Combined analysis of temperature and rainfall variability as they relate to climate indices in Northern Algeria over the 1972–2013 period

Zeroual, Ayoub; Assani, Ali A.; Meddi, Mohamed

doi:10.2166/nh.2016.244

Cited by 59 publications

(25 citation statements)

References 37 publications

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“…The results of the MK test presented by Table 10 on the annual time scale at different levels of statistical significance (p = 0.01, 0.05 and 0.1)shows no statistically significant trend for all the rainfall stations, which is similar to the results of the other study by Zeroual et al [14]. Monthly rainfall has statistically significant increasing trends for Sebdou, Khemis, Beni Bahdel, Merbeh, Ouled Mimoun, Sidi Benkhala, Chouly, and Hennaya stations.…”

Section: Trend Analysissupporting

confidence: 85%

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Analyzing Trend and Variability of Rainfall in The Tafna Basin (Northwestern Algeria)

et al. 2020

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Northwest Algeria has experienced fluctuations in rainfall between the two decades 1940s and 1990s from positive to negative anomalies, which reflected a significant decline in rainfall during the mid-1970s. Therefore, further analyzing rainfall in this region is required for improving the strategies on water resource management. In this study, we complement previous studies by dealing with sub basins that were not previously addressed in Tafna basin (our study area located in Northwest Algeria), and by including additional statistical methods (Kruskal–Wallis test, Jonckheere-Terpstra test, and the Friedman test) that were not earlier reported on the large scale (Northwest Algeria). In order to analyse the homogeneity, trends, and stationarity in rainfall time series for nine rainfall stations over the period 1979–2011, we have used several statistical tests. The results showed an increasing trend for annual rainfall after the break detected in 2007 for Djbel Chouachi, Ouled Mimoun, Sidi Benkhala stations using Hubert, Pettitt, and Buishand tests. The Lee and Heghinian test has detected a break at the same year in 2007 for all stations except Sebdou, Beni Bahdel, and Hennaya stations, which have a break date in 1980. We have confirmed this increasing trend for rainfall with other trend detection methods such as Mann Kendall and Sen’s method that highlighted an upward trend for all the stations in the autumn season, which is mainly due to an increase in rainfall in September and October. On a monthly scale, the date of rupture is different from one station to another because the time series are not homogeneous. In addition, we have applied three tests enabling further results: (i) the Jonckheere-Terpstra test has detected an upward trend for two stations (Khemis and Hennaya), (ii) Friedman test has indicated the difference between the mean rank again with Khemis and Hennaya stations and the Merbeh station, (iii) according to the Kruskal-Wallis test, there have been no variance detected between all the rainfall stations. The increasing trend in rainfall may lead to a rise in stream flow and enhance potential floods risks in low-lying regions of the study area.

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Section: Trend Analysissupporting

confidence: 85%

“…This also coincides with a proven negative correlation indicated between the temperature and the climate index WeMO (Western Mediterranean Oscillation) in the Western Mediterranean region. This decrease in rainfall has been identified since the mid-1970s [11][12][13][14].…”

Section: Introductionmentioning

confidence: 80%

Analyzing Trend and Variability of Rainfall in The Tafna Basin (Northwestern Algeria)

et al. 2020

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“…Change can be attributed to climate change (Zhang and Nearing, 2005;Ziadat and Taimeh, 2013;Liu et al, 2014;Achite and Ouillon 2016) or anthropogenic actions (Cerdà, 1998a(Cerdà, , 1998bLiu et al, 2014), such as intensification of agriculture (Montgomery, 2007;Lieskovský and Kenderessy, 2013), deforestation (Walling, 2006), forest fires (González-Pelayo et al, 2006;Cerdà et al 2010) or urbanization (Graham et al, 2007;Whitney et al, 2015). In the study area, and like North Africa and the Maghreb, there has been a continuous drought since the mid-1970s (Giorgi and Lionello, 2008;Achite and Ouillon, 2016;Zeroual et al, 2016). Overall, decreasing rainfall is more concentrated over time (Ghenim and Megnounif, 2016), which increases the susceptibility of soils to erosion (Shakesby et al, 2002;Achite and 5 Ouillon, 2007;Bates et al, 2008;Vachtman et al, 2012).…”

Section: Recurrence Interval Of the Effective Discharge 15mentioning

confidence: 99%

How to determine the effective discharge and its return period in a semi-arid basin? The case of the Wadi Sebdou, Algeria (1973–2004)

Megnounif

Ouillon

2018

Preprint

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around 9700 words against 10700 in the previous version). 3. The section title 'study area' was changed to 'study area and data collection'. Its text was rewritten from former sections 2 and 3.3 (in reply to referee #1's suggestion). A figure representing the watershed position was included. 5 4. Section 3 was fully revised according to the new thread. Subsection 3.3 was separated into three subparts, two of which moved to the introduction and to the revised section 2. Other subsections of section 3 are now based on the mean approach, the analytical approach, the half-load discharge and the return periods.5. The recurrence interval of a certain discharge like the effective discharge is traditionally calculated in 10 hydrology. However, this return period is only based on hydrologic distributions (from the distributions of mean and maximum discharge). We propose in this paper something more original, calculating a recurrence interval of the effective discharge compared to the distribution of annual half-load discharge, which was obtained from both water and sediment data time series, and investigate its additional information. The text was clarified accordingly. 15 6. Figure 3 was redrawn in semi-log scale.7. The comparison of the two calculations makes it possible to add information on the limits of the analytical method (based on a probability density function for the flow frequency). It did not provide good results in semi-arid environments because the sediment rating curve introduces errors (designed as 'of the first type' in the paper) and because pronounced asymmetric probability distributions failed to 20 reproduce good frequencies of high discharge (errors 'of second type'). Consequently, this comparison shows that the mean method by decomposition of histogram classes is the most suitable in a semiarid environment. This had never been tested in the literature. It's an original result. This was emphasized in subsection 5.4. 8. To be consistent all along the paper with the subsection "Elementary contributions and budgets", QY50 25 (i.e. the water discharge that delimits 50% of the cumulative sediment yield) was preferred to QY1/2 in the revised version of the paper. 4 Replies by the authorsThe paper is interesting and well within the scope of the journal, nevertheless it needs to be reinforced with reference to several points, mainly regarding paper clarity and organization.Reply: Thanks for the general comment and all your suggestions to makes the paper better organized and 5 clearer.The title should more informative and let the reader know that it deals with sediment transport and hydrological implications. Reply:We propose a new title: "Mean and analytical methods to characterize the efficiency of floods to move sediments in a small semi-arid basin". The mean method refers to the use of histograms where each 10 class of discharge is represented by its mean value, and the analytical method in which the dominant discharge is defined as the solution of h'(Q)=0 where h(Q)= f(Q).g(Q), f(Q) being a probability ...

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“…Biedenharn et al (2001) suggest to carefully study long (over 30 years) data series (liquid flow, sediment concentration and flow frequency) and to ensure that the hydrological regime of the watershed did not undergo a significant change in flow rates or sediment production in the long term. Change can be attributed to climate change (Zhang and Nearing, 2005;Ziadat and Taimeh, 2013;Liu et al, 2014;Achite and Ouillon, 2016) or anthropogenic actions (Cerdà, 1998a, b;Liu et al, 2014), such as intensification of agriculture (Montgomery, 2007;Lieskovský and Kenderessy, 2014), deforestation (Walling, 2006), forest fires (González-Pelayo et al, 2006;Cerdà et al, 2010) or urbanization (Graham et al, 2007;Whitney et al, 2015). In the study area, and like northern Africa and the Maghreb, there has been a continuous drought since the mid-1970s (Giorgi and Lionello, 2008;Achite and Ouillon, 2016;Zeroual et al, 2016).…”

Section: Limits To the Application Of The Analytical Solution In Semimentioning

confidence: 99%

Empirical and analytical methods to characterize the efficiency of floods to move sediment in a small semi-arid basin

Megnounif

Ouillon

2018

Hydrol. Earth Syst. Sci.

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Over a long multi-year period, flood events can be classified according to their effectiveness in moving sediments. Efficiency depends both on the magnitude and frequency with which events occur. The effective (or dominant) discharge is the water discharge which corresponds to the maximum sediment supply. If its calculation is well documented in temperate or humid climates and large basins, it is much more difficult in small and semi-arid basins in which short floods with high sediment supplies occur. Using the example of 31 years of measurements in the Wadi Sebdou (north-west Algeria), this paper compares the two main statistical approaches to calculate the effective discharge (the empirical method based on histograms of sediment supply by discharge classes and an analytical calculation based on a hydrological probability distribution and on a sediment rating curve) to a very simple proxy: the half-load discharge, i.e. the flow rate corresponding to 50 % of the cumulative sediment yield. Three types of discharge subdivisions were tested. In the empirical approach, two subdivisions provided effective discharge close to the half-load discharge. Analytical solutions based on log-normal and log-Gumbel probability distributions were assessed but they highly underestimated the effective discharge, whatever the subdivision used to adjust the flow frequency distribution. Furthermore, annual series of maximum discharge and half-load discharge enabled the return period of hydrological years with discharge higher than the effective discharge (around 2 years) to be inferred and showed that more than half of the yearly sediment supply is carried by flows higher than the effective discharge only every 7 hydrological years. This study was the first to adapt the analytical approach in a semi-arid basin and to show the potentiality and limits of each method in a such climate.

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Combined analysis of temperature and rainfall variability as they relate to climate indices in Northern Algeria over the 1972–2013 period

Cited by 59 publications

References 37 publications

Analyzing Trend and Variability of Rainfall in The Tafna Basin (Northwestern Algeria)

Analyzing Trend and Variability of Rainfall in The Tafna Basin (Northwestern Algeria)

How to determine the effective discharge and its return period in a semi-arid basin? The case of the Wadi Sebdou, Algeria (1973–2004)

Empirical and analytical methods to characterize the efficiency of floods to move sediment in a small semi-arid basin

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