Regional flood frequency analysis in the High Atlas mountainous catchments of Morocco

Zkhiri, Wiam; Tramblay, Yves; Hanich, Lahoucine; Berjamy, Brahim

doi:10.1007/s11069-016-2723-0

Cited by 23 publications

(11 citation statements)

References 31 publications

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“…A split-sample procedure has been implemented to validate the choice of the distribution. The same procedure as described in Zkhiri et al (2017) and Renard et al (2013) is retained based on a bootstrap cross-validation. The relative average root-mean-square error (RMSE) for the validation samples is used as an evaluation metric to select the best distribution.…”

Section: Distribution Fittingmentioning

confidence: 99%

Impact of the dry-day definition on Mediterranean extreme dry-spell analysis

Rivoire

Tramblay

Neppel

et al. 2019

Nat. Hazards Earth Syst. Sci.

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Abstract. To define a dry day, the most common approach is to identify a fixed threshold below which precipitation is considered equivalent to zero. This fixed threshold is usually set to account for measurement errors and precipitation losses due to the atmospheric evaporation demand. Yet, this threshold could vary in time according to the seasonal cycle and in the context of long-term trends, such as the increase in temperature due to climate change. In this study, we compare extreme dry spells, defined either with a fixed threshold for a dry day (1 mm) or with a time-varying threshold estimated from reference evapotranspiration (ET0), for a large database of 160 rain gauges covering large parts of the Mediterranean basin. Results indicated positive trends in ET0 during summer months (June, July and August) in particular. However, these trends do not imply longer dry spells since the daily precipitation intensities remain higher than the increase in the evaporative demand. Results also indicated a seasonal behavior: in winter the distribution of extreme dry spells is similar when considering a fixed threshold (1 mm) or a time-varying threshold defined with ET0. However, during summer, the extreme dry-spell durations estimated with a 1 mm threshold are strongly underestimated in comparison to extreme dry spells computed with ET0. We stress the need to account for the atmospheric evaporative demand instead of using fixed thresholds for defining a dry day when analyzing dry spells, with respect to agricultural impacts in particular.

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Section: Distribution Fittingmentioning

confidence: 99%

Impact of the dry-day definition on Mediterranean extreme dry-spell analysis

Rivoire

Tramblay

Neppel

et al. 2019

Nat. Hazards Earth Syst. Sci.

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“…On average, 60% of the annual discharge occurs between March and May [8] (Figure 2). However, the hydrological regime is also influenced by the high annual variability in the snowfall amount and melt-out date [6,9,24].…”

Section: Study Areamentioning

confidence: 99%

Variations of the Snow Water Equivalent in the Ourika Catchment (Morocco) over 2000–2018 Using Downscaled MERRA-2 Data

Baba

Gascoin

Jarlan

et al. 2018

Water

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The Ourika River is an important tributary of the Tensift River in the water-stressed region of Marrakesh (Morocco). The Ourika river flow is dominated by the snow melt contribution from the High Atlas mountains. Despite its importance in terms of water resources, the snow water equivalent (SWE) is poorly monitored in the Ourika catchment. Here, we used MERRA-2 data to run a distributed energy-balance snowpack model (SnowModel) over 2000–2018. MERRA-2 data were downscaled to 250-m spatial resolution using a digital elevation model. The model outputs were compared to in situ measurements of snow depth, precipitation, river flow and remote sensing observations of the snow cover area from MODIS. The results indicate that the model provides an overall acceptable representation of the snow cover dynamics given the coarse resolution of the MERRA-2 forcing. Then, we used the model output to analyze the spatio-temporal variations of the SWE in the Ourika catchment for the first time. We suggest that MERRA-2 data, which are routinely available with a delay of a few weeks, can provide valuable information to monitor the snow resource in high mountain areas without in situ measurements.

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“…The contribution of snow melt to their mean annual discharge was estimated to range from 15% to 45% (Boudhar et al, ). However, this contribution is probably more important from a water resource management perspective because (i) the annual flood due to snow melt occurs at this period of the year when irrigation is crucial to the crop growth and (ii) the melt water flood is more stable and easier to use than the flash floods triggered by heavy rainfalls, which often cause more harm than good in this region (Zkhiri et al, ).…”

Section: Introductionmentioning

confidence: 99%

Effect of Digital Elevation Model Resolution on the Simulation of the Snow Cover Evolution in the High Atlas

Baba

Gascoin

Kinnard

et al. 2019

Water Resources Research

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The snow melt from the High Atlas represents a crucial water resource for crop irrigation in the semiarid regions of Morocco. Recent studies have used assimilation of snow cover area data from high‐resolution optical sensors to compute the snow water equivalent and snow melt in other mountain regions. These techniques however require large model ensembles, and therefore it is a challenge to determine the adequate model resolution that yields accurate results with reasonable computation time. Here we study the sensitivity of an energy balance model to the resolution of the model grid for a pilot catchment in the High Atlas. We used a time series of 8‐m resolution snow cover area maps with an average revisit time of 7.5 days to evaluate the model results. The digital elevation model was generated from Pléiades stereo images and resampled from 8 to 30, 90, 250, 500, and 1,000 m. The results indicate that the model performs well from 8 to 250 m but the agreement with observations drops at 500 m. This is because significant features of the topography were too smoothed out to properly characterize the spatial variability of meteorological forcing, including solar radiation. We conclude that a resolution of 250 m might be sufficient in this area. This result is consistent with the shape of the semivariogram of the topographic slope, suggesting that this semivariogram analysis could be used to transpose our conclusion to other study regions.

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Regional flood frequency analysis in the High Atlas mountainous catchments of Morocco

Cited by 23 publications

References 31 publications

Impact of the dry-day definition on Mediterranean extreme dry-spell analysis

Impact of the dry-day definition on Mediterranean extreme dry-spell analysis

Variations of the Snow Water Equivalent in the Ourika Catchment (Morocco) over 2000–2018 Using Downscaled MERRA-2 Data

Effect of Digital Elevation Model Resolution on the Simulation of the Snow Cover Evolution in the High Atlas

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