Contribution A L’etude De La Secheresse Et Concepts Des Modeles Probabilistes « Cas De La Region De Souk-ahras, Algerie »

Résumé: In the semi-arid region of Algeria, We have experienced several periods of drought are characterized by rainfall deficit and very low flows of the main wadis watershed. During dry periods, the water resources surface and, therefore, the stored volumes suffered a sharp decline. Sometimes it becomes difficult to meet the demand in drinking water, and also that agriculture. To better manage this situation, knowledge of climatic factors and characterization of drought by estimating indicators are essential. This study aims to show the existence of climate variability in the North East region of Algeria in the watershed north of Medjerda and understand its impact on the supply of water resources. To do this, various data (rainfall, temperature, the reference evapotranspiration, historical maps of rainfall, liquid flows) and methods (reduced centered index, the index of deviation from the mean, building intensity curves duration frequencies) were used. The application of reduced centered clues and the deviation from the average for rainfall and hydrological data showed a climate variability characterized by alternating wet phases, normal and dry. These statistical methods indicate reduced rainfall which is apparent in the 80s and 90s, where a long period of drought phenomenon of 3 successive years is observed towards the end of the 80s and early 90s. The evolution of the reference evapotranspiration and temperature is reversed compared to that of rainfall. The increase in temperature adversely affects the availability of water resources in the study area. This influence that results in increased evaporation losses. The history of rainfall maps indicates that the study area indicates a real shift in rainfall zones. The manifestations of this climatic variability affect water resources. Thus the results of the index of the deviation from the average liquid intake at the dam AinDalia show a deficit on the same date of the succession of years of drought. The change of climate variables in decades (1980-1990-2000) produced in the study area more frequent rainfall during the summer that has the same characteristics of convective rain. They have short durations and high intensities. For proper management of water resources, probabilistic models were made. KEYWORDS: Dryness, frequency analysis, fluctuation, climate variability, catchment area, Souk-Ahras.

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