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: