The soil of the Thar Desert remains dry for much of the year and is prone to wind erosion. High velocity winds blow soil from the desert, depositing some on neighboring fertile lands, and causing shifting sand dunes within the desert. Sand dunes are stabilised by erecting micro-windbreak barriers with scrub material and subsequent afforestation of the treated dunes with seedlings of shrubs such as phog, senna, castor oil plant and trees such as gum acacia, Prosopis juliflora and lebbek tree. The 649 km (403 mi) long Indira Gandhi Canal brings fresh water to the Thar Desert. It was conceived to halt spreading of the desert to fertile areas.