Guided Notes about Groundwater Section 10.1

Infiltration Much of the precipitation that falls on land enters the ground through the process of infiltration and becomes groundwater.

Groundwater slowly moves through the ground, eventually returns to the surface through springs, and then flows back to the oceans.

Porosity is the percentage of pore space in a material Porosity is the percentage of pore space in a material. The porosity of well-sorted sand is typically 30 %.

Differentiate between the zone of saturation and aeration: The zone of saturation is the depth at which groundwater completely fills all the pores of the rock. The zone of aeration is above the zone of saturation, and is moist, but the pores contain mostly air.

The water table is the upper boundary of the zone of saturation.

Gravitational water is water that trickles downward due to gravity, while capillary water is water that is drawn upward from the water table and is held in the pore spaces of rock as a result of surface tension.

The topography of the water table follows the topography of the land above it. The water table slopes toward valleys and forms hills under topographic hills.

Groundwater flows downhill in the direction of the slope of the water table. Downhill movement is slow because water has to squeeze through numerous tiny pores in the subsurface material.

Permeability Permeability is the ability of a material to let water pass through it. Five permeable materials are sand, gravel, sandstone, limestone, and highly fractured bedrock.

Fine-grained materials typically have low permeabilities Fine-grained materials typically have low permeabilities. Examples of impermeable materials are silt, clay, and shale.

Why does the flow velocity of groundwater depend upon the slope of the water table? Because the force of gravity pulling the water downward is greater when the slope of the water table surface is steeper.

Although the flow velocity of groundwater is proportional to both the slope of the water table and the permeability of the material through which it flows, permeability is the major factor. Flow velocities through permeable materials are always higher than those through impermeable materials, regardless of the slope of the water table.

What is an aquifer? An aquifer is a permeable layer of bedrock through which most groundwater flows.

What is an aquiclude? An aquiclude is an impermeable layer that is a barrier to groundwater flow.