GEOL 291 Lecture Notes - Lecture 17: Hydraulic Head, The Fluid, Aquifer
13 Nov 2020
School
Department
Course
Professor
Lecture 17: Groundwater (11/5/20)
● Direction of flow told by potentiometric surface map
○ Water flows from high to low pressure - negative slope
● Groundwater flow
○ Gravity moves groundwater, but hydraulic head applies pressure to move it more
○ Darcy’s law
■ Darcy
● French civil engineer
● Public works department, conducted studies for water filtration
■ Attempted wells but they failed, focused on filtration
■ Experiment - tilted tube
■ Flow is dictated by pressure
■ Head loss: Energy lost during flow
● Friction between pore spaces
● Energy is converted to heat energy
■ Groundwater warms up as it moves but temperature is not really that measurable or
important
○Representative elemental volume: set up a proxy system of aquifer materials
■ Called a darcy column
○
○ Established empirically that the energy lost in water flowing through a permeable formation is
proportional to the length of the sediment column
■ Darcy’s velocity is proportional to the i
○
○ Q: volumetric flow rate
■ Always volume over time
○ A: cross-sectional area of flow
○ dh/dL: hydraulic gradient (no units)
Document Summary
Direction of flow told by potentiometric surface map. Water flows from high to low pressure - negative slope. Gravity moves groundwater, but hydraulic head applies pressure to move it more. Public works department, conducted studies for water filtration. Attempted wells but they failed, focused on filtration. Groundwater warms up as it moves but temperature is not really that measurable or important. Representative elemental volume : set up a proxy system of aquifer materials. Established empirically that the energy lost in water flowing through a permeable formation is proportional to the length of the sediment column. Darcy"s velocity is proportional to the i. A: cross-sectional area of flow dh/dl: hydraulic gradient (no units) Change in water level over some distance. Rate of groundwater flow is related to. Hydraulic gradient, k is a function of permeability. Calculate rate of groundwater flow: how fast groundwater is used/replenished. Groundwater flow a function of energy and hydraulic head.
