HDY443 Lecture 11.1 Chapter 7 Groundwater Hydraulics ZZZZ (1).pptx

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HDY443 Hydraulics and Hydrological Engineering. LAWRENCE MALESU PHD, P.ENG
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Lecture 12 and 13 Groundwater Hydraulics
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Introduction Types of Aquifers Movement of Groundwater. Dacy velocity and seepage velocity Steady Radial flow to a well ( in Confined and unconfined aquifers. Determining aquifer characteristics (K, T and S values) for steady radial flow confined aquifers. Aquifer boundaries Surface investigation of groundwater. Seepage through dam formations 3 Content
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Introduction Groundwater is defined as all the water in the ground occupying the pore spaces within bedrock and regolith ( the layer of loose material covering the bedrock of the earth) . Generally the volume of groundwater is larger than the volume of all water in fresh-water lakes or flowing in streams ( Ram S Gupta ). Most ground water originates as rainfall. Water is present everywhere beneath the land surface, but more than half of all groundwater, including most of what is usable, occurs above a depth of 8 km
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Water Bearing formations Formations that can yield/hold significant amount of water are called aquifers. An aquifer is a body of highly permeable rock or regolith that can store water and yield sufficient quantities to supply wells Most aquifers are in the form of alluvial deposits, which are considered as best aquifers since they have advantages of direct replenishment by seepage from streams and land. Rock formations of volcanic nature ie limestone and sandstones possess cracks, cavities, faults and joints through which they yield water, quality of such aquifers depends of such openings – sometimes form high permeable aquifers.
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Types of Aquifers Aquifers are of two types: Confined aquifers is a relatively high permeability, water bearing formation (ie Sand or gravels) confined below a layer of very low permeability e.g clay (bounded by an impermeable body of rock or stratum of sediment that acts as a barrier to the flow of water - aquicludes). Unconfined is a relatively high permeability, water bearing formation with a defined Water Table, a free surface subjected to atmospheric pressure from above and below which the soil is completely saturated (an aquifer that is not overlain).
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Water Table The zone of aeration (also called the unsaturated zone ) is a layer of moist soil followed by a zone in which open spaces in regolith or bedrock are filled mainly with air. Beneath the unsaturated zone is the saturated zone , a zone in which all openings are filled with water. The upper surface of the saturated zone is the water table. Fig 7.1 text book, Shows several examples of groundwater formations.
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Groundwater moves due to gravitational slope or hydraulic gradient.
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