A snow volume-reducing and fluidisation device comprising: - a first fixed reservoir equipped with means to fluidise and reduce the volume of snow; - at least one second reservoir forming a storage basin of larger volume than the first reservoir, the volume of said storage basin being at least 20 times preferably at least 100 times the volume of the first reservoir, and said storage basin being at least partly filled with water at ambient temperature, preferably at least 30 % of its volume being filled with water; - at least one first fluid transfer conduit between an evacuation orifice at the lower end of said first reservoir and said storage basin; and - at least one second transfer conduit between said storage basin and said first reservoir; - said fluidisation means comprising: - snow compacting means comprising mobile dynamic compacting means; and - mechanical break-up means via chopping and/or mixing arranged below said compacting means and capable of forcing the snow moving downwards; and - water injection means, preferably comprising water spray nozzles (3a, 3b) inside and/or above the first reservoir and supplied with water from the storage basin via said second conduit, said water injection means being positioned at least above said chopping and/or mixing means, preferably also underneath said chopping and/or mixing means; and - ultrasound generating means comprising ultrasound-emitting devices supported by a rigid structure inside the first reservoir, arranged below said chopping and/or mixing means and below said water injection nozzles. - a first fixed reservoir equipped with means to fluidise and reduce the volume of snow; - at least one second reservoir forming a storage basin of larger volume than the first reservoir, the volume of said storage basin being at least 20 times preferably at least 100 times the volume of the first reservoir, and said storage basin being at least partly filled with water at ambient temperature, preferably at least 30 % of its volume being filled with water; - at least one first fluid transfer conduit between an evacuation orifice at the lower end of said first reservoir and said storage basin; and - at least one second transfer conduit between said storage basin and said first reservoir; - said fluidisation means comprising: - snow compacting means comprising mobile dynamic compacting means; and - mechanical break-up means via chopping and/or mixing arranged below said compacting means and capable of forcing the snow moving downwards; and - water injection means, preferably comprising water spray nozzles (3a, 3b) inside and/or above the first reservoir and supplied with water from the storage basin via said second conduit, said water injection means being positioned at least above said chopping and/or mixing means, preferably also underneath said chopping and/or mixing means; and - snow compacting means comprising mobile dynamic compacting means; and - mechanical break-up means via chopping and/or mixing arranged below said compacting means and capable of forcing the snow moving downwards; and - water injection means, preferably comprising water spray nozzles (3a, 3b) inside and/or above the first reservoir and supplied with water from the storage basin via said second conduit, said water injection means being positioned at least above said chopping and/or mixing means, preferably also underneath said chopping and/or mixing means; and - ultrasound generating means comprising ultrasound-emitting devices supported by a rigid structure inside the first reservoir, arranged below said chopping and/or mixing means and below said water injection nozzles.