We calculated the proportion p of the median and minimum flow beds that were surface and deep flushed at a range of flows.

43 torrentfish Spring Summer Autumn Winter Headwaters km m kmm Mouse point 7 23 Waiau Spotswood River mouth

44 koaro Spring Summer Autumn Winter Headwaters km m kmm Mouse point 7 23 Waiau Spotswood 13 3 River mouth -

45 Number of adult brown trout entering Glenariffe Stream trap from the Rakaia River

46 Increased flow versus base flow x x 2 x 2-3 (4) x 5 x 1 >1 Adult lamprey + - Glass eels + (Waikato) (Waikato) Elvers + Silver eels + Giant kokopu + Adult brown trout Rainbow/brown + trout adults Salmon adults + + Salmon fry + +

47 Normal Disc charge (m3/s) Longfin eel juvenile (up) adult (down) Scenario6_A2B45share Scenario5_A2G2B45 Scenario4_A2G2B15 Scenario3_A65 Scenario2_A35 Scenario1_A Day of year S Salmon juvenile (down) adult (up)

48 Seasonal flow duration curves Natural Scenario 1^3. Spring Scenario1_A2 Spring Scenario2_A35 Spring Scenario3_A65 Spring Scenario4_A2G2B15 Spring Spring Scenario5_A2G2B45Scenario6_A2B45share 1^2.5 1^2. 1^1.5 1^3. Summer Summer Summer Summer Summer Summer Scenario1_A2 Scenario2_A35 Scenario3_A65 Scenario4_A2G2B15 Scenario5_A2G2B45 Scenario6_A2B45share 1^2.5 1^2. 3/s) Discharge (m 1^ ^3. 1^2.5 Autumn Scenario1_A2 Autumn Scenario2_A35 Autumn Scenario3_A65 Autumn Scenario4_A2G2B15 Autumn Autumn Scenario5_A2G2B45Scenario6_A2B45share 1^2. 1^1.5 1^3. Winter Scenario1_A2 Winter Scenario2_A35 Winter Scenario3_A65 Winter Scenario4_A2G2B15 Winter Winter Scenario5_A2G2B45Scenario6_A2B45share 1^2.5 1^2. 1^ Percent of time that flow is not exceeded