The Sudans Nile within the Sudans has no significant tributaries. The amount of rainfall increases towards the south. In the north there is the very dry Nubian Desert; in the south there are swamps and rainforest. The Sudans’s rainy season lasts for about three months (July to September) in the north, and up to six months (June to November) in the south. The dry regions are plagued by sandstorms, known as haboob, which can completely block out the sun. In the northern and western semi-desert areas, people rely on the scant rainfall for basic agriculture and many are nomadic, travelling with their
Colorado Desert rare ecological communities found only in the Colorado Desert. They occur only where permanent water sources are available, such as at springs or along fault lines, where groundwater is forced to the surface by the movement of hard impermeable rock, and can be found in the San Jacinto, Santa Rosa, and Little San Bernardino mountains, in the canyons of Anza-Borrego Desert State Park, and along the San Andreas Fault in the Coachella Valley. The only palm native to California, "Washingtonia filifera" (desert fan palm), grows at the oases. Some sub-regions of the Colorado Desert contain endemic flora. Along the Lower