7.9c

A student sets up the investigation shown below. The movement of colored water through the gravel best models —

• condensation of water vapor

• pollution of groundwater

• surface runoff of precipitation

• conservation of water

A student’s model of an area near a city depicts many activities that affect the quality of the water in the area. How does the agricultural activity most likely affect the surface water of the area?

• Excess crop fertilizer is carried by runoff into the river, causing excess growth of water plants.

• Excess crop material accumulates on the riverbanks, slowing the movement of the river water

• Crops reduce erosion, increasing the amount of soil entering the river.

• Crops absorb pure water from soil, causing the remaining water to contain more salt.

A student drew the model below to represent a part of a watershed and some human activities that affect the watershed. How do the industrial, agricultural, and residential activities of humans most likely affect the groundwater in the area?

• The activities prevent most of the water from evaporating into the atmosphere.

• The activities replace the groundwater used.

• Pollutants from the activities percolate through the soil and enter the water table.

• All of the above

When runoff crosses the land, it picks up fertilizers that have been used on crops and lawns. These contaminants will eventually enter a lake, river or stream, which may lead to -

• the Earth's surface to sink

• the water in the aquifer to drop

• harmful rapid growth of algae

• cleaner water for drinking and bathing

An area experiences a long period of drought forcing towns to pump out almost all of the water held in aquifers. What is the most likely result of this over pumping?

• stability of underground rock layers will be weakened

• excessive growth of plants will occur in local lakes

• rainfall levels will increase and fill the aquifer

• a dead zone will be created in the watershed

Which of the following human activities would most likely lead to subsidence, the sinking of the surface of the earth?

• excess removal of water from underground reservoir

• using toxic materials in the manufacturing of goods f

• filtering out pollutants in a water treatment plant

• storing drinking water in small above-ground basins

Which of the following is the most reasonable explanation of why a well drilled into an aquifer would fail to produce water?

• pollutants have seeped into the groundwater

• excessive growth of algae has killed local pond life

• over pumping has exceeded rain water replenishment

• runoff contains chemicals has caused a dead zone

When the student sprays water onto the model, red color appears in the cloth and in the water in the layer of marbles. Which part of the model represents pollutants introduced by humans?

• the marble

• the thick cloth

• red powdered paint

• layer of sand