Introduction to Groundwater

Transcription

1 Introduction to Groundwater Unit Essential Questions: How does the Earth cycle its water through its major reservoirs? How does society s use of resources affect water quality? Presentation Objectives: Define groundwater and the groundwater profile. Identify and describe factors that influence the amount of groundwater. Identify and describe factors that influence the speed of groundwater flow. Define permeability, aquifer, aquiclude, and confined aquifer. Explain how a water budget works. How Much Is There? The hydrosphere includes all of the water both on and in the Earth. 71% of the Earth is water! - Saltwater - Freshwater - Water Vapor 2.6% of Earth s Water Distribution of Freshwater More than 90% is in the icecaps and glaciers. 0.31% is in groundwater 0.009% is in lakes % is in rivers and streams. Q1 Most useable water! What is Groundwater? Groundwater is water that is stored in the pore spaces of ground material. Groundwater is the result of infiltration. Process by which precipitation or snow melt seeps into the ground and becomes groundwater. It s all part of the cycle! Groundwater flows. Returns to the surface. Enters lakes, rivers, or the ocean. Q2 Ready, Set, Infiltrate! Which will allow water to infiltrate more? Soil A Soil B Soil C Porosity - is the amount of pore space in a material. Well-sorted soil has a higher porosity than unsorted soil. Cements of sedimentary rocks reduce porosity. The higher the porosity, the greater the infiltration! Q3

2 The Groundwater Profile Q4 The Groundwater Profile Q4 Zone of Aeration Pore spaces are filled with air. Capillary fringe Small amount of water present in the zone of aeration. Pulled into small spaces by capillary action. Water Table The upper boundary of the zone of saturation. Zone of Saturation Pore spaces are filled with water. Groundwater is found in the zone of saturation! Q5 The Water Table The location of the water table depends on local conditions. Topography Water table typically follows the slope of the land. By Gosh it Moves! Groundwater flows downhill through the soil! Q6 Climate and Weather Higher when it is rainy. Lower when it is dry. The speed of groundwater flow depends on the slope of the water table. The steeper the water table, the faster its flows! The pull of gravity is stronger!

3 A Place To Flow The speed of groundwater flow also depends on the soil s permeability. Permeability is the ability of a material to let water pass through. A soil with a high permeability has large, connected pores. Sand, gravel, limestone, fractured bedrock. A soil with a low permeability has tiny, unconnected pores. Fine-grained silt, clay, and shale. The higher the permeability, the faster the groundwater flows! Q7 Real World Application Landfills are lined with clay at the bottom. Doesn t allow toxic chemicals to leak out because its impermeable. Q8 Where s the Water? Groundwater flows in an aquifer. Permeable layers where groundwater flows. Top boundary is the water table. Water can be extracted using a well.! Aquiclude - a layer of impermeable rock that groundwater CANNOT flow through. Q9 Recharge Zone A confined aquifer has to have an opening to the Q10 surface where water can enter into the permeable layer. Known as recharge zone. Confined Aquifer An aquifer sandwiched between two aquicludes. Impermeable Permeable Impermeable

4 Would You Like A Drink? Most groundwater is retrieved using a well, which is a hole dug into the ground to reach an aquifer. Q11&12 Under Pressure Q13 The water level in a well is determined by pressure. Types of wells Ordinary well Taps into a water table/ unconfined aquifer. Artesian well Taps into a confined aquifer. To access a well s water we use a pump to draw the water upward rather than let it travel on its normal course. The pressure surface is known as the potentiometric surface. The water level in a well is where the pressure line intersects the well. Under Pressure Confined aquifers have higher pressure, so the water level is higher than a normal aquifer. Sometimes the potentiometric surface is above the Earth s surface. - Known as a flowing artesian well. - Water flows out all by itself! Q14 Groundwater Discharge Q15 Groundwater flows until it becomes surface water. Often enters into streams, lakes, ponds, swamps or the ocean. Sometimes, the water table will intersect the land surface and groundwater will naturally flow onto the Earth s surface. Groundwater Spring!

5 Nice and Hot! Q16 Spring water is usually the average annual temperature for a given location. New England springs are about 10 C. Hot springs Temperatures are higher than the human body. East - aquifers that go deep into the Earth s crust. After the first 20 meters, the temperature increase about 1 C every 40 meters. West - linked to volcanic activity in the area. Special Hot Springs Mud pots are hot springs Geysers are hot springs that where the groundwater has erupt water to the surface. dissolved rocks into clay. Yellowstone National Park