The Water Cycle

Water is almost constantly on the move. The path it travels from the clouds to your yard into the river or lake and back into the clouds is called the water cycle.

In areas without a lot of roads and houses the natural water cycle works to filter pollutants from water as well as to recharge groundwater. The urban water cycle is different because impermeable surfaces, such as roads, parking lots, rooftops, or even compacted soil, stop water from soaking into the soil. Instead, most of the water flows quickly over these surfaces, picks up oil, salt, animal waste, pesticides and a host of other pollutants and slips into the storm sewer. The storm sewer quickly dumps this polluted water into nearby streams, rivers and lakes. When rain or snow melt is heavy, a surge of water can lead to flooding and massive erosion.

Understanding the path of water within the water cycle and how it changes in the urban environment is a key step to solving the problem of river pollution. The next step is understanding the pattern of water drainage across the landscape.

More information: Natural Water Cycle , Urban Water Cycle

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