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CIS ECOSTAT - HYDROMORPHOLGY WORKSHOP 12th and 13th June 2012 - Brussels. Hydropeaking and minimum flow : the French approach. P. Baran. Pôle Ecohydraulique. French context of water storage. Total amount of water per year in stream : 200 billion m3

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Hydropeaking and minimum flow the french approach p baran

CIS ECOSTAT - HYDROMORPHOLGY WORKSHOP

12th and 13th June 2012 - Brussels

Hydropeaking and minimum flow : the French approach.P. Baran

Pôle Ecohydraulique


French context of water storage
French context of water storage

  • Total amount of water per year in stream : 200 billion m3

  • In 2009, 33,4 billion m3 in total collected :

    • 64% for the production of electricity

    • 17% for drinking water

    • 10% for the industry

    •  9% for irrigation

  • The water storage has been developed for :

    • irrigation,

    • hydropower generation

    • drinking water

  • 126 000 samples of water whose 80,000 for agricultural use


French context for hydroelectricity
French context for hydroelectricity

  • Production :

    • Between 60 to 70 TWh for hydroelectricity (550 TWh of total production),

    • 50% of the production by hydropower plants managed by hydropeak with to type of schemes :

      • organized in line (eg: Durance, Dordogne, Truyère).

      • organized with high-head storage (Alpine and Pyrenean mountains)


French approach
French approach

  • Identification and quantification of changes of flow regime with two priorities :

    • Low flow

    • Hydropeaking

  • Mitigation measures to increase low flow value (large scale (2014)) and/or to change locally the hydropeaking management.



Focus on hydropeaking

Principales centrales hydrauliques

Focus on hydropeaking

  • More than 150 hydroelectric schemes managed by hydropeaking in France.

  • ≈ 3000 kms of streams concerned by hydropeaking.


Hydropeaking and minimum flow the french approach p baran

The French approach

  • 1. Identifications of flow modifications induced by hydropeaking

Analysis of flow regime

7


Hydropeaking and minimum flow the french approach p baran

The French approach

  • 2. Identifications of habitat alterations related to the flow modifications induced by hydropeaking

Characterization of fish habitats by hydraulic models and habitat preference curves of species and life-stages

8


Hydropeaking and minimum flow the french approach p baran

The French approach

  • 3. Proposal of mitigation measures and assessment

Approach based on hydraulic models and habitat mapping

9



Method to characterize the hydrological disturbance
Method to characterize the hydrological disturbance

  • Data base : gauging stations

  • Hourly flow analysis

    • Identification of each flow variations

    • Differentiation between the hydropeak and natural variations


Method to characterize the hydrological disturbance1
Method to characterize the hydrological disturbance

  • number of hydropeaks,

  • Each hydropeak is characterized by :

    • base flow,

    • maximum flow,

    • range,

    • rate of change,


Method to characterize the hydrological disturbance2
Method to characterize the hydrological disturbance

  • For each year :

    • Number of hydropeaks

    • Statistical characteristics of :

      • base flow,

      • maximum flow,

      • range,

      • rate of change,

Number of hydropeaks

Rate of change

Base flow

Range


Hydropeaking and minimum flow the french approach p baran

Daily hydropeaks

Hourly hydropeaks

Weekly hydropeaks


Characterization of hydrologic perturbation
Characterization of hydrologic perturbation:

  • Construction underway of an indicator of hydrologic perturbation due to hydropeaking events.

  • Based on discriminant analysis :

  • base flow,

  • maximum flow,

  • range,

  • rate of change,

  • number of hydropeaks


Characterization of hydrologic perturbation1

Saint-Béat - 2006

Characterization of hydrologic perturbation:

  • The index just evaluate the hydrological perturbations and not ecological effects

  • The index allow to analyse the evolution of the perturbation along a stream or between years.

Chaum - 2006

Upstream

Valentine - 2006

Downstream


Global situation in france
Global situation in France:

  • 80 stations were analysed in 50 french streams. 58% of stations with strong alterations of flow regime



Impacts on fish habitat

Two types of impacts on fish habitat depending on morphology of stream.

Impacts on fish habitat

Mountain steep stream : hydraulic conditions during high flow


Impacts on fish habitat1

Effects of hydropeaking management during life-stages of fish

Impacts on fish habitat

Lez river (MD : 1 m3/s)

Hydrologic perturbation very marked, maximum discharge 4 m3/s (≈4 times MD), between 150 and 300 hydropeaks per year.


Impacts on fish habitat2

Two types of impacts on fish habitat depending on morphology of stream.

Impacts on fish habitat

Braided streams :

Hourly variations on wetted perimeter dewatering fish habitats on shallow shoreline areas and trapping fry in disconnected secondary channels


Impacts on fish habitat3
Impacts on fish habitat of stream.

  • Monitoring two streams (MD :107 m3/s; MD : 20 m3/s)

Line of lakes and hydropower plants

Hydrologic perturbation very marked, maximum discharge 35 m3/s (≈1,8 times MD), between 150 and 300 hydropeaks per year.

Hydrologic perturbation marked or very marked, maximum discharge 340 m3/s (≈3.2 times MD), between 100 and 240 hydropeaks per year.


Impacts on fish habitat4
Impacts on fish habitat of stream.

  • Monitoring ecological effecfs of hydropeaks

    • Dewatering of salmonid redds and mortality of eggs (30% of the total redds).

    • Trapping of fry in disconnected secondary channels and mortality (6000 fry/year on 6 kms of stream).

Back to base flow

During a hydropeak


Mitigation measures
Mitigation measures of stream.

  • Two types :

    • Changes on hydropeaking management :

      • Number of hydropeaks during specific biological periods,

      • Base flow, range, maximum flow, rate of change

  • Changes on stream morphology :

    • Connectivity of secondary channels,

    • River banks

    • Topography of gravel bar


Mitigation measures1
Mitigation measures of stream.

  • Base flow increased :

    • from 0.5 m3/s to and 4 m3/s (5-20% of MD) in winter and spring, 1 m3/s the rest of the year

    • From 10 m3/s to 30 m3/s (28% of MD) in winter and spring (15/11-15/06), 10 m3/s the rest of the year.

  • Maximum discharge limited :

    • to 35 m3/s (less than 2 times MD), if possible, in spring (15/03-15/06).

    • to 190 m3/s (less than 2 times MD), if possible, in spring (15/03-15/06).

  • Discharge downramping rate of change limited :

    • to 20 m3/s/h in spring (15/03-15/06).

    • to 30 m3/s/h all year round.

  • Work on morphology to ensure permanent supply of secondary channels.


Mitigation measures2
Mitigation measures of stream.

  • Efficiency:

    • Only ≈ 5% salmonid redds dewatered, instead of 30% without base flow increase.

    • Significant decrease of fry mortality in connected secondary channels.


Effects on electricity production
Effects on electricity production of stream.

  • There were compensations for the losses of electricity production. In general, losses of production varied between 0,5 % to 2% of the total potential of peak production.

  • They remained quite limited because of the line organization. Only the production of the last hydropower plant is really affected.

  • All decisions of flow changes were made ​​in consultation with the electricity company


Hydropeaking and minimum flow the french approach p baran

Minimum flow of stream.


Evolution of low flow
Evolution of low flow of stream.

  • Analysis of the evolution of low flow at large scale during the 3 last decades (Guintoli and Renard, 2010).

    • Volume

    • Duration

    • Time (begining and end)


Evolution of low flow1
Evolution of low flow of stream.

  • Significant evolution of low flow conditions.


Fish communities and low flow
Fish communities and low flow of stream.

Changes in fish communities in relation to low flow conditions




French approach1
French approach of stream.

  • The French Water Law impose minimum values of flow :

    • 5% to 10% of mean annual flow in 2014 for all dams and weirs

  • Locally, for each dams or weirs, the value of minimum flow can be increased based on study using microhabitat methodology.


Conclusions
Conclusions of stream.

  • Modifications of flow regime are very important in France for a large part of water bodies.

  • A focus was made on hydroelectricity use with :

    • an evaluation at large scale for hydropeaking effects on flow regime,

    • the definition of mitigation measures at small scale

  • No direct relationships were established with biological index related to ecological status assessment of water bodies.