hydropeaking and minimum flow : the french approach. p. baran cis ecostat - hydromorpholgy workshop...

Hydropeaking and minimum flow : the French approach.

P. Baran

CIS ECOSTAT - HYDROMORPHOLGY WORKSHOP

12th and 13th June 2012 - Brussels

Pôle Ecohydraulique

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 of water storage

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 context for hydroelectricity

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.

Garonne - Saint-Béat - 2006

0.0

23.6

47.2

70.8

94.4

1/1 1/2 4/3 4/4 5/5 5/6 6/7 6/8 6/9 7/10 7/11 8/12Date

Débi

t (m

3/s

)

Hydropeaking

Focus on hydropeaking

More than 150 hydroelectric schemes managed by hydropeaking in France.

≈ 3000 kms of streams concerned by hydropeaking.

7

Garonne - Saint-Béat - 2006

0.0

23.6

47.2

70.8

94.4

1/1 1/2 4/3 4/4 5/5 5/6 6/7 6/8 6/9 7/10 7/11 8/12Date

Débi

t (m

3 /s)

Corrèze - Corrèze - 2006Hydrologie naturelle

0.0

5.6

11.2

16.8

22.4

1/1 1/2 4/3 4/4 5/5 5/6 6/7 6/8 6/9 7/10 7/11 8/12Date

Déb

it (

m3 /s

)

Comparaison des débit moyens journaliers (QMJ) et des débits à pas de temps variable (QTVAR) à Argentat.

Comparaison des débit moyens journaliers (QMJ) et des débits à pas de temps variable (QTVAR) à Argentat.

Analysis of flow regime

The French approach

1. Identifications of flow modifications induced by hydropeaking

8

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

89

90

91

92

93

94

95

96

97

98

99

0 500 1000 1500 2000 2500 3000

Distance à partir de l'aval (m)

Alt

itu

de

rela

tive

(m

)

Thalweg

Modèle 20 m3/s

Mesure 20 m3/s

Modèle 30 m3/s

Mesure 30 m3/s

Modèle 117 m3/s

Mesure 117 m3/s

Modèle 200 m3/s

Mesure 200 m3/s

Modèle 303 m3/s

Mesure 303 m3/s

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

The French approach

9

Surface en eau des 7 frayères

15000

17000

19000

21000

23000

0 50 100 150 200 250 300

Débit (m3/s)

Sur

face

(m²)

Dordogne - Argentat - 2008

0

50

100

150

200

250

300

350

400

1/1 16/1 31/1 15/2 1/3 16/3 31/3 15/4 30/4 15/5 30/5

DateD

ébit

(m

3 /s)

The French approach

3. Proposal of mitigation measures and assessment

Approach based on hydraulic models and habitat mapping

Index of hydrological perturbation

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

Garonne - Saint-Béat - 2006Affected by hydropeaking

0.0

23.6

47.2

70.8

94.4

1/1 1/2 4/3 4/4 5/5 5/6 6/7 6/8 6/9 7/10 7/11 8/12Date

Dis

char

ge

(m3 /s

)

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 disturbance

For each year : Number of hydropeaks Statistical characteristics of :

base flow, maximum flow, range, rate of change,

Base flowRangeRate of change

Nu

mb

er o

f h

ydro

pea

ks

Maronne - Basteyroux - 2006

0.0

20.3

40.6

60.9

81.2

1/1 1/2 4/3 4/4 5/5 5/6 6/7 6/8 6/9 7/10 7/11 8/12

Date

Dic

har

ge

(m3 /s

)

Garonne - Saint-Béat - 2006

0.0

23.6

47.2

70.8

94.4

1/1 1/2 4/3 4/4 5/5 5/6 6/7 6/8 6/9 7/10 7/11 8/12Date

Dis

char

ge

(m3/s

)

Dordogne - Argentat - 2006

0

107

214

321

428

1/1 1/2 4/3 4/4 5/5 5/6 6/7 6/8 6/9 7/10 7/11 8/12Date

Dis

char

ge

(m3 /s

)

Daily hydropeaks

Hourly hydropeaks

Weekly hydropeaks

Characterization of hydrologic perturbation: Construction underway of an indicator of hydrologic

perturbation due to hydropeaking events.

Level Colour Levels of hydrologic perturbation

due to hydropeaking events

0 Hydrology natural or hardly disturbed.

1 BlueNoticeable hydrologic perturbation.

2 Green Hydrologic perturbation marked.

3 YellowHydrologic perturbation very marked.

4 Orange Severe hydrologic perturbation.

5 RedVery severe hydrologic perturbation.

Based on discriminant analysis :

-base flow,-maximum flow,-range,-rate of change,- number of hydropeaks

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.

Saint-Béat - 2006

Chaum - 2006

Valentine - 2006Upstream

Downstream

Global situation in France:

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

Impact of hydrological perturbations 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

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.

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 habitat

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

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

La Dordogne à Argentat en 2006

0.0

0.3

0.6

0.9

1.2

1.5

1.8

2.1

2.4

2.7

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4

Débit de base (proportion du module)

Am

plit

ud

e (

pro

po

rtio

n d

u m

od

ule

)

> 1

0.25 - 0.5

0 - 0.25

Gradient (module/heure)

Line of lakes and hydropower plants

La Maronne à Basteyroux en 2006

0.0

0.3

0.6

0.9

1.2

1.5

1.8

2.1

2.4

2.7

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4

Débit de base (proportion du module)

Am

plit

ud

e (

pro

po

rtio

n d

u m

od

ule

)

0.5 - 1

0.25 - 0.5

0 - 0.25

Gradient (module/heure)

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

Impacts on fish habitat

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).

During a hydropeak Back to base flow

Mitigation measures

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 measures

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 measures

Efficiency: Only ≈ 5% salmonid redds dewatered, instead of 30% without base

flow increase.

Significant decrease of fry mortality in connected secondary channels.

MaronneBras RD de l'Hospital

0

86.4

44.8

66.1

123.1

0

20

40

60

80

100

120

140

≤ 2005 2006 2007 2008 2009

Den

sit

és d

e 0

+p

ou

r 1

00 m

²

Effects on electricity production

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

Minimum flow

Evolution of low flow 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 flow Significant evolution of low flow conditions.

Fish communities and low flow

Changes in fish communities in relation to

low flow conditions

Fish communities and low flow

Fish communities and low flow

0

200

400

600

800

1000

1200

1400

1600

1800

2000

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

QMNA (m3/s)

Bio

mas

ses

de

TR

F (e

n g

)

0

500

1000

1500

2000

2500

3000

3500

0 0.1 0.2 0.3 0.4 0.5

QMNA (en m3/s)

Bio

ma

ss

es

de

TR

F (

en

g)

French approach

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

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.