Determining GEP in HMWB - The example of the Aura water course

Transkript

1 Determining GEP in HMWB - The example of the Aura water course Odd Terje Sandlund, Arne J. Jensen, Anders G. Finstad

2 Determining GEP in HMWB - The example of the Aura water course Assessing procedures to define Good Ecological Potential (GEP) in HMWB Applied on water bodies affected by the Aura hydropower development Three major developments: 1953 (Aura) 1962 (Takrenna) 1975 (Grytten)

3 The road to ecological potential Tentatively identified as HMWB Final classification as HMWB Establish EP

4 If properly documented, the process is transparent and may be checked by all stakeholders (1) Identifisering av vannforekomst? Nei (3) Grovsiling Er det hydromorfologiske endringer? Ja (4) Beskriv endringer i hydromorfologi Nei (5) Er det sannsynlig at vannforekomsten ikke vil oppnå god økologisks tilstand som følge av hydromorfologiske endringer? Ja Miljømål er god økologisk tilstand: ikke SMVF Nei (6) Har vannforekomsten vesentlig endret karakter som følge av fysiske endringer med årsak i menneskelig aktivitet? Ja Foreløpig klassifisert som SMVF

5 Alternative approaches to GEP Alle mulige tiltak som ikke er vesentlig til hinder for bruk (i) Original approach Via MEP to GEP Definer MØP som verdi av BKE etter at alle tiltak er gjennomført Alle mulige tiltak som ikke er vesentlig til hinder for bruk (ii) Alternative approach MEP as a sideline Definer MØP som verdi av BKE etter at alle tiltak er gjennomført Identifiser tiltak som er nødvendig for å oppnå GØP Definer GØP som minimale avvik fra MØP Ekskluder tiltak som gir minimale økologiske forbedringer Definer GØP som verdi av BKE etter at alle inkluderte tiltak er gjennomført GEP defined as the result of all relevant measures MEP defined as the result of all imaginable measures

6 Water bodies assessed Eresfjord The river Eira The lake Eikesdalsvatnet The river Aura The reservoir Aursjømagasinet The reservoir Reinsvatnet The river Litjdalselva

7 Example: Aura

8 Down with sheep, up with salmon! (Jensen & Johnsen 2007, NINA Rapport 275)

9 1-6: Preliminary classification as HMWB 1. Type of water body River 2. Artificial WB? No 3. Hydromorphological changes? Yes 4. Changes in hydromorphology / ecology Major portion of the catchment area transferred to neighbouring watersheds Sign. reduced water flow. River sections periodically dry. Pop. of resident brown trout significantly reduced. Pop. of salmon and sea trout nearly lost 5. May WB reach good ecological status (GES) without mitigating actions? No 6. Are hydromorphological changes due to human interventions? Yes

10 7-9: Final classification as HMWB 7. Mitigation required to achieve GES GES characteristics Water flow securing continuous surface water Migration and spawning opportunities for anadromous fish similar to pre HP-development Aquatic vegetation and fauna similar to natural river Self-sustaining pop. of anadromous and resident fish on the whole river stretch Mitigation Release of water from reservoir Does necessary mitigation negatively affect other use? Yes, significantly reduced HP production 8. May other use be replaced by alternative activities? No 9. Final classification as HMWB Yes

11 Required measures for MEP and GEP With the knowledge about Aura, it is relatively simple to come up with relevant measures Regarding other water bodies (the fjord, the river Litledalselva) it is simply guesswork

12 The salmon year : 1. Downstream migration of smolts (in this case: May) 2. Upstream migration of spawners (from mid-july through August) 3. The rest of the year (Jensen & Johnsen 2007, NINA Rapport 275)

13 11: Establishing GEP Required measures to achieve GEP a) Minimum flow without physical measures Minimum flow during smolt migration 15 m 3 /sec Minimum flow during upstream migration of salmon and seatrout m 3 /sec Minimum flow 2m 3 /s during the rest of the year b) Minimum flow without physical measures Excavation of deep river channel in parts of river upstream of Litlevatnet Fish ladder downstream of Litlevatnet Minimum flow during smolt migration 15 m 3 /sec Minimum flow during upstream migration of salmon and seatrout m 3 /sec Minimum flow 1 m 3 /s during the rest of the year

14 Required water flow without physical measures 40 Vannføring (m 3 /s) jan mai sep jan (Jensen & Johnsen 2007, NINA Rapport 275)

15 Cost benefit estimates Hydropower production (monetary value) Climate value of HP production to replace fossil fuel energy vs. The value of salmon fishing (recreational) But: Every litre of minimum flow water may be utilized if a new hydropower plant is constructed at the top of Aura salmon stretch 650 m drop from Aursjøen reservoir This was not included in our analysis

16 Mitigation measures in the HMWBs Eira Stocking of salmon smolts, habitat improvements to increase shelter, restoration of tribuataries (sea trout), measures in Aura Reinsvatnet Alternative 1: Reduce accessible spawning areas Alternative 2: Stock reduction by fine meshed gill net fishing Litjdalselva Habitat improvements, fish barrier in front of power plant discharge channel Aursjømagasinet Stocking programme, habitat improvements in spawning streams, highest possible water level during trout spawning period, weir to keep Gautsjøen above 853,0 m

17 Conclusions and reflections Standardised and stepwise process allows for transparency and public control In this case: GEP ~ MEP No practical difference between the two alternative approaches to establish GEP GEP based on mitigation packages appears well argued Salmonid stock status is often the only available quantitative quality element but are salmonids good indicators on ecological status or potential?

18 Thank you for your attention!