Water for Life
Life on Earth is dependent on clean water. Water quality is defined as the stability of water for a particular use. A definition of good water is different for drinking water than for a lake. Because water is so important for life, we monitor different chemicals and physical and biological characteristics and work to ensure good water quality.
Water, Water Everywhere
Water in the ground, called groundwater, is an important source of water on Earth. The ground is different in different places, and some ground materials hold water better than others. An aquifer is an area of ground that holds water well/. Water moves into the ground from rain, snow melt, or other sources. Then it sins until it gets to a layer it can’t move through. This layer might be clay or certain kinds of rock.
Water can fill aquifers, where deep water might remain for hundreds of years, and shallow water can flow to places where it reaches the surface, like ponds, lakes, and springs.
There is much more freshwater in the ground than on Earth’s surface, and groundwater is drawn out using wells.
Water Quality=Quality of Life
To evaluate a pond’s ability to support life, we might measure characteristics like the following: dissolved oxygen(DO)-because fish and most other aquatic animals breathe DO: PH-if pHis too far from neutral, either acidic or basic, organisms may be unable to survive; water temperature-warmer water holds less oxygen, so animals might avoid areas of high temperature. In this pond, at certain times, we might also check salinity (the salt concentration).
Freshwater has a salinity of 0 ppt (parts salt per thousand parts water). When Dauphin Island is hit by a hurricane, saltwater may wash over parts of the island and enter the pond or the groundwater. This can affect the island’s human population, who use groundwater in their homes, and also the animals that live in the pond.
These are just a few examples of water qualities that might affect those using the water.
At Gaillard Lake, you can see where the water table becomes a like surface. When you look at the lake, can you tell oxygen, pH, temperature, or salinity levels? Does the water look dirty?
You may not be able to determine levels by looking, but if you pay attention, you might notice hints bout a lake's water quality. Can you find a diversity of fish, turtles, alligators, frogs, or insects in the water? Are birds feeding from the lake? These signs suggest good water quality, but they are not definitive-sometimes animals are forced to use poor-quality lakes. Water cooler is not a definite marker either - this lake is often a brown color, like tea. This is natural. It is from tannins that leach out of soaking leaves or pine needles.
Aquatic invertebrates are used to assess water quality. Some, like those seen above (larvae of left to right: caddisfly, stonefly, and mayfly), have a low tolerance for pollution. If they are found in a sample, the water quality is likely good. Others, like the pouch snail and mosquito larva at left, have a high tolerance for pollution. If a sample has mostly animals like these and very few of those from the first group, water quality is likely poor.
In the U. S., for water intended for human use, there are established standards for acceptable levels of dissolved or suspended matter, like bacteria, heavy metals, and others that are potentially harmful. Our municipal water usually follows a path such as this one: water is withdrawn from a natural source, filtered and sterilized, piped into our homes; flushed down our drains; filtered, treated, and the solid waster is taken to one disposal site, while the water is released back to a natural location. Water used in homes on Dauphin Island is groundwater from the island (it is not piped in). Processed water is stored in the water tower seen at right.
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