Why do we have a limited supply of water? We have a limited supply of water because 97% of the water is salt water and about 75% of the fresh water is ice. Fresh water is renewed through the water cycle. Images Showing: All colors ▼ All colors ▼ Results of about 30,400,000 (0.04 seconds)

What causes water shortages? Water shortages happen when people use water faster than it is replaced. This is most likely to happen during a drought, which is a period where less rain than normal comes.

Water Pollution Water pollution is any change to water that can harm living things. Some pollutants just make water unpleasant, some can cause sickness or death. Most pollution is caused by human activities like sewage, agricultural wastes, industry and mining, sediments, oil and gasoline, and heat.

Sewage and Agricultural wastes Sewage is human wastes. When untreated sewage mixes with water, it can make organisms very ill. If treated sewage mixes with water, the bacteria in the water will feed on it and multiply, which takes oxygen out of the water. Animal waste, pesticides, and fertilizers can cause pollution because the rain can wash them into the water.

Industry and Mining Factories and mining sites can release chemicals and metal into the water and make organisms sick.

Sediments Sediments are particles of rock, silt, and sand. Sediments cover up food sources, nesting sites, and eggs of organisms. They also block the sun, which makes underwater plants not able to grow.

Oil and Gasoline Oil spills are one of the most dramatic forms of water pollution. It can cause organisms to die from swallowing it. Birds can get it in their feathers and not be able to fly. Gasoline can leak out of storage tanks underground and pollute the groundwater.

Heat Some factories release water that was used to cool hot machinery. This heated water can cause the temperature of the water to change, which kills the organisms.