WATER HARVESTING AND CC ADAPTATION IN THE DRY AREAS OF TUNISIA

1. Regional Consultation Meeting Climate Change Impacts in the Arab Region: Water Scarcity, Drought, and Population Mobility الاجتماع التشاوري الإقليمي "تأثيرات تغير المناخ في المنطقة العربية: ندرة المياه، والجفاف، وتنقل السكان" 16-15 سبتمبر/أيلول٢٠١٠ 2010 15-16 September دمشق، سورياDamascus , Syria – WATER HARVESTING AND CC ADAPTATION IN THE DRY AREAS OF TUNISIA Dr. Mohamed OUESSAR Institut des Régions Arides (IRA) 4119 – Médenine – Tunisie Tél: 216-75633005; Fax: +216-75633006 Email: Med.Ouessar@ira.agrinet.tn

2. OUTLINE

3. Introduction • Basic principles • Development • Overview of WH in Tunisia • CC in Tunisia • WH & CC adaptation • Conclusions & prospects

4. INTRODUCTION

5. The dry areas are characterized by: • rainfall is rare, variable and torrential • Insufficient to meet the basic needs for crop production, • Poorly distributed over the growing season  risky farming • Runoff can cause erosion and be lost later by evaporation from swamps ‘salt sinks”, • High temperature  evapotranspiration • Shallow and poor soils  degradation, moisture stress  desertification • Dominating rainfedagriculture

6. BASIC PRINCIPLE

7. Depriving part of the land of its share of rain, which is usually small and non productive, and adding it to the share of another part in order to bring the available water amount closer to the water requirements of crops (Oweis et al., 2001) Collection area Runoff Reservoir Target area

8. 200 150 mm Runoff harvesting – additional 35% of annual rainfall

9. DEVELOPMENT OF WH

10. As long as the people have inhabited the dry areas and made cultivation, they have harvested water. • In southern Jordan early WH structures are believed to have been constructed around 5000 years ago, • Southern Mesopotamia: 4500 BC, • Negev desert: 1000 BC, • Yemen (Tihama): spreading system dating 1000 years BC • Pakistan (Balauchistan): Khuskaba and salaiba systems • Tunisia: Jessour, meskat and cisterns, • Egypt (North west and Sina): wadi bed systems and cisterns, • Moroccco, Syria, Iran, Oman, : Groundwater galleries (fouggara, falej, …).

11. OVERVIEW OF WHT IN TUNISIA Ben Mechlia & Ouessar, 2004; Ouessar, 2007

12. 1500 1000 750 500 400 300 200 100 200

13. Agro-ecological zones               200Isohyet         • LEGENDS • Cereals • Forests • Irrigation • Fruit trees • Rangelands • 690 Altitude    Wadi Sebkha

14. Catchment Jessour Dike Cropping Area 400 100

15. CC IN TUNISIA Minis. Agriculture, 2007

16. Temperature increase (in °C) for the 2020 (left) and 2050 (right) horizons.

17. Average annual rainfall decrease (in %) for the 2020 (left) and 2050 (right) horizons.

18. WH & CC ADAPTATION

19. Case of Meskat Snane et al., 1991

20. ETa in a Meskat system for different CCR and annual rainfall (green: 413 mm; Red: 290 mm)

21. Case of Tabias Nasri et al., 2004

23. Case of Jessour

24. Water balance in of jessour Hyd. Year: type of the hydrological year ETrel: relative ETa 1: ETa with only rainfall on the terrace 2: ETa with rainfall and runoff on the terrace 3: ETa with rainfall, runoff and supplemental irrigation

25. Watershed treatment Schiettecatte et al., 2005; Ouessar, 2007; Ouessar et al. 2009

27. SC0 SC2 VD D N W VW VD

28. Vulnerability of olive groves to CC Sghaier et al., 2010

30. CONCLUSIONS & PROSPECTS

31. Water harvesting techniques have been developed since antiquity to cope with climate variability in the dry areas. • They played major role in the development of rainfed agriculture in addition of providing other ecosystem services • With the prospect of CC, those systems/techniques would be more useful. Therefore, they need to be well considered in the national/regional strategies for adaptation with CC.

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33. Thank you