3rd HyMeX workshop 1-4 June 2009 Heraklion (Gournes), Crete-Greece
Contribution to the study of fluctuations in rainfall in west Algeria and its impact on land use Djamila Harrache (Faculty of Science, University Djillali Liabès (Sidi -Bel -Abbès, Algeria)); Khéloufi Benabdeli
The vegetable production is strategic for economy and ecology of any space; it remains subordinate to the water resource and especially to precipitations. For each 100 grams of produced green matter, water is present between 60 and 95%; the plant absorbs on average between 1 and 1.5 liter of water to manufacture 3 to 4 grams of dry matter. In Algeria, the average water consumption for one hectare is estimated at:
- 3.500 m3 for cereals,
- 6.000 m3 for the fodder plants,
- 2.300 m3 for the oats,
- 12.000 m3 for citrus fruits,
- 1.000 m3 for a oak centenary.
For the strategic cultures that are the cereals in Algeria, the contribution of water is natural and is done exclusively by precipitations. These last know an important fluctuation and act on production efficiency and on proliferation of undesirable grasses.
To analyze the fluctuation of precipitations in Algerian Tell, strategic geographical area for the agricultural production and where 95% of the stoppings are localized, over two periods: 1913-1938 and 1985-2005 allows to give some capital indications for a new approach as regards exploitation of spaces. The following data show us a rather remarkable reduction.
| Périods | Maximum Précipitations | Minimal Précipitations |
| 1913-1938 | 680 mm | 545 mm |
| 1985-2005 | 535 mm | 465 mm |
| Differences | - 145 mm | -80 mm |
| Percentage | 22% | 15% |
For the recent period the evolution of precipitations is characterized by a frequency of annual tranches of precipitations:
- 35% between 200 and 300 mm.
- 45% between 300 and 400 mm
- 20% more than 400 and lower than 450 mm
The tendency towards a reduction in precipitations is clearly perceptible and asks for a new space management method centered on a recutting territory in homoecologic zone with preponderance to the pluviometric section. Other orientations, like a reduction of plantation densities, a search for varieties which consume less water and farming techniques rising from arid cultural, will be applied.
