6 Underground Layers Where does underground water come from? Answer: Precipitation that soaks in the ground and trickles downward.Water underground trickles down between particles of sol and through cracks and spaces in layers of rock.
7 Pores - different types of rock and soil have different-sized spaces. Permeable - materials that allow water to easily pass through or permeate.Examples of permeable materials are sand and gravel.
8 Impermeable - materials that water cannot pass through easily. Examples of impermeable materials are clay and granite.Saturated zone - the area of permeable rock or soil tat is totally filled or saturated with water.
9 Water table - the top of the saturated zone. Unsaturated zone - the layer of rocks and soil above the water table.
10 Layers UndergroundWhat is different about the pores in the two pictures?Which picture represents a permeable rock layer?In this picture how do the pores differ above and below the water table?
11 AquifersAquifer - any underground layer of rock or sediment that holds water.Size - small underground patch of to an area the size of several states.
12 AquifersThe huge Ogallala aquifer lies beneath the plains of the west, from S. Dakota to Texas. It provides drinking water and water for crops and livestock.
13 AquifersThe water in aquifer moves only a few centimeters a day which equals out to be about 10 meters a year. The movement depends largely on how steeply the aquifer slopes and how permeable the rocks are.
14 WellsPeople can obtain groundwater from an aquifer by drilling a well below the water table.Fig Compare the well and dry well.
15 Wells History of wells Dug by hand Lined with brick or stone to keep the walls from collapsing.Lowered and raised a bucket to brink up water.Today, most are dug with well-drilling equipment.
16 WellsPumping water out of an aquifer lowers the water level near the well. If too much water is pumped out too fast, the well may run dry.Then it may be necessary to dig deeper to reach the lowered water table or to wait for rainfall to refill the aquifer.
17 Wells Recharge - New water that enters the aquifer from the surface. Artesian well - a well in which water rises because of pressure within the aquifer.
18 Bringing Groundwater to the Surface Springs - where the water table meets the ground surface, groundwater bubbles or flows out of cracks in the rock in places.