Humans affect the water cycle in numerous ways. Some of our actions purposefully affect the water cycle and other human activities have unintentional consequences on the water cycle.We pull water out of the ground in order to use it. We change the flow of water using irrigation. We dam lakes and rivers for electricity and to create manmade lakes and ponds. The Colorado River in the US no longer reaches the ocean at times because humans have altered it so much.Climate change is causing numerous changes to the water cycle. Sea levels are rising in some areas and dropping in others, glaciers are retreating and disappearing affecting rivers, droughts are happening more frequently in some regions and floods in other areas, coastlines are changing and some islands are disappearing, the polar ice cap is melting, and so forth.
The use of pesticides, herbicides, and excess nitrogen for farming runs off into rivers and streams and pollutes groundwater. Deforestation, whether for timber or to clear land for agriculture or development, increases runoff. Certain emissions from industry cause acid rain .
