Chapter 4 Fetter Principles of groundwater flow
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Transcript of Chapter 4 Fetter Principles of groundwater flow
Principles of Groundwater Flow
Ayat Ate f MahdyHeba harara
Al-Azhar University-Gaza Master Program of Water and Environmental
Science
Forms of energy that ground water possesses
Mechanical Energy of a fluid
Bernoulli Equation
Hydraulic head
Head in water with variable density
Force potential and hydraulic head
Darcy law
Reynolds number
Specific discharge and Average Linear Velocity
Equations of Ground-Water Flow
Gradient of Hydraulic Head
Flow net:flow net must show boundaries:
Boundary condition is important when the effect of transient stresses reach the boundary 1.Physical boundaries (impermeable rock formation) 2.Hydraulic boundary ( groundwater divide , partly aquifer penetrating water bodies and streamlines )3.No flow boundary (fault zones and salt water interface)
Formula:
,
q = K *p* h /f
• where: q= = total discharge per unit width of aquifer (L3/T)
• K = hydraulic conductivity
• p = number of flow tubes
• h = total head drop • f = number of squares,
covering length of flow
Equations of groundwater flow A) Steady flow in a confined aquifer - Flow implies that the aquifer has a gradient (Remember: water flows downhill)
B) Steady flow in an unconfined aquifer: Aquifer isn't always fully saturated.Gradient is not constant now.Gradient increases in the direction of flow .
2 problems: - Equation for this sloping surface is much more complicated - Also: recharge from the surface affects the gradient
- The solution: make some assumptions about boundary conditions, calculate discharge through a section of the aquifer:
The equation for discharge (Dupuit equation):
Sieve analysis: