AP BIOLOGY

Detailed explanation-1: -Deforestation and agriculture reduce the amount of water vapor released by trees and vegetation into the atmosphere thus resulting in low amounts of rain (Nelson, 2003). In addition, loss of ground cover makes land drier and causes increased run-off and leaching.

Detailed explanation-2: -Heavy use of agricultural machinery can compact the soil and reduce its infiltration capacity, making runoff more likely. Changing greenfield surfaces to impermeable concrete and tarmac as construction takes place can increase the level of runoff in an area.

Detailed explanation-3: -Runoff from nonpoint sources includes lawn fertilizer, car exhaust, and even spilled gasoline from a car. Farms are a huge nonpoint source of runoff, as rainwater and irrigation drain fertilizers and pesticides into bodies of water. Impervious surfaces, or surfaces that can’t absorb water, increase runoff.

Detailed explanation-4: -Humans directly change the dynamics of the water cycle through dams constructed for water storage, and through water withdrawals for industrial, agricultural, or domestic purposes. Climate change is expected to additionally affect water supply and demand.

Detailed explanation-5: -Tillage of land changes the infiltration and runoff characteristics of the land surface, which affects recharge to ground water, delivery of water and sediment to surface-water bodies, and evapotranspiration. All of these processes either directly or indirectly affect the interaction of ground water and surface water.