1. No category

Workshop on GCC and Implications for Water Resource Management
Changes in the low flows, what says hydrology?
How to adapt irrigation development?
Cases studies in France and Morocco
Henri TARDIEU
[email protected]
CLIMATE WS Sacramento 4-10-2007
08/07/2008
n° 1
Changes in the low flows, what says hydrology?
How to adapt irrigation development?
Cases studies in France and Morocco
Which actual changes in the low flows?
Three Questions about global change
CLIMATE WS Sacramento 4-10-2007
08/07/2008
n° 2
Which actual changes in the low flows?
CLIMATE WS Sacramento 4-10-2007
08/07/2008
n° 3
Which actual changes in the low flows?
Data on low flows are not so easy to get:
- Gauging properly the water velocity need a stable river
morphology
- Natural low flows are influenced by human actions
(withdrawals and dam releases)
In France, 50% of what seem non-stationarities, are
caused by errors of measurement and by anthropic
influences
(M. Lang, B. Renard 2007)
CLIMATE WS Sacramento 4-10-2007
08/07/2008
n° 4
Which actual changes in the low flows?
France
Morocco
CLIMATE WS Sacramento 4-10-2007
08/07/2008
n° 5
Which actual changes in the low flows?
Two examples in South-Western France
Midouze
Gascony Rivers
CLIMATE WS Sacramento 4-10-2007
08/07/2008
n° 6
Which actual changes in the low flows?
Gascony rivers : which resources in the future?
•Water users :
–fish & wildlife and tourism need 250 Mm3 to
strengthen low flows
–200 000 inhabitants consume 13 Mm3
–51 000 irrigated hectares consume 95 Mm3
•Water resources :
–Neste Canal diverts 250 Mm3 out of river Neste
coming from Pyrenees Mountains
–the stored resources : 100 Mm3
CLIMATE WS Sacramento 4-10-2007
08/07/2008
n° 7
Which actual changes in the low flows?
Resources diverted from Pyrenees mountains :
Apports naturels de la Neste dérivables par le canal
(Qreserve=4m3, Qplafond=14m3/s)
400
Annual average flow … more instable
but probably constant
350
Volume dérivable (hm 3)
300
250
200
Période annuelle
Juillet-Août
150
low flow (JA)…decreasing – 20%
100
as predicted by MeteoFrance GCC models
50
0
1960
1965
1970
1975
1980
1985
1990
1995
2000
Année
Divertible resources
Year
July-August
Old series 30 ys 1961-1991
278 hm3
45 hm3
New series 13 ys 1992-2004
280 hm3
35 hm3
CLIMATE WS Sacramento 4-10-2007
08/07/2008
n° 8
Which actual changes in the low flows?
Gascony rivers :
Are the development principles still sustainable ?
Yes, irrigation development is “hydrologically”
sustainable but with adaptation to climate change:
•diversion of mountain flow should decrease in summer
•new dams could be securely filled with water diverted in
winter
CLIMATE WS Sacramento 4-10-2007
08/07/2008
n° 9
Which actual changes in the low flows?
Midouze Basin, in the « Landes » forest
•Forest = 70 % of the basin area
•Forest Productivity increases from 4m3/ha to 11m3/ha
•Irrigated maize pumping in rivers, area stabilized for 15 years
•Groundwater sustaining river flows but no storages
CLIMATE WS Sacramento 4-10-2007
08/07/2008
n° 10
Which actual changes in the low flows?
Stable rainfall but decreasing river flows, why?
Pluies moyennes sur le bassin de
mars à juillet
Débit détiage de la Midouze 1967 à 2004
13
600
12
500
11
10
400
9
8
300
7
200
6
5
100
4
What about CO2 impact on biomass
production and water demand?
CLIMATE WS Sacramento 4-10-2007
08/07/2008
n° 11
20
03
20
01
19
99
19
97
19
95
19
93
19
91
19
89
19
87
19
85
19
83
19
81
19
79
19
77
19
75
19
73
19
71
19
69
3
19
67
0
Which actual changes in the low flows?
Midouze Basin :
Are the development principles still sustainable ?
If it is only based on the natural river flow, irrigation
development is no more “hydrologically” sustainable :
•Adaptation means that a larger part of the decreasing
natural flow should be reserved for environment
•Is it realistic to compensate decreasing flow with new
storages?
•Decision on new storages are waiting for a clear
explanation of the low-flow decrease…
CLIMATE WS Sacramento 4-10-2007
08/07/2008
n° 12
Which actual changes in the low flows?
Oum Er Rbia Basin - Morocco
a « Closed Basin » where anthropic pressure overpasses river capacity:
www.iucn.org/themes/wani/eatlas/
CLIMATE WS Sacramento 4-10-2007
08/07/2008
n° 13
Which actual changes in the low flows?
Oum Er Rbia Basin - Morocco
Casablanca
5200 Mm3 stored
Doukkala
CLIMATE WS Sacramento 4-10-2007
08/07/2008
n° 14
Which actual changes in the low flows?
Oum ErBia Basin resources dramatically decrease !
Old Series
39 years 1941-1979
Total Series
60 years 1941-2000
New Series
21 years 1980-2000
4 080 hm3
3 520 hm3
2 480 hm3
- 40% in annual average low flow:
interannual cycles or a lasting
decrease of the annual water
resources due to climate change ?
CLIMATE WS Sacramento 4-10-2007
08/07/2008
n° 15
Which actual changes in the low flows?
Bin El Ouidane storage will no longer be filled ,
threat on allocation to irrigation !
Apports annuels au réservoir de Bin el Ouidane
Capacité 1307 Mm3
3 000
2 500
2 000
1 500
Irrigation
Allocation Plan
945 hm3
1 000
500
19
41
19
43
19
45
19
47
19
49
19
51
19
53
19
55
19
57
19
59
19
61
19
63
19
65
19
67
19
69
19
71
19
73
19
75
19
77
19
79
19
81
19
83
19
85
19
87
19
89
19
91
19
93
19
95
19
97
19
99
0
Old Series
39 y.
1941-1979
Total Series
60 y.
1941-2000
New Series
21 y.
1980-2000
For the last 10 years
irrigation allocation
1030 hm3
could only be 30%
620 hm3 of the design
1250 hm3
CLIMATE WS Sacramento 4-10-2007
08/07/2008
n° 16
Which actual changes in the low flows?
Oum Er Rbia Basin - Morocco :
Are the development principles still sustainable ?
No : irrigation development becomes impossible:
•Irrigated area should decrease to limit the risks
•Considering existing storages and presently decreasing water
resources, new dams are useless.
•Which solution for development ? (water saving is not enough)
–transfer from the not yet closed Sebou Basin ?
–desalinization but with which energy ?
CLIMATE WS Sacramento 4-10-2007
08/07/2008
n° 17
Which actual changes in the low flows?
Conclusions
•Hydrology shows actual changes in low flows, but they are
very specific to each basin. No general assertion !
•Principles for irrigated agriculture development should be
“hydrologically” sustainable.
•Develop anxiety in society is pointless. But in some cases
developers and politicians should urgently adapt water
management and development policies.
CLIMATE WS Sacramento 4-10-2007
08/07/2008
n° 18
Three Questions about global change
CLIMATE WS Sacramento 4-10-2007
08/07/2008
n° 19
Three Questions about global change
How to use GCC models to make consistent forecasts
of the future flows
How to include CO2 impact on biomass, on green
water and finally on low flows ?
Apports naturels de la Neste dérivables par le canal
(Qreserve=4m3, Qplafond=14m3/s)
400
Débit détiage de la Midouze 1967 à 2004
Apports au réservoir de Bin El Ouidane - Capacité 945Mm3
350
13
2 500
12
300
2 000
11
1 500
250
1 000
10
500
9
19
95
19
97
19
99
19
89
19
91
19
93
19
85
19
83
19
87
19
77
19
79
19
81
19
71
19
73
19
75
19
65
19
67
19
69
19
59
19
61
19
63
19
53
19
55
19
57
19
47
19
49
19
51
19
41
8
Juillet-Août
150
19
43
0
Période annuelle
19
45
200
7
100
6
5
50
4
20
03
20
01
19
99
19
97
19
95
19
93
19
91
19
89
19
87
3
19
85
2000
19
81
1995
19
83
1990
19
77
1985
19
79
1980
19
73
1975
19
75
1970
19
69
1965
19
71
0
1960
19
67
Volume dérivable (hm 3)
3 000
Année
CLIMATE WS Sacramento 4-10-2007
08/07/2008
n° 20
Three Questions about global change
In view of non-stationarity of low flows, how to manage
water sharing in the future?
A complex issue for IWRM with social and political
implications!
?
An impossible choice
CLIMATE WS Sacramento 4-10-2007
08/07/2008
n° 21
Three Questions about global change
Will climate change contribute to global supply-demand
inbalance for agriculture?
Which effects on the poorest? Will poor farmers receive a
share of the increased agricultural prices?
Prix des céréales en France du 30 juin 2004 au 30 juin 2007)
CLIMATE WS Sacramento 4-10-2007
08/07/2008
n° 22
Merci pour votre attention
CLIMATE WS Sacramento 4-10-2007
08/07/2008
n° 23