The Water Cycle

Figure 1. Schematic diagram of the water cycle in a river basin. Water flowing out the lower right-hand corner is either used downstream or returned to the ocean, where it evaporates, eventually to form precipitation. Sources of water for the basin are rain- and snow-fall, and, possibly, water imported from other basins by societal diversion projects. Blue arrows represent “pure” water; red arrows represent losses due to evapo-transpiration. Dark arrows represent water contaminated by mine tailings, agricultural by-products, or municipal/industrial use. At present, most acquifers are being pumped faster than they are being recharged.

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