Abdesselam Megnounif - Academia.edu (original) (raw)

Papers by Abdesselam Megnounif

Polish Journal of Environmental Studies, Jun 19, 2024

The study aims to establish a graphical relationship between sediment concentration (C) and water... more The study aims to establish a graphical relationship between sediment concentration (C) and water discharge (Q) during flood events in the Isser catchment. Hysteresis, indicating a time lag between discharge flow (Q) and suspended sediment concentration (SSC) curves, varies based on sediment availability, event magnitude, and sequence. Based on the 2026 data pairs of water discharge and suspended sediment concentration (Q-SSC), we have selected 22 flood events. The most frequent hysteresis loops were complex (10 loops), with 08 clockwise loops, 02 figure-eight loops, and 02 anticlockwise loops. Complex hysteresis loops accounted for 63% of solid loads and 37% of water discharge loads, while 50% of total water yield and 23% of total sediment yield were associated with clockwise loops. Principal Component Analysis (PCA) revealed that water discharge load, mean concentration, maximum concentration, and concentration at the flow discharge peak are key variables influencing hysteresis patterns.

Hydrological Sciences Journal-journal Des Sciences Hydrologiques, Dec 1, 2007

HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Distributed under a Creative Commons Attribution-NonCommercial 4.0 International License

Revue LJEE, Mar 16, 2015

Dans ce travail, on s'intéresse à l'origine des sédiments transportés en suspension par le cours ... more Dans ce travail, on s'intéresse à l'origine des sédiments transportés en suspension par le cours d'eau, l'Oued Sebdou de la Haute-Tafna. Cependant, il est connu que les sédiments ramenés par le cours d'eau sont produits soit par ruissellement superficiel sur les versants soit arrachés du lit et des berges du cours d'eau. Dans le but de quantifier la contribution de ces deux mécanismes d'érosion dans la production des sédiments dans le bassin versant de la Haute-Tafna, on analyse la variabilité de la charge en suspension de l'eau quant aux fluctuations des débits d'écoulement. L'étude par l'utilisation de la décomposition des hydrogrammes de crues, pour la période allant de septembre 1988 à août 1993, révèle que la contribution du ruissellement dans la production des sédiments est importante en automne, alors qu'au printemps, c'est l'érosion du réseau hydrographique qui est importante. En été, la charge solide produite sur les versants suite aux violents orages qui caractérisent la région constitue la quasi-totalité de la matière solide transportée par le cours d'eau.

Sustainability

Water infrastructure management relies on information, communication strategies, and affordable t... more Water infrastructure management relies on information, communication strategies, and affordable technologies. This paper used demand analysis and modeling to guide strategic decision-making in sustainable water management for the urban cluster in Tlemcen, Algeria. To achieve this, the water supply and demand of the study area were assessed over the past three decades. The Water Evaluation and Planning (WEAP) system was employed considering different future scenarios to help decision-makers consider the best choices for sustainable urban water resources management. The results showed that the average water production and distribution efficiency was only 46% due to the high network loss. Therefore, urgent action should be considered to increase the efficiency of the distribution network. Moreover, the outcome showed severe unmet demand in 2050, which can be managed by improving the water networks, increasing conventional water production, and reducing personal water consumption. In co...

Meteorology, Hydrology and Water Management, Jun 24, 2019

A three decade-long study on the variability of drought in relation to the contribution of rainfa... more A three decade-long study on the variability of drought in relation to the contribution of rainfall was conducted at the Wadi Mekerra watershed, located in northwest Algeria, covering the period from 1973 to 2005. The runoff and rainfall data were analyzed using the Mann-Kendall test, the double mass curve method and the SPI index. A rupture of the studied series appeared during the 1980s. The rainfall and runoff trends and contributions were in general, sharply reduced. The region experienced extreme drought between 1981 and1989, and between 1993 and 2001, rainfall contributions were greater than 60%. This increase, which was recorded in August, September and October for all the parameters studied, shows the importance of the superficial runoff component when combined with decreased infiltration. These climatic conditions reduce the natural recharging of groundwater, and cause an increased susceptibility to soil erosion, reduced agricultural production and an increased risk of floods.

Hydrology and Earth System Sciences, Dec 6, 2018

Journal of Hydrology, Aug 1, 2013

Small sub-basins are numerous in Mediterranean area and global sedimentary budgets cannot be obta... more Small sub-basins are numerous in Mediterranean area and global sedimentary budgets cannot be obtained without a detailed understanding of the hydroclimatic processes that govern sediment fluxes in these small river systems. In this study, the shape of the relationship between sediment concentration (C) and water discharge (Q) during flood events of a 31-years period (1973-2004) was analyzed at the outlet of the Wadi Sebdou basin (256 km 2) in northwest Algeria, using a new graphical analysis method based on features of hysteresis loops. Each flood was decomposed as successive stages-each of which being characterized by a sediment rating curve-and used to quantify the contribution of diverse sediment sources within the basin. Seven common classes of hydrological events (single valued and six hysteresis loops: clockwise, counterclockwise , eight-shaped, single valued plus one loop, either clockwise or counterclockwise , and single valued plus at least two loops) were explored. Sediment supply from locally derived sources (or ''base load'') was high and reached 77% of total sediment yield for the study period, and was attributed to weathering of bed material or gullies. The remainder portion was derived from hill-slopes, re-suspension of fresh fine deposits in the river bed, or bank collapse. The ratio of suspended sediment load derived from active sediment source varies considerably from one flood to another depending on many factors, such as seasonality and antecedent type of flood. The simpler floods were the most frequent ones but produced less sediment. The most frequent floods were clockwise or anticlockwise (52% of floods) but brought only 34% of the total sediment flux. The 18% of the most complex floods (single valued plus at least two loops) produced more than 53% of the sediments, mainly supplied by base load (84%). Intra-annual variability was very high. Over 31-years, the five biggest floods cumulated 64% of the total sediment flux and were of three classes, the most complex floods being dominant. The largest contribution occurred during one single 33-days long hydrological event with complex form which represented 26% of the total sediment flux. Apart from the five biggest flood events, the base load represented 53%. The biggest floods favour base load as compared to the smallest ones.

Journal of Water and Land Development, Sep 1, 2018

A-study design B-data collection C-statistical analysis D-data interpretation E-manuscript prepar... more A-study design B-data collection C-statistical analysis D-data interpretation E-manuscript preparation F-literature search

Le Journal de l'Eau et de l'Environnement, Oct 16, 2006

Sciences & Technologie, Dec 1, 1999

L'utilisation des lois de distribution en climatologie aide non seulement à résoudre un certain n... more L'utilisation des lois de distribution en climatologie aide non seulement à résoudre un certain nombre de problèmes d'ordre numérique (modèles de représentation et calcul des valeurs caractéristiques), mais aussi à décrire et expliquer certains phénomènes. Dans la présente étude , nous avons essayé de mettre en évidence l'influence d'une chaîne montagneuse (Monts de Tlemcen), considérée comme barrière pluviométrique, par les modèles de distribution statistiques d'une chronologie de données pluviométriques mesurées dans cinq stations différentes, trois en plein montagnes, les deux autres de part et d'autre, respectivement sur l'Ubac et l'Adret.

Arabian Journal of Geosciences, Dec 1, 2022

Journal of Water Science, Apr 12, 2005

The extent and rates of alluvial deposit and dam siltation caused by sédiment déposition from Mag... more The extent and rates of alluvial deposit and dam siltation caused by sédiment déposition from Maghreb streams hâve prompted a number of attempts to quantify and explain the complex mechanisms of suspended sédiment transport. In Algeria, a country with scarce water resources, déposition of sédiments in dams is estimated to average 20 million m 3 /year, which contributes to a 0.3% yearly loss of storage capacity from a total capacity estimated at 6.2 billion m 3. Of interest in this context are suspended sédiment loads in Mediterranean Algeria's Mouilah River, on which is built the Hammam Boughrara, a 117 million m 3 capacity dam put into service in 1998.

Sécheresse, Apr 1, 2013

Dans ce travail, en se basant sur les donnees mensuelles issues de 16 postes pluviometriques situ... more Dans ce travail, en se basant sur les donnees mensuelles issues de 16 postes pluviometriques situes dans le bassin-versant de la Tafna, on se propose d’examiner les principaux changements qui ont affecte le regime des pluies. La procedure de segmentation de Hubert a permis de mettre en evidence une cassure d’homogeneite localisee principalement entre le milieu et la fin des annees 1970. A part une occurrence accentuee d’annees seches et l’apparition de secheresses aigues, la saisonnalite et la concentration des pluies n’ont pas change. On note meme une reduction de l’agressivite des precipitations pendant la periode seche.

International Journal of Geophysics, 2016

The daily rainfall dataset of 35 weather stations covering the north of Algeria was studied for a... more The daily rainfall dataset of 35 weather stations covering the north of Algeria was studied for a period up to 43 years, recorded after 1970s. The variability and trends in annual maximum daily rainfall (AMDR) time series and their contributions in annual rainfall (AR) were investigated. The analysis of the series was based on statistical characteristics, Burn's seasonality procedure, Mann-Kendall test, and linear regression technique. The contribution of the AMDR to AR analysis was subjected to both the Buishand test and the double mass curve technique. The AMDR characteristics reveal a strong temporal irregularity and have a wide frequency of occurrence in the months of November and December while the maximum intensity occurred in October. The observed phenomenon was so irregular that there was no dominant season and the occurrence of extreme event can arrive at any time of the year. The AMDR trends showed that only six of 35 stations have significant trend. For other stations, no clear trend was highlighted. This result was confirmed by the linear regression procedure. On the contrary, the contribution of AMDR in annual totals exhibited a significant increasing trend for 57% of the sites studied with a growth rate of up to 50%.

LARHYSS Journal, Jun 21, 2016

In this study, the spatial and temporal patterns of rainfall concentration on daily and monthly s... more In this study, the spatial and temporal patterns of rainfall concentration on daily and monthly scale were investigated in the Kebir-Rhumel watershed located in the northeast of Algeria. Based daily rainfall dataset between 1968 and 2013 of 20 weather stations, two indices were used in the study: the Precipitation Concentration Index (PCI) and the Concentration Index (CI), for measuring seasonality and daily heterogeneity of rainfall. In addition, the trends of annual rainfall, PCI and CI were tested by the Mann-Kendall method. The results show a disparity in rainfall amounts between norths sufficiently watered with a significant decrease in southbound. The values of the concentration (for daily and monthly scales) seem generally inversely proportional to the rainfall amounts. The concentration in the watershed is seasonal with a tendency towards the irregularity. The positive trends in annual precipitation, PCI and CI were found in most stations, although the trends were only very little statistically significant.

Revue Nature et Technologie, Jun 30, 2013

La relation en puissance issue de la re-transformation logarithmique entre le débit et la concent... more La relation en puissance issue de la re-transformation logarithmique entre le débit et la concentration des sédiments en suspension est largement utilisée pour caractériser la dynamique sédimentaire des cours d'eau et pour estimer l'apport solide en suspension pour des bassins versants non jaugés. Cette relation présente une erreur ou biais lié principalement à la transformation de l'échelle logarithmique à l'échelle arithmétique. Ce biais se traduit généralement par une sous-estimation de l'apport solide en suspension. Le présent travail teste la précision de cette relation en adoptant plusieurs procédures durant une période de 13 années hydrologiques (1985-86 à 1997-98) dans le bassin versant de l'Oued Sebdou. Malgré que l'erreur dans l'estimation de l'apport solide annuel soit parfois importante entre-46,96% et +51,22%, quelques procédures permettent d'estimer cet apport à des taux d'erreur très faibles. La subdivision de la série des débits et des concentrations en classes semble donner la relation la plus exacte vis-à-vis de l'estimation de l'apport solide en suspension.

Arabian Journal of Geosciences, Mar 28, 2016

The impact of changes in rainfall can be studied by means of the sediment transport in the rivers... more The impact of changes in rainfall can be studied by means of the sediment transport in the rivers. The link between rainfall irregularity and sediment rating parameters was investigated in the Wadi Sebdou watershed of 256 km 2 located in northwest Algeria. The data set includes rainfall records and cover the period from September 1939 to August 2009. Hydrometric records consist of instantaneous measurements flow discharge, Q, and suspended sediment concentration, C, based on a monitoring program from September 1973 to August 2003. In neighboring gauging stations, the periods of record were either short or discontinuous and may not be representative to assess the potential causes of the suspended-sediment changes. The time evolution of sediment rating parameters was used to improve understanding of the interaction between sediment delivery supplied from internal and external sources to the wadi channel. Our findings indicate that the rating parameters varied by many orders of magnitude, suggesting significant temporal change in both potential of sediment yield and sediment sources. High bparameter (≅1.12) and low a-parameter values (≅0.018) were observed during the time interval of change from wet to dry period occurred in the mid of 1970s. The growth of vegetation and the well-developed organic soil horizons have reduced runoff and prevented particle detachment and transport. So, the functioning of sediment sources external to the channel was comparable to that of temperate regions. After that transition, the prolonged dryness has led to a higher risk of desertification and critical soil erosion. Therefore, the functioning of sediment sources external to the wadi-flow becomes similar to that observed in arid river systems, while the fluctuation of sediment contribution supplied from hydrographic network suggests a watershed functioning as semi-arid streams. The watershed ability to sediment yield was high toward the mid of the dry period and sediment delivery supplied from sources both internal and external to the wadi channel was copious suggesting a large amount of stored sediment at the beginning of a runoff season and an increased transport capacity of the river.

A large variety of hysteresis shapes is observed in the suspended-sediment concentration-discharg... more A large variety of hysteresis shapes is observed in the suspended-sediment concentration-discharge relationship. The analysis of such forms encompasses two main axes; a qualitative classification a...