122x Filetype PPTX File size 0.06 MB Source: www.johnston.k12.nc.us
Freshwater • Since 70% of Earth’s freshwater is frozen in ice, we split the remaining usable freshwater into two categories: groundwater and surface water. • Surface water is found in lakes, streams, and rivers, while groundwater is found underground in aquifers. • Both forms are replenished by the water cycle through precipitation, however, runof water will feed lakes, rivers, and their tributaries (streams that flow into rivers) while water that infiltrates and drips through the ground will feed the aquifers there. Freshwater continued….. • As the runoff flows over land it can pick up pollutants and other materials that negatively affect its quality. • Groundwater on the other hand, is filtered as it drips through the many layers of rock that lead to the aquifer. Water Quality • Because both freshwater and saltwater resources are so vital to living things on Earth, it is important that we maintain their quality by keeping them clean. • In general, water quality refers to the cleanliness of water and is determine by looking at a variety of physical and chemical factors. • For example, the health of a river system is best judged by nitrate levels and turbidity while a lake used for freshwater, is assessed by temperature and pH. Water Quality continued….. • In the United States, the Environmental Protection Agency (EPA) is responsible for regulating the quality of natural resources such as air and water by setting limits on the 90 most common pollutants and contaminants since excessive amounts of tem are considered dangerous to our health. • Physical aspects of water quality include its temperature, turbidity (how cloudy the water is), and rate of water movement. • Even though living things can survive in a range of temperatures, aquatic animals generally need to be in cooler water because at warmer temperatures, the water contains less dissolved oxygen and other nutrients which are needed to support them. Water Quality continued…… • Because the increased temperature can kill off or force the migration of a species away from the area, the entire ecosystem can easily become unstable or collapse. • Water with higher turbidity is cloudier because there are more solids and sediments suspended in it. • Since many of these solids come from pollutants, lower turbidity is better for most living things. • This cloudiness can also prevent sunlight from getting into the water reducing the amount of photosynthesis present.
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