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Chapter 10 Groundwater. Learning Targets. 10.1 - Movement and Storage of Groundwater I can explain how ground water infiltration, storage and movement results in such a high quality source of water for Dubuque. 10.2 – Groundwater Weathering and Deposition
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Learning Targets 10.1 - Movement and Storage of Groundwater I can explain how ground water infiltration, storage and movement results in such a high quality source of water for Dubuque. 10.2 – Groundwater Weathering and Deposition I can apply my knowledge of water as a universal solvent to features of karst topography and the chemical content of water.
Targets continued 10.3 – Ground Supply I can describe the major problems that threaten groundwater supplies. I can explain how water in Dubuque is prepared for consumption and treated after use.
Hydrosphere • Oceans _____ % of all water • Freshwater _____ % of all water • Groundwater ___ % of all freshwater • Ice/Glaciers ____% of all freshwater • Lakes/Rivers/Streams ____% of all freshwater 97 3 23 76 1
precipitation Infiltration permeable saturation impermeable aquifer aquiclude
Factors that influence infiltration • Slope • Particle size • Porosity • Moisture content of soil • Ground cover • Permeability
What determines the flow velocity of groundwater? • Slope of the water table • Permeability of material
Dubuque’s Water Supply The Eagle Point Water Plant is supplied by five shallow and four deep wells. It serves an average water demand of eight million gallons daily.
Water Sources • The Dubuque Water Department obtains water from the Alluvial aquifer and the Cambrian-Ordovician aquifer. • Every aquifer has a degree of susceptibility to contamination because of the characteristics of the aquifer, overlying materials, and human activity. Susceptibility to contamination generally increases with shallower aquifers, increasing permeability of the aquifer and overlying material, nearby development or agricultural activity, and abandoned or poorly maintained wells. • The Alluvial aquifer is considered to be highly susceptible to • contamination, while the Cambrian-Ordovician aquifer has a low degree of susceptibility to contamination.
10.2 – Groundwater Weathering and Deposition I can apply my knowledge of water as a universal solvent to features of karst topography and the chemical content of water.
Sinkhole Cave Cavern Stalactite Stalagmite
Irrigated Cropland 2002 56.6 million acres Highlighted In Red
Water Treatment • Eagle Point Treatment PlantThe Eagle Point Treatment Plant is a groundwater, lime softening, water treatment plant. Starting with source water that is virtually free of sediment, the lime softening process reduces the total hardness from about 280 mg/L to 120 mg/L. The process also removes organic matter that harbor taste, odor, and color.Treatment Process Overview • Aeration - Raw or untreated water is drawn from wells into the City’s treatment plant and is cascaded down through a series of trays, increasing the surface area of the water and promoting the exchange of gases. Aeration also removes undesirable gases such as radon. Aeration is similar to the natural process that occurs when a stream flows through rapids or over falls.
Flocculant Aid Addition - An anionic flocculant aid is added just after aeration. The flocculant helps to improve the clarity of the water by allowing fine particles to clump together and settle out. • Softening - Calcium oxide (lime) is mixed with water to form slaked lime. This slaked lime is then added to the water to soften or reduce the minerals that typically make water hard. Excessive hardness increases soap use, deposits scale in water heaters and boilers, interferes with some industrial processes, and sometimes gives water an unappealing taste and odor. The byproducts from the softening process are applied to farmland as a soil conditioner.
Recarbonation - The addition of slaked lime increases the pH of the water to about 10. In order to stabilize the softened water, the pH must be lowered. This pH reduction is accomplished by adding carbon dioxide until the pH is approximately 9.3. • Chlorination - Chlorine is added to disinfect the water. The chlorine helps ensure our water’s microbiological safety by destroying disease-causing organisms. • Filtration - Water is then passed through a sand and gravel filter bed, removing any remaining suspended matter.
Fluoridation - Fluoride is added to help prevent tooth decay. • Phosphate Addition - Phosphate is added to chemically stabilize the water and lessen the possibility that lead will leach out of pipes and into tap water. • Reserves - Water not immediately consumed flows into storage tanks for use when demand exceeds plant pumpage. Water stored in elevated tanks helps stabilize pressure in the distribution system and serves as an emergency reserve for fire protection. • Distribution - Finished water is pumped directly into the water distribution systems that serve homes and businesses throughout the city of Dubuque.
