4: Groundwater Flow

Aquifer

a body of rock and/or sediment that holds groundwater.

Confined aquifers

an aquifer below the land surface that is saturated with water

unconfined aquifer

an aquifer whose upper water surface (water table) is at atmospheric pressure

Groundwater

transported through aquifers

gravity and pressure

Groundwater is transported through aquifers because of two main reasons:

gravity

In unconfined aquifers, water always flows from high points to low points because of?

Aquifer

a saturated geological formation that contains and transmits significant quantities of water under normal field conditions.

Aquiclude

a formation that may contain water but does not transmit significant quantities of water.

Aquitard

a formation with relatively low permeability

Piezometric or potentiometric surface

the height to which water will rise in a well.

Darcy’s law

states the principle which governs the movement of fluid in the given substance

permeability

measuring the inter-connectivity

Hydraulic conductivity

physical property which measures the ability of materials to transmit fluid through the pore spaces and fractures in the presence of applied hydraulic gradient

Hydraulic gradient

the slope of the water table; the change in water level per unit of distance along the direction of maximum head decrease

peak discharge

is defined as the volume rate of flow within a river or stream, or as the rate of flow of runoff that flows from (through) the exit point of a watershed

runoff coefficient

a dimensionless coefficient relating the amount of runoff to the amount of precipitation received

high runoff coefficient

may indicate flash flooding areas during storms as water moves fast overland on its way to a river channel or a valley floor.

aquifer thickness

Distance from a lower confining layer to an upper confining layer or to groundwater table elevation

transmissivity

Function of aquifer conductivity and thickness

Piezometric head

Sum of pressure and elevation heads

Effective porosity

Portion of the soil property that is available for fluid flow

Cone of depression

A depression in the groundwater table or potentiometric surface that has the shape of an inverted cone and develops around a well from which water is being withdrawn.

increasingly steep

The slopes of the cone become _____ the closer they are to the well.

Radius of influence

means the radial distance from the center of a pumped well to the point where there is no lowering of the water table or potentiometric surface

potentiometric surface

the edge of the cone of depression

Drawdown

a change in groundwater level due to an applied stress, caused by events such as pumping from a well or pumping from a neighbouring well.