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Flow in Aquifers Groundwater Hydraulics Daene C. McKinney

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Summary Confined Aquifer Flow – Continuity Equation – Steady Horizontal Flow – Transmissivity Unconfined Aquifer Flow – Continuity Equation – Steady Horizontal Flow – Steady Horizontal Flow with Infiltration – Drains

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Unconfined Aquifer Flow

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Flow in an Unconfined Aquifer Dupuit approximations – Slope of the water table is small – Velocities are horizontal Ground surface Bedrock Unconfined aquifer Water table xx QxQx K h x y z

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Steady Flow in an Unconfined Aquifer 1-D flow Steady State K = constant h Flow hAhA hBhB Water Table Ground Surface Bedrock L x

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Steady Flow in an Unconfined Aquifer With Infiltration h h Max Flow hAhA hBhB Water Table Ground Surface Bedrock N, Infiltration L x Steady Flow Constant K

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Steady Flow in an Unconfined Aquifer With Infiltration h h Max Flow hAhA hBhB Water Table Ground Surface Bedrock N, Infiltration L x

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h h Max Flow hAhA hBhB Water Table Ground Surface Bedrock N, Infiltration L x Steady flow in an unconfined aquifer with infiltration

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Example (Embankment) Given L = 3000 m K = 20 m/day h A = 30 m h B = 20 m N = 500 mm/yr Find: Flow to the streams and shape of water table h h Max Flow hAhA hBhB Water Table Ground Surface Bedrock N, Infiltration L x

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Example (Cont.) h h Max Flow hAhA hBhB Water Table Ground Surface Bedrock N, Infiltration L x

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Example (Drains) Subsurface drains are often used to prevent the water table elevation from increasing to an elevation where it would waterlog the roots of crops or bring unwanted salts and other chemicals in to the root zone. Steady, 1-D flow, homogeneous, isotropic aquifer, w/infiltration hdhd h Max Water Table Ground Surface Lower Confining Layer N, Infiltration L x

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Summary Confined Aquifer Flow – Continuity Equation – Steady Horizontal Flow – Transmissivity Unconfined Aquifer Flow – Continuity Equation – Steady Horizontal Flow – Steady Horizontal Flow with Infiltration – Drains

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