Preprints
https://doi.org/10.5194/hess-2020-622
https://doi.org/10.5194/hess-2020-622

  18 Dec 2020

18 Dec 2020

Review status: a revised version of this preprint is currently under review for the journal HESS.

Future projections of High Atlas snowpack and runoff under climate change

Alexandre Tuel1,a, Nabil El Moçayd2, Moulay Driss Hasnaoui3, and Elfatih A. B. Eltahir1 Alexandre Tuel et al.
  • 1Ralph M. Parsons Laboratory, Massachusetts Institute of Technology, 15 Vassar St., Cambridge 02139 USA
  • 2International Water Research Institute, University Mohammed VI Polytechnique, Lot 660 Hay Moulay Rachid Benguérir 43150, Morocco
  • 3Ministry of Equipement, Transport, Logistics and Water, Department of Water, Morocco
  • acurrent affiliation: Institute of Geography, Oeschger Centre for Climate Change Research, University of Bern, Bern

Abstract. The High Atlas, culminating at more than 4000 m, is the water tower of Morocco. While plains receive less than 400 mm of precipitation in an average year, the mountains can get twice as much, often in the form of snow between November and March. Snowmelt thus accounts for a large fraction of the river discharge in the region, and is particularly critical during spring, as the wet season ends but the need for irrigation increases. In the same region, future climate change projections point towards a significant decline in precipitation and enhanced warming of temperature. Understanding how the High Atlas snowpack will evolve under such trends is therefore of paramount importance to make informed projections of future water availability in Morocco. Here, we build on previous research results on snow and climate modeling in the High Atlas to make detailed projections of snowpack and river flow response to climate change in this region. Using a distributed energy balance snow model based on SNOW-17, high-resolution climate simulations over Morocco, and a panel regression framework to relate runoff ratios to regional meteorological conditions, we quantify the severe declines in snowpack and river discharge that are to be expected, even under a scenario of substantial mitigation of emissions. Our results have important implications for water resources planning and sustainability of agriculture in this already water-stressed region.

Alexandre Tuel et al.

 
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Alexandre Tuel et al.

Alexandre Tuel et al.

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Short summary
Snowmelt in the High Atlas is critical for irrigation in Morocco, but is threatened by climate change. We assess future trends in High Atlas snowpack by modeling it under historical and future climate scenarios, and estimate their impact on runoff. We find that the combined warming and drying will result in a roughly 80 % decline in snowpack, a 5–30 % decrease in runoff efficiency and 50–60 % decline in runoff under a business-as-usual scenario.