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Groundwater. Where’s the Water?. Water can be reached from anywhere on Earth if a deep enough well is drilled All water on and in Earth’s crust makes up the hydrosphere 97% of all Earth’s water is in the oceans 3% of all Earth’s water is considered freshwater
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Where’s the Water? • Water can be reached from anywhere on Earth if a deep enough well is drilled • All water on and in Earth’s crust makes up the hydrosphere • 97% of all Earth’s water is in the oceans • 3% of all Earth’s water is considered freshwater • 90% of all freshwater is in polar ice caps and glaciers • 10% that remains is groundwater • <0.5% is easily accessible (lakes, streams, etc)
Zone of Saturation • Depth at which groundwater completely fills all the pores of a material • Gravitational – trickles downward due to the force of gravity • Capillary – drawn upward from the water table and held in pore spaces due to surface tension • The upper boundary of this zone is the water table
Location Matters • Water table follows the topography of the land above it • Water table depth depends upon local conditions • Stream valleys • Few meters deep • Swampy areas • At Earth’s surface • Hilltops, arid regions • Tens to hundreds of meters deep
Groundwater Movement • Rate of movement depends on two factors • Permeability of material (most important) • Slope of the water table • Most groundwater flows through permeable layers called aquifers • Aquicludes are impermeable layers • Clay (most impermeable), silt, shale