Hydrogeology vs Hydrology: What's the Difference Between Them?

Study Notes

Hydrogeology vs. Hydrology

Hydrogeology is the branch of geology that deals with the occurrence, distribution, and effect of groundwater.
Hydrology is the science of water occurrence, movement, and transport.

Hydrologic Cycle

The hydrologic cycle is the natural process of recycling water from the atmosphere to the earth and back to the atmosphere again.
It begins with evaporation, where water rises into the sky from open bodies of water and near-surface soil.
Water in the sky eventually falls to the earth as precipitation (sleet, hail, snow, rain, dew).
Precipitation that falls onto land becomes the source of all surface water.
A significant portion of surface water soaks into the ground, recharging groundwater.

Processes in Hydrologic Cycle

Evaporation: water rises into the sky from open bodies of water and near-surface soil.
Condensation: water vapor in the atmosphere cools and turns into liquid or ice.
Precipitation: any form of solid or liquid water that falls from the atmosphere to the earth's surface.
Transpiration (Biological Processes): plants draw water out of the ground through their roots.
Interflow: water infiltrated but not below the water table.
Groundwater flow: water infiltrated and below the water table.
Baseflow: groundwater flow that reaches a stream.
Overland flow: water on the surface.

Precipitation

Precipitation is the single strongest variable driving hydrologic processes.
It is formed by water vapor in the atmosphere.
Causes of precipitation include:
Frontal precipitation: occurs when warm or light air mass meets a cold or heavy air mass.
Convective precipitation: air expands when heated by solar energy and becomes lighter than the air around it.
Orographic precipitation: air currents force air masses to rise over hills and mountains.

Hillslope Hydrology

Runoff processes include:
Horton overland flow
Subsurface stormflow
Return flow
Groundwater flow
Many processes occur simultaneously, and shifts can occur between processes in space and time.
Antecedent wetness conditions are important, and watershed characteristics play a central role.

Runoff Generation

Horton overland flow occurs when rainfall intensity exceeds infiltration capacity.
It was once thought to be the only mechanism of runoff generation.
Subsequent work showed the role of partial source area, where saturation overland flow is produced.

Subsurface Stormflow

Lateral flow through soil above conductivity contrast.
Consists of both slower matrix flow and faster macropore flow.

Saturation Overland Flow

Direct rainfall onto saturated areas.
Return flow from saturated soils in topographic lows and along valley.

Description

Test your knowledge of hydrogeology and hydrology, two related but distinct fields of study. Hydrogeology focuses on groundwater, while hydrology examines the broader water cycle. See how well you can distinguish between these two important concepts.