PRECIPITATIONS ANALYSIS IN THE NORT-WEST OF ALGERIA ? IMPACT ON THE CEREAL FARMING PRODUCTION

Mohamed MEDDI, K. KETROUCI, A. MATARI

Résumé


Abstract:
Algeria and especially the West, had known several droughts during the last century, the
Fourties and the Eighties until our days. The recent was characterized by its space magnitude,
its intensity and its major and significant impact which is the reduction in the water resources
and reduction of cereals farming production. Accordingly, we will propose to study the
rainfall data and cereals farming production observed in the Western of Algeria. Therefore to
establish the drought characteristics and to study the consequences of rainfall reduction on
cereals farming production.
This study was based on the analysis of rainfall data and those of the cereals farming
production observed in the west of Algeria.
The choice of 23 pluviometric stations is based on the historical study. These stations whish
have been operating since 1968, cover all the space of the west regional Algeria. The results
provided by the principal components analysis, to develop a regional groups of our studied
zone, show a good space coherence between the stations. We note the existence of three
distinct regional groups, formed by a group of stations having a similar behavior. This
analysis showed a succession of two phases : a long rainy episode which extended between
the beginning of the Fifties and the end of the Seventies; and a poor period which has started
at the beginning of the Eighties and persists until now. The winter rains, during the last
period, generally knew a fall for the three standard stations (Mascara, Maghnia and Sougeur),
whereas the spring rains became higher during the two last decades. The study of the dry and
rainy sequences by the the MARKOV chains, showed that the dry sequences have an average
length which increases with the threshold grows. The seasonal distribution of these sequences
is in relation with the cereals farming production. The representation of the chronology of the
series of cereals farming production shows the rise of it?s tendency. From our opinion, this
tendency is due to the progress in farming techniques. After the correction of this anthropic
tendency, we analyzed the relation yield-rain. This confirms the production fall and shows its
connecting with precipitations.
The analysis of the minimal and maximum temperature permitted to detect an increase in
both the minimas and maximas at Oran?s station during the two last decades. This tendency
of the temperature generated an acceleration of the evapotranspiration which is accompanied
by a lack of water in the ground. The rain reduction associated with the considerable
temperatureduring the two last decades, influenced the cereal yields.

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