Water Underground: *Where We Get Most of Our Freshwater *
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Water Underground: *Where we get most of our freshwater!!!*
How Water Moves Underground Water underground trickles down between spaces in soil and through cracks and spaces in layers of rock.
Effects of Different Materials Different types of rock and soil have different-sized spaces between their particles. The size of the spaces determines how easily water moves through rock and soil. If the spaces are connected, this too affects water movement. Because they have large and connected spaces, materials such as sand and gravel allow water to pass through, or permeate. They are thus known as permeable materials. As water soaks down through permeable rock and soil, it eventually reaches layers of material that it cannot pass through. These materials have few or no spaces or cracks. Clay and granite are impermeable, meaning that water cannot pass through. When water reaches the impermeable materials it is trapped and forms the water table – where we get our water.
Water Zones Once water reaches an impermeable layer, it is trapped. It can’t soak any deeper. Instead, the water begins to fill up the spaces above the impermeable material. The area of permeable rock or soil that is totally filled, or saturated, with water is called the saturated zone. The top of the saturated zone is the water table. Soil and rock layers above the water table contain some moisture, too. Here the pores contain air as well as water and are not saturated. Therefore, the layer of rocks and soil above the water table is called the unsaturated zone. Bringing up Groundwater Any underground layer of rock or sediment that holds water is called an aquifer. Aquifers can range in size from a small underground patch of permeable material to an area the size of several states The water is moving, seeping through layers of rock. The depth of a water table can vary greatly over a small area. People can obtain water from an aquifer by drilling a well below the water table. In an artesian well, water rises because of pressure within an aquifer (natural well). Uses of Water (1) How many categories of water use are shown on the graph? 4 (2) What are the two largest categories of water use combine to make up about what percentage of the total water used in the United States? Agriculture and Power Plants combined make up 80.5% of total water used in the U.S.
(3) Which of the categories of water use shown in the graph represents the largest use of water in the United States? Which represents the smallest? Agriculture = largest, industries and mining = smallest (4) How would an increase in the number of farms affect this graph? The percentage for agriculture would increase, and the percentage available for all of the other uses would have to decrease. Water Underground Questions: 1. What happens to water in the ground when it reaches the impermeable materials? - It is trapped and forms the water table. 2. What two factors determine how easily water can move through underground materials? - The size of the spaces of the underground materials and whether the spaces are connected. 3. Would an impermeable material have large or small spaces? Would the spaces be connected or unconnected? - Impermeable material would have small spaces or none and they would be unconnected. 4. How could people obtain water from an aquifer? - They could drill a well down below the water table.