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Les zones méditerranéennes et semi - arides sont caractérisées par des régimespluviométriques irréguliers dans le temps et dans l'espace. L'érosion hydrique des bassinsversants et la sédimentation des cours d'eau constituent des phénomènes complexes trèsrépandus qui posent de nombreux problèmes aux ingénieurs chargés des projets de mise envaleur. En raison de son ampleur, cette érosion constitue une contrainte majeure audéveloppement de l'agriculture et à la promotion des activités rurales en Algérie. Uneapproche statistique de quantification des apports solides est développée dans cette étude.Les données utilisées sont recueillies au niveau de cinq sous-bassins du bassin versant del'Oued Mina drainés par les stations hydrométriques, en amont du barrage de Sidi M'hamed BenAouda. La période d'observation s'étale sur 22 ans (1973 à 1995). Il existe une grandevariabilité inter-annuelle et intrannuelle des apports liquides et solides. En plus de cettevariation temporelle, il a été remarqué une variabilité spatiale des apports solides etliquides.Les valeurs maximales du transport solide sont enregistrées au début d'automne et à lafin du printemps. Le transport solide d'automne reste le plus élevé, dépassantsignificativement les autres saisons. Cette variabilité trouve son explication dans lapauvreté du couvert végétal durant cette saison et la nature agressive des pluies d'automne.La charge spécifique du bassin versant de l'oued Haddad est de l'ordre de 212t/km2/an. Le bassin versant de l'oued Taht a une charge spécifiqueinférieure à celle du bassin de l'oued Haddad (Ds=191 t/km2/an). Lesbassins versants de l'oued el Abd présentent des charges spécifiques de l'ordre de 117t/km2/an à Ain El Hamara et de 65 t/km2/an àTakhmaret. La charge spécifique de l'oued Mina au barrage de Sidi M'hamed Ben Aouda est de160 t/km2/an.Des modèles mathématiques liant l'apport solide au coefficient d'écoulement ont étéproposés pour les cinq sous-bassins drainés par les stations hydrométriques.Mediterranean and semi - arid zones are characterized by an aggressive climate and byirregular and violent rainfall events. Water-induced erosion in river basins and riversedimentation constitute a complex phenomenon, which poses many problems for the engineersresponsible for development projects. This phenomenon constitutes a major constraintlimiting agricultural development in Algeria. We propose a statistical approach to quantifythe solid yield at different gauging sites.The data were collected at five sites in the Oued Mina basin (upstream of the Sidi Mehamed Ben Aouda dam). The observation period covered 22 years, from 1973 to 1995. Theresults showed a high inter-annual and annual variability of the liquid discharge and solidyields; the coefficient of variation exceeded 60% in all cases. In addition to this temporalvariation, we noted a variability of the solid yields and liquid discharge among thedifferent sites. Analysis of the monthly solid yields shows that the autumn seasoncontributes a large proportion of the annual solid yield (more than 40%) for the differentbasins. Tranport of solids in the Oued Mina and its effluents is highly variable in spaceand time. This variability is due primarily to the pluviometric regime, the vegetation coverand the lithology. In general, the seasonal variations of the solid contributions followthose of the liquid flow. The maximum values of the solid discharges, for all basins, areobserved at the beginning of autumn and the end of spring. Generally, the monthly minimalsolid yields are recorded in summer. This season is characterized by low rainfall andconsequently a weak surface flow. However, the minimal solid yields do not necessarilycorrespond to the month characterized by the lowest liquid discharge. The autumn contributes31% to the annual liquid flow and 51% to the annual solid yields of the Oued Mina area atWadi El Abtal station; corresponding values are (26 %, 33 %), (33%, 53 %), (29%, 46%) and(36%, 48 %) at the stations of Sidi A.E.K Djillali, Ain Hamara, Kef Mehboula and Takhmaret,respectively. The autumn solid transport remains highest, significantly exceeding the otherseasons. This variability is explained by the variation in vegetation cover (bare ground)during the year and the aggressive nature of the autumn rains. Because of these two factors,the first autumn flood transports considerable quantities of sediments after a long dryseason characterized by high temperatures and destruction of the soil aggregates by thesetemperatures. The energy produced by the first rains and the low degree of vegetative coverrate in this season also contribute to this increase in autumn. The Oued Haddad basinpresents a high specific degradation compared to the other basins (Ds=212t/km2/an). This impoverishment of the soil is very visible at thissite. It is due to factors favouring erosion : steep topography and discontinuous vegetativecover, which protects the ground poorly. The Oued That basin, which has a topographyfavouring surface flow and abundant rains, has a specific degradation lower than the OuedHaddad basin (Ds=191 t/km2/an). The basins of Oued El Abd present aspecific degradation about 117 t/km2/an at Ain El Hamara station andabout 65 t/km2/an at Takhmaret station. The Oued Mina at Sidi M'hamedBen Aouda dam gives a specific degradation about 396 t/km2/an.The runoff coefficient explains a large part of the variance of the solid yield (morethan 60%). This coefficient depends intrinsically on lithology, geology, vegetative cover,topography and the hydrological and pluviometric regimes. By the introduction of thisparameter, we sought to explain solid transport by the explanatory variables of thisphenomenon. The result was very encouraging, considering the percentage of the explainedvariance (more than 60%). Following this analysis, mathematical models are proposed,connecting the solid yield to the runoff coefficient. The determinations coefficients areequal to : 0.79; 0.61; 0.64; 0.78; 0.65 for the stations of oued Al Abtal, Sidi AbdelkaderDjillali, Ain Hamara, Kef Mehboula and Takhmaret, respectively

Variabilité spatio-temporelle des apports liquide et solide en zone semi-aride. Cas du bassin versant de l'oued Mina (nord-ouest algérien)