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In the perspective of current climate variability and the impact of human activities on water overexploitation, it is essential to analyze dry and wet episodes for a better prevention and rationalization of water resources. The Mediterranean region and particularly the southern shore, is a drought sensitive area. Algeria, like most Mediterranean countries has experienced alternating dry and wet periods in recent decades. Several climatic events have had a negative impact on agriculture, industry and drinking water supply. As a result, human societies and ecosystems are under increasing threat requiring new adaptations of life and economic models to support these upheavals. The present study focuses on monitoring of the meteorological drought evolution in the Isser wadi watershed, located in the north-central part of Algeria, based on available rainfall data covering a 43-year period from 1973 to 2016. The current study has made it possible to account for the extreme variability of rainfall in this watershed. In order to do this, different indices were studied in this work, namely the normalized precipitation index SPI, the rainfall deficit index RDI, and the drought index DI. All The obtained results have highlighted the severe and sustainable character of the climatic drought observed in the Isser basin from 1973 to 2002 as well as the return to a wet phase, well pronounced in the north of the basin from 2003 to 2016. Finally, in order to better understand this work, index maps tools for decision-making have been established. [ABSTRACT FROM AUTHOR]

Wadi Isser watershed (4149 km2), located in the North of Algeria, has experienced a significant rainfall variability during the last four decades. In order to characterize this variability and determine its spatial extension, by means of the analysis of the rainfall data measured in twenty-seven (27) stations, the following study was conducted. The analysis of the long rainfall series of the reference stations of Bni Slimane (1920–2014) and Djebahia (1923–2014) through the application of three statistical tests (Pettitt, Buishand and Lee and Heghinian) revealed an episode of low rainfall from 1973 to 2001 for the Djebahia station and from 1975 to 2001 for the Bni Slimane station. This period was characterized by a decrease in annual rainfall varying between 14 and 43%, followed by a rainy phase in the watershed with an increase in annual rainfall (35.8%) at the Khebouzia station. The analysis of the kriged maps, developed by geostatistical modeling of the spatial structure of precipitation (1975–2014), supported and corroborated the results of the statistical tests. Indeed, the spatial interpolation based on decadal averages of rainfall from 1975 to 2014 illustrates a well-contrasted spatial variability for the four decades. The northern part of the watershed is characterized by a higher rainfall than the central and southern parts of the watershed. In the light of the results obtained by applying the two approaches mentioned above, a decreasing trend in rainfall is clearly evident from the beginning of the decade 1985–1994. A double rainfall gradient is highlighted with an increase in rainfall from east to west and from north to south. At the same time, there was a surplus towards the end of the third decade and the fourth decade. A return of precipitation is thus highlighted as well as the different breaks in the series. Through this research, the statistical study and the geostatistical mapping have enabled the elaboration of a relevant tool for decision support to the managers in the field of environment and hydraulics, in a general way, and in a context of global warming. In fact, it will allow them to better understand the developments of wadis, the integrated management of water resources in order to guarantee current and future needs for drinking, industrial, and agricultural water in this semi-arid region. [ABSTRACT FROM AUTHOR]

This work focuses on water erosion observed in the northwest region of Algeria. It deals with the specific case of cereals, whose surface status (SS) influences strongly the formation of runoff during the rainy season, due to the formation of slaking crusts. The objective of this work is to study the surface states under different modes of land use, practiced in the region in order to apprehend the contributing areas of runoff and land loss. For this, surface observations were carried out taking into account the spatial organization of SS created by the soil tillage. The surveys are completed at the watershed of the Isser, at a scale of m2 , on six plots sample submitted different cropping systems. These observations were completed by in situ measurements of soil infiltrability. It shows that runoff is closely related to the hydrous and structural state of soil. It decreases from upstream to downstream slopes and is higher on the south-facing slopes than the north-facing ones.

This work focuses on water erosion observed in the northwest region of Algeria. It deals with the specific case of cereals, whose surface status (SS) influences strongly the formation of runoff during the rainy season, due to the formation of slaking crusts. The objective of this work is to study the surface states under different modes of land use, practiced in the region in order to apprehend the contributing areas of runoff and land loss. For this, surface observations were carried out taking into account the spatial organization of SS created by the soil tillage. The surveys are completed at the watershed of the Isser, at a scale of m², on six plots sample submitted different cropping systems. These observations were completed by in situ measurements of soil infiltrability. It shows that runoff is closely related to the hydrous and structural state of soil. It decreases from upstream to downstream slopes and is higher on the south-facing slopes than the north-facing ones. [ABSTRACT FROM AUTHOR]

The drainage basin of Isser, space weakened by the periods of drought and characterized by exposures of marls and very fragile clays, prese nts a high sensitivity to erosion. In addition to the deterioration of the quality of water, the eros ion phenomenon in this zone presents risks of depletion of topsoil, loss of fertility, loosening of plants and pollution by pesticides dissolved in surface water runoff. The erosion results from the conjunction of many pe rmanent factors (as those related to the soil or to the topography), that are evolving o r presenting a random character (such as precipitations) and intervene at different levels i n erosion processes. The purpose of the work is to produce a map of soil vulnerability to the erosion by integrating field data, different thematic maps and satellite images through GIS solution. This map sho uld be a basis for the development of the anti-eros ive land use plan adapted to the specific context of th e drainage basin of Isser. We do integrate four factors which determine the erosion: precipitations , topography, lithology, and vegetation cover. For combining these different factors, we use a cut ting space in regular meshes. The resulting map of the vulnerability to the erosion should reveal homo geneous areas for priority interventions.

En Algérie du Nord, le phénomène d'érosion hydrique présente la forme de dégradation physique des sols la plus importante affectant les reliefs, la production du sol et la stabilité des versants. L’objectif de ce travail est d’évaluer l’influence des contraintes naturelles sur quelques propriétés hydrodynamiques des sols sous différents modes de gestion des terres afin d’appréhender les zones contributives du ruissellement et des pertes en terres au niveau du bassin versant de l’Isser (nord-ouest d’Algérie). Pour réaliser un bon diagnostic des risques de ruissellement et d'érosion sur un versant cultivé, il est nécessaire d'observer le fonctionnement hydrique du terrain au cours de la saison des pluies, ou tout au moins, de tester la capacité d'infiltration des sols soumis à diverses utilisations les plus courantes (Roose, 1996). La mesure de l’infiltrabilité du sol par les méthodes classiques est cependant assez longue et coûteuse. Nous présentons ici le test d'infiltration au cylindre unique sous charge décroissante (surface = 100 cm2) qui est une méthode simple et de faible coût suggérée par Roose et al. en 1993. Ce test permet non seulement de classer les horizons d'une toposéquence en fonction de leur capacité d'infiltration, mais aussi de visualiser le mode de circulation de l'eau d'un horizon aux suivants par comparaison des taches d'humidité créées par l'infiltration. Un exemple sera décrit sur un versant marneux de l’Isser sur sols bruns calcaires argileux. Les mesures sont effectuées à l'échelle du m2, sur un échantillon de six parcelles soumises à différents systèmes de culture. I1 en ressort que l’infiltration est très liée à l’état hydrique et structural du sol. Elle augmente de l’amont vers l’aval des versants et est plus élevée sur les versants exposés nord que ceux exposés sud. [ABSTRACT FROM AUTHOR]

The drainage basin of Isser, space weakened by the periods of drought and characterized by exposures of marls and very fragile clays, presents a high sensitivity to erosion. In addition to the deterioration of the quality of water, the erosion phenomenon in this zone presents risks of depletion of topsoil, loss of fertility, loosening of plants and pollution by pesticides dissolved in surface water runoff. The erosion results from the conjunction of many permanent factors (as those related to the soil or to the topography), that are evolving or presenting a random character (such as precipitations) and intervene at different levels in erosion processes. The purpose of the work is to produce a map of soil vulnerability to the erosion by integrating field data, different thematic maps and satellite images through GIS solution. This map should be a basis for the development of the anti-erosive land use plan adapted to the specific context of the drainage basin of Isser. We do integrate four factors which determine the erosion: precipitations, topography, lithology, and vegetation cover. For combining these different factors, we use a cutting space in regular meshes. The resulting map of the vulnerability to the erosion should reveal homogeneous areas for priority interventions. [ABSTRACT FROM AUTHOR]