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 LESSON 1 |
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LESSON 1 |
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Water is a vital nutrient for our survival. All living things need water to survive. Human beings can live for only a few days without water, but we can live for weeks without food. In fact, some bacteria can even live without oxygen, yet they cannot survive without water. Water is essential for every system in the human body. The body is 70% water, and water makes up 83% of our blood. Although water covers almost 80% of the Earth, 97% of that is salt water, which we cannot drink. In addition, glaciers hold about 2% of the Earth's water in glacial ice. Therefore, less than 1% of all water on Earth is fresh water that humans can use -- making it an invaluable resource. Knowing more about water is an important first step in keeping water sources in the Catskill region free from contamination.
The Water Molecule
Atoms are the smallest particles of elements such as hydrogen and oxygen, and when atoms join together, they form molecules. The water molecule is made up of two hydrogen (H) atoms, and one oxygen (O) atom: giving us H2O. Water is the most common solvent in nature. A solvent is a liquid with the ability to dissolve other substances. For example, water can dissolve the minerals found in our bodies. Pure water is colorless, tasteless, and odorless, and can occur in three states: solid, liquid, and gas.
Water as a solid - When water freezes, it turns to ice. The molecules move farther apart, so ice is less dense than water and it floats. Water freezes at 0C or 32F.
Water as a liquid - This is the state most familiar to us. We use water in many ways in its liquid form for washing, drinking, and as a solvent.
Water as a gas - After liquid water evaporates, it becomes an invisible vapor. Water becomes a gas when it reaches 100C or 212F. In the atmosphere, the vapor condenses onto dust particles, and depending on the air temperature, it falls as either rain or snow.
The Water Cycle
The amount of water on Earth is finite. The hydrologic cycle or water cycle is how water is recycled on Earth. The sun heats up liquid water found in streams, ponds, lakes, and oceans, which then evaporates into the sky. This evaporated water can form clouds in the atmosphere and then return to Earth as precipitation. In what form the water drops to the ground, what it does when it hits the ground, and how the water evaporates back into the sky vary. When water falls on land, it can either seep into the ground or stay on the surface to become "runoff", such as in streams and rivers. Surface water in smaller streams eventually collects into larger streams, and then into basins such as ponds, lakes, reservoirs, or rivers.
Groundwater
Water that goes into (infiltrates) the ground is called groundwater. Groundwater is the Earth's underground supply of water. It moves (percolates) through the pores or spaces between soil particles at different speeds, depending upon soil type. For example, sandy, porous soil would have a very fast rate of percolation, while thick, clay-like soil would slow the movement of the water. If a polluting substance such as oil were released into the ground, the percolation rate of the soil would determine how quickly the surrounding areas are contaminated. Additionally, in the Catskills, knowing the "perc" rate of soils is required for septic tank installation.
As water seeps into the ground, some of it clings to soil particles and plant roots near the surface. Plants draw in water from their roots to use when making food, a process called photosynthesis. Trees also use a tremendous amount of water -- they draw water in by their roots, transport it up their trunks, and then release water vapor from the underside of their leaves. This evaporation of water from the leaves is called transpiration. Forests in the Catskills are being studied right now to understand their effects on the quality and amount of water in the New York City Watershed.
Water percolating into the ground will eventually reach a zone of saturation called an aquifer. This level of water (commonly called the water table) rises or falls depending on precipitation and the amount withdrawn. The water table is what well drillers look for when drilling wells. Wells may be less than 100 feet or more than 700 feet deep, depending upon the level of the water table in a given area. If there were heavy precipitation for an extended period, the water table would be high. Similarly, a drought would lower the water table. The shape of the land surface (topography), soil porosity, depth to bedrock, and type of bedrock also influence the water table. In the Catskills, since glacial soils predominate, the depth of the water table varies significantly from one area to another. Springs form where groundwater comes to the surface.
Watersheds
A watershed divide marks the boundary between different basins of water collection. That invisible boundary is located at the tops of ridges and mountains and directs the flow of water into one basin or another. By studying these basins and the land use within them, one can make plans to keep the streams clean. Watersheds can be studied in different ways and on different scales. For example, using a cake pan and rocks covered with foil, students can make and study a miniature watershed. Or, on a much larger scale, students can study the Hudson River and all of its tributaries, including ponds, lakes, forests, farms, towns, and wetlands, as a collection of sub-basins or sub-watersheds.
To research a watershed, you must first determine the size of the basin to be studied and identify its boundaries. Then, gather information on the watershed, including all the physical, biological, geological, and social data that can be collected. By studying the current uses and the historyof a watershed, one can begin to understand it. Examining the effects that industry and agriculture have on the watershed will help us understand what steps need to be taken to insure good water quality. The final part of the "information gathering" step is to go out into the field and verify the material collected by personal observation. Then it's possible to formulate plans for the future of that watershed. Monitoring streams and establishing baseline data throughout the watershed supports discussion about different types of development.
Watersheds are studied for their geology, climate, erosion, slope, vegetation, and political boundaries. According to Karen Edelstein's Watershed Monitoring Handbook, there are approximately 70,000 miles of rivers and streams in New York State which drain 17 major watersheds. The Catskill region supplies water to the Delaware, Susquehanna, Mohawk, and Hudson Rivers.
Several watersheds in the Catskills supply water to New York City's six reservoirs in the region. This major water use has had dramatic effects on Catskills communities, from the loss of towns to make way for the reservoirs, to the ongoing regulations needed to maintain water quality. Water has influenced the Catskills in many other ways as well -- not just as a water supply for New York City. The Catskill Mountains are actually famous for their streams. For example, the Hudson River School of landscape painting made the creeks and valleys of the Catskills famous throughout the world for their scenic beauty. American fly-fishing also began in the Catskills, and our streams are considered among the best in the world for that sport. Yet the streams are only as healthy as their surrounding watersheds. The study of water pertains not only to the streams themselves, but also to the surrounding land and the people living on that land.
Note: Portions adapted from Bock, Rosalie, The Story of Drinking Water, American Water Works Association, 1990.