The Fifth GEF Biennial International Waters Conference, Cairns, 26-29 October 2009
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The Fifth GEF Biennial International Waters Conference, Cairns, 26-29 October 2009 Global Changes and Water Resources Workshop The Merguellil catchment (central Tunisia): towards an integrated study of water resources and water uses Christian LEDUC Gestion de l'Eau, Acteurs, Usages IRD, UMR G-EAU, Montpellier, France leduc@ird. fr
description
Gestion de l'Eau, Acteurs, Usages. The Fifth GEF Biennial International Waters Conference, Cairns, 26-29 October 2009 Global Changes and Water Resources Workshop The Merguellil catchment (central Tunisia): towards an integrated study of water resources and water uses. Christian LEDUC. - PowerPoint PPT Presentation
Transcript of The Fifth GEF Biennial International Waters Conference, Cairns, 26-29 October 2009
The Fifth GEF Biennial International Waters Conference, Cairns, 26-29 October 2009
Global Changes and Water Resources Workshop
The Merguellil catchment (central Tunisia): towards an integrated study of
water resources and water uses
Christian LEDUC
Gestion de l'Eau, Acteurs, Usages
IRD, UMR G-EAU, Montpellier, France
Impacts of the Global Change on the hydrological cycle
An attempt to integrate studies at a relevant scale
A situation typical of the Mediterranean environment (and many other semi-arid cases)
GEF International Waters Conference, Cairns, Oct. 2009, Global Changes and Water Resources Workshop
Tunis
250 mm
500 mm
Merguellil
National context: limited resources, highly variable in time and space
increasing demand for population, agriculture, tourism
decision of a maximum use of WR (goal of nearly 100 %)
Regional context: semi-arid catchment (> 2000 km2)
increasing uses up to overexploitation
water export to the coastal region
GEF International Waters Conference, Cairns, Oct. 2009, Global Changes and Water Resources Workshop
Kairouan
Global change
Rainfall: 200 to 550 mm.yr-1
highly variable: ex 1969 no long-term trend
Increasing population (0.25 % yr-1 1994-2004 2.3 % yr-1 1984-1994)
Intensified agriculturegrazing lands turned into fieldstraditional crops replaced by irrigated crops
Many water and soil conservation works
Big dams
GEF International Waters Conference, Cairns, Oct. 2009, Global Changes and Water Resources Workshop
Water and soil conservation works
Increasing number of Water/Soil Conservation works (bench terraces, 48 small dams)
For limiting erosion on the slopessilting up of the big El Haouareb dam
Rarely in agreement with local customs and wishes
Increase in green water, locallyIncrease in stored water (small reservoirs)Clear decrease in blue water at the catchment outlet
Fundamental maintenance of WSCW:quick loss of efficiencyfinal result often worse than nothing
Limited development of new uses from the new storages
2003
1970
1988
GEF International Waters Conference, Cairns, Oct. 2009, Global Changes and Water Resources Workshop
The El Haouareb big dam
Protection against floods + Provision of water to an irrigated scheme
Total change in groundwater recharge(location, processes, flow, quality):
- no river flow downstream - the dam is often dried up - ≈ 60 % of the dam water infiltrates to
the karst - tracing of the reservoir evaporation
(reservoir, downstream)
Groundwater upstream
3 "small" aquifers1 deliberately overexploited by the State for
exporting drinking water to the coast
Enhanced leakage from the rivers to the aquifers Increasing pumping for irrigation and potable water
Groundwater upstream
1 thick aquifer, overexploited for potable water, public and private irrigation
No enforcement of the law protecting the aquifer
90
95
100
105
janv-92 janv-94 janv-96 janv-98 Janvier00 janv-02
Some technical remarks
Contradictory impacts of conservation works:prevent siltation but decrease the exploitable water resource
The big dam is often empty, because of the unexpected karstic loss
Physical models propose contradictory explanations
Possible consequences of overexploitation:deeper pumping more difficult and more expensiveresort to more salted water
GEF International Waters Conference, Cairns, Oct. 2009, Global Changes and Water Resources Workshop
GEF International Waters Conference, Cairns, Oct. 2009, Global Changes and Water Resources Workshop
Socio-economical surveys
Typology of farms and farmers
Behaviour of farmers facing changesin their physical environment (climate, soil fertility)in the regulations (law, water price, technical constraints)in the external market
Cooperation/competition between farmers (land rental, water sale) (family vs speculators, large vs small)
Spatial scales of benefit: personal-local-regional-national
GEF International Waters Conference, Cairns, Oct. 2009, Global Changes and Water Resources Workshop
Socio-economical surveys
Proposal of measures for protecting the water resourceacceptability - efficiency
Unexpected impacts:increasing irrigated areas after subsidising drip irrigation
Social equity vs profitability
Institutional analysis lack of coordination inside the same Ministrylimited involvement in local top-down associations
Conclusion
To manage together water supply and water demand
To integrate technical and socio-economical aspects
To build long-term sustainable proposals
Natural and human complexity beyond our models
Already in official files:
interconnection of big dams in Central Tunisiatransfer channels from Northern Tunisia
GEF International Waters Conference, Cairns, Oct. 2009, Global Changes and Water Resources Workshop
GEF International Waters Conference, Cairns, Oct. 2009, Global Changes and Water Resources Workshop
Second International Conference on Climate, Sustainability andDevelopment in Semi-arid Regions - ICID 2010
Fortaleza, 16-20 August 2010www.icid18.org
Contribution to the Rio+20 UN conference on development and environment1) Climate and Environment2) Climate and Sustainable Development3) Governance and Sustainable Development4) Policy Processes and Institutions.
Submissions of papers, panels, round tables welcome
