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Infiltration is an important part of the hydrological cycle, and it is one of the main abstractions accounted for in the rainfall-runoff modeling. The main purpose of this study is to compare the infiltration models that were used to assess the infiltration rate of the Mitidja Plain in Algeria. Field infiltration tests were conducted at 40 different sites using a double ring infiltrometer. Five statistical comparison criteria including root mean squared error (RMSE), normalized root mean squared error (NRMSE), coefficient of correlation (CC), Nash-Sutcliffe efficiency (NSE), and Kling-Gupta efficiency (KGE) were used to determine the best performing infiltration model and to confirm anomalies between predicted and observed values. Then we evaluated performance of five models (i.e., the Philip model, Kostiakov model, Modified Kostiakov model, Novel model, and Horton model) in simulating the infiltration process based on the adjusted performance parameters cited above. Results indicated that the Novel model had the best simulated water infiltration process in the Mitidja Plain in Algeria. However, the Philip model was the weakest to simulate the infiltration process. The conclusion of this study can be useful for estimating infiltration rate at various sites using a Novel model when measured infiltration data are not available and are useful for planning and managing water resources in the study area.

The objective of this study is to estimate the extreme floods corresponding to different recurrence intervals in Trois Rivières watershed, a large sub-basin of the Macta basin (NW-Algeria). Two regional models are used flow-duration-frequency (Qdf) modelling and gradex method. A methodology for modelling QdF curves based on the so-called continuous converging model has been applied. The second model is gradex method which is a rainfall-runoff probability approach to computing extreme flood discharges in a river. The QdF model gives a complete description of the flood dynamics of Trois Rivières basin. Nevertheless, it is recommended to use this method with vigilance for the predetermination of severe floods for important return periods. However, the gradex method overestimates the extreme floods for different recurrence intervals. This study highlights that diverse methods should be employed for the regional analysis of extreme hydrological events.

Le bassin versant de l'oued Mina, l'un des plus grands sous bassins du Chéliff (Nord-Ouest algérien), est soumis à une forte érosion hydrique, les sédiments érodés et transportés par l'oued se déposent à l'aval dans le barrage de Sidi M'Hamed Ben Aouda.

In this study, a statistical analysis of historical and projected values of the annual, seasonal, and supra-seasonal precipitation concentration index (PCI) was conducted for different stations in the Cheliff watershed. Statistical methods such as breakpoint and trend analysis using Pettitt and Mann–Kendall tests were used for the PCI values of annual, monthly, and supra-seasonal precipitation data between 1950 and 2014. The PCI values varied between 14.24% and 24.86% annually, between 10.75% and 18.74% seasonally, and between 11.23% and 26.98% supra-seasonally. According to the Pettitt and Mann–Kendall tests, there was an insignificant change in precipitation distribution during the study period. Spatial analysis using the inverse distance weighting (IDW) method confirmed the minor variability in precipitation distribution in the study area. The Pearson correlation coefficient between oscillation indices and PCI values at different scales showed significant values with the Mediterranean Oscillation index (MOi), North Atlantic Oscillation (NAO), and Western Mediterranean Oscillation index (WeMOi), highlighting their potential influence on annual PCI values. For the climate projection scenarios, projected PCI values align with historical PCI values. Application of Pettitt and Mann-Kendall tests to the projected PCI series shows that there will not be a significant change in future precipitation distribution.

Le bassin versant de l'oued Mina, l'un des plus grands sous bassins du Chéliff (Nord-Ouest algérien), est soumis à une forte érosion hydrique, les sédiments érodés et transportés par l'oued se déposent à l'aval dans le barrage de Sidi M'Hamed Ben Aouda.Les données acquises durant les campagnes de prélèvements de 1971 à 2002 aux stations hydrométriques, hauteurs d'eau, concentrations en matières en suspension_(MES) et débits solides, utilisées pour la quantification du transport solide, ont été analysées pour décrire les cycles saisonniers et la variabilité interannuelle.L'analyse des écoulements, à la station d'oued El Abtal, montre que les débits varient de 40,7 m3.s-1, en 1974, à 0,48 m3.s-1en 1997, soit une variabilité supérieure à 95 %.Le taux d'abrasion du bassin de l'oued Mina, pendant la période d'étude, a été évalué à 211 t.km2.an-1, cette valeur reste relativement faible par rapport à celles trouvées pour d'autres régions à régime hydrologique similaire, et la valeur de concentration moyenne sur la même période a été évaluée à plus de 34 g.l-1dans le sous bassin contrôlé par la station de Sidi Aek Djilali et de plus de 12 g.l-1dans le sous bassin contrôlé par la station d'oued El Abtal.

Algeria is periodically affected by severe and repeated flooding. Flood hazard studies require the estimation of extreme flood flows. To predict and estimate the characteristics of maximum flows, knowledge of their distribution law is essential. The L-moments method was used to determine homogeneous regions and the appropriate distribution for these regions. Three homogeneous regions were delineated. This technique produced a Pearson type III distribution for the coastal region and the Tell Atlas and a Pareto distribution for the steppe regions and high plateaus of Eastern and Western Algeria. To estimate maximum flow at ungauged sites for different return periods, the 'index-flood' method was used. An empirical formula was developed that uses the average annual maximum flow as a function of catchment area and the average slope of the main channel to estimate maximum flow at any point on the Oued. The coefficient of determination and the Nash criterion, for the three regions, are superiors to 88% and 83% respectively. The root mean squared error, for the three regions, is less than 12%. These values show the robustness of the developed models.

The sediment transport is a complex phenomenon by its intermittent nature, randomness and by its spatiotemporal discontinuity. By reason of its scale, it constitutes a major constraint for development; it decreases storage capacity of dams and degrades state of ancillary structures.

The watershed of the studied region, part of the large basin of Macta situated in the north-west of Algeria, is submitted to flash floods and is particularly dangerous. Facing to the recurring of those catastrophic events, the understanding of hydrologic process constitutes a strategic axis of prevention against floods. Functioning indicators of the basin have been searched for by modelling of the flow on different floods observed at level of the stations established along Mekkera wadi. Among hydrologic models, the Muskingum model has been chosen for floods propagation study and estimations of flows, and the QdF model is used to evaluate the extreme quintiles and build the hydrographs of different return periods. The floods episodes observed at level of stations of Sidi Ali Benyoub and of Sidi Bel Abbès are characterised by importance of damages caused. The town of Sidi Bel Abbès built in the major bed of Mekkera and so the communes situated in the plains are the most exposed to these sudden floods.

The aim of this paper is to study the possibility to use the generalised extreme value (GEV) distribution by adjusting the three parameters for 65 rainfall stations located in steppe region of western Algeria. Analysis of maximum daily rainfall with Gumbel model, which traditionally used shows that it is not perfectly suited to steppe region of western Algeria. In fact, the small hydrological sample sizes generally available affect remarkably the estimation of parameters and leads to underestimate the frequency of that value. Therefore, it opts for the hypothesis that maximum daily rainfalls in the study region are distributed according to GEV distributions but kis a regional constant to be determined. A value of k= –0.053 is an acceptable hypothesis in relation to the uncertainties on the local estimates. This value of kallows also in finding an observations number in agreement with the estimated return periods.

Abstract: In Northern Algeria, the Cheliff watershed has been severely affected by a decline in runoff since the 1970s due to a decrease in rainfall. However, the sensitivity of watersheds to this decline is variable and involves complex processes. This basin contains several dams that supply the population with water for drinking as well as for irrigation purposes to ensure a good agricultural yield necessary for food security of more than 5 million inhabitants. Rational and optimal management becomes an absolute necessity in new climatic conditions. It will be done based on efficient modelling tools. The development of high-performance models is more than necessary for a better assessment of potential and risks in the short, medium and long term, to adopt an efficient strategy in the water sector which have to be in line with ground reality. To do this, the soil and water assessment tool (SWAT) is a very reliable way to simulate the hydrological behaviour of the region. In this study, the SWAT model was applied to five dam-feeding basins in the Cheliff basin and its outlet on a monthly scale. The results obtained are very satisfactory with R2values ranging from 0.69 to 0.79, Nash–Sutcliffe efficiency coefficient between 0.68 and 0.78 and bias percentage between −21% and −1.5%. The Oued Cheliff hydrogram modelled by the SWAT at the Sidi Belattar station (basin outlet) showed that surface flow represents 58.3% and 37.3% lateral flow and 4.4% that feeds deep aquifers. The models developed will be used as decision-making tools by water-resource managers. Research highlights:

In northern Algeria, the Cheliff basin is strongly affected by a decline in runoff since the 1970s.

The sensitivity of watersheds to this decline is variable and involves complex processes: hydrological systems, climate change and solid transport.

We have used meteorological data, DEM, land use and land cover of the study region.

Application of the SWAT model in the Cheliff basin.

The reliability tests used show that the model output results for calibration and validation are satisfactory in studied dams and outlets.

Presence of karsts slightly affects the performance of the model.

The results serve as a decision support tool.

Groundwater is a very widely used resource in the Cheliff-Zahrez watershed. However, following the drought in the basin, farmers of the region has resorted to the intense mobilization of groundwater resources. This work allowed us to study the impact of rainfall reduction on groundwater resources in the basin, by studying groundwater and natural infiltration. We have considered the future scenarios to estimate rainfall for 2025 and 2050 and therefore the (groundwater) recharge at those time horizons.

The Beni-Chougrane mountains (West of Algeria) are submitted to an intense activity of erosion. This phenomenon has provoked the agricultural ground degradation and the siltation of Fergoug reservoir. To study and understand the phenomenon in this region, the National Institute of Forest Researches of Mascara has established an experimental station (cf. Wischmeir 1968). Thus experiences have been led on two characteristic local soil types: a Chalky brown ground on 20 % on sandstone slopes and brown vertisol on 45 % clayey - marl slopes. Taking the totality of data (4 campaigns measures) we have shown that the rain, the runoff and the state of humidity of the ground can not explain correctly to them alone and separately the variance of the erosion phenomenon. On the other hand, the grouped in data by season gives best relationships between the specific degradation and explanatory factors, as well as relationships between the depth of runoff, the rain and the state of humidity of the ground. In hot seasons energy provoked by the rain is relatively important than the energy provoked by runoff. While in cold seasons energy of the runoff is more important than the energy provoked by the rain.

This work is a study of solid transportation and volumes of rising water and base water at different scales in the Oued Ebda catchment (Ebda's river - North of Algeria). Indeed the National Dams Agency plans to build a dam at the level of this side basin. By the present work it was demonstrated the great effect of erosion on Oued Ebda catchment (1875t/km2/an) and the alluviation danger on the future dam. This work has also allowed to give some requirements to struggle against erosion phenomenon and to protect the future dam against alluviation.

Drought is the most frequent natural disaster in Algeria during the last century, with a severity ranging over the territory and causing enormous damages to agriculture and economy, especially in the north-west region of Algeria. The above issue motivated this study, which is aimed to analyse and predict droughts using the Standardized Precipitation Index (SPI). The analysis is based on monthly rainfall data collected during the period from 1960 to 2010 in seven plains located in the north-western Algeria. While a drought forecast with 2 months lead-time is addressed using an artificial neural network (ANN) model. Based on SPI values at different time scales (3-, 6-, 9-, and 12-months), the seven plains of north-western Algeria are severely affected by drought, conversely of the eastern part of the country, wherein drought phenomena are decreased in both duration and severity. The analysis also shows that the drought frequency changes according to the time scale. Moreover, the temporal analysis, without considering the autocorrelation effect on change point and monotonic trends of SPI series, depicts a negative trend with asynchronous in change-point timing. However, this becomes less significant at 3 and 6 months’ time scales if time series are modelled using the corrected and unbiased trend-free-pre-whitening (TFPWcu) approach. As regards the ANN-based drought forecast in the seven plains with 2 months of lead time, the multi-layer perceptron networks architecture with Levenberg–Marquardt calibration algorithm provides satisfactory results with the adjusted coefficient of determination (Radj2) higher than 0.81 and the root-mean-square-error (RMSE) and the mean absolute error (MAE) less than 0.41 and 0.23, respectively. Therefore, the proposed ANN-based drought forecast model can be conveniently adopted to establish with 2 months ahead adequate irrigation schedules in case of water stress and for optimizing agricultural production.