Urbanization can put water-quality pressures on rivers.

To some degree, "urbanization" (people living together in groups), has been taking place since ancient times. As populations rose and people mastered techniques to grow food in fixed locations, groups of people became settlements and then towns and cities. In the United States, the speed of this urbanization picked up after World War II, and now many urban areas are growing at a record pace. What are the effects on the local hydrologic system when a rural area is turned into an area full of housing developments, shopping centers, industrial buildings, and roads?

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