The Arid Zones

Africa agriculture Alice Springs alluvial fans amount animals annual aquifers arid areas arid lands arid zone artesian basins Australia Barrage basins camel cattle cent Central Asia chemical weathering chernozems climate crops cultivation Cyrenaica dams deposits desert locust drainage drought dry lands dunes East economic environment erosion evaporation extend extremely arid floods grazing ground ground-water higher hot deserts increase inselbergs irrigation isohyet Lake latitudes layer less locust loess lower major margins Mediterranean miles mineral Nile nomadic North America numbers oases oasis occur Old World pastoralism pedocals perennial irrigation period plains plants Pleistocene pluvials precipitation problems rain rainfall relative humidity reservoirs river rock run-off Sahara saline salt sand savanna seasonal sediments semi-arid semi-arid lands sheep showers slopes solonchaks south-west southern steppe steppe lands summer supply surface temperate deserts temperature tion transhumance Tunisia utilisation valley vegetation wind winter xerophytes