Freshwater Hydrology and Water Cycles

Vocabulary flashcards covering topics in freshwater hydrology, unique water properties, phase changes, watershed dynamics, soil water budgets, and hydrographs.

Polar Molecule

A molecule with an uneven distribution of electrical charges, such as water where oxygen carries a partial negative charge and hydrogen carries a partial positive charge.

Cohesion

The attraction between molecules of the same substance that helps water stay connected through movement.

Surface Tension

A property of water caused by cohesion that allows it to resist external forces that would pull its surface apart.

Adhesion

The attraction between molecules of different substances.

Capillary Action

The process where a liquid flows through a narrow space against external forces like gravity.

Solvent

A substance capable of dissolving other substances by surrounding charged ions, atoms, or molecules.

Hydrophilic

Water-loving; describes polar substances that dissolve easily in water.

Hydrophobic

Water-fearing; describes non-polar substances that do not dissolve in water.

Crystalline Structure

An organized structural arrangement formed by hydrogen bonds as water freezes, pushing molecules farther apart and making ice less dense than liquid water.

Reservoir

A location within the Earth system where water is stored.

Evaporation

The process that transfers liquid water from Earth's surface into the atmosphere.

Transpiration

The process that transfers water from the soil or plants into the atmosphere.

Evapotranspiration

The combined total amount of water returned to the atmosphere through evaporation and transpiration.

Advection

The horizontal transport of water vapor through the atmosphere by moving air.

Condensation

The phase change where atmospheric conditions cause water vapor to turn into liquid water droplets.

Precipitation

Water returning to the Earth's surface or atmosphere through rain or snow.

Sublimation

The phase change when water moves directly from a solid state to a gaseous state.

Desublimation

The phase change when water vapor turns directly into ice, also referred to as deposition.

Infiltration

The process by which precipitation water reaching the land enters into the soil.

Groundwater Recharge

Water that percolates downward far enough to replenish groundwater reserves.

Adiabatic Cooling

The cooling process that occurs when air rises, expands, and experiences decreasing surrounding air pressure.

Condensation Nuclei

Tiny airborne particles on which water vapor condenses at a dewpoint to form cloud droplets or ice crystals.

Vaporization

The process where liquid water absorbs energy, breaking intermolecular attractions to transition into a gaseous state.

Latent Heat

Energy absorbed or released during a phase change while temperature remains constant.

Watershed

An area of land (also called a drainage basin) where all water drains toward a common outlet such as a stream, river, lake, or reservoir.

Watershed Divide

A boundary defined by elevation that separates adjacent watersheds and determines drainage direction.

Percolation

The slow movement of liquid through a porous substance or filter.

Water Budget

A calculation tracking total inputs, outputs, and changes in water storage within a watershed using the formula $\text{Inputs} - \text{Outputs} = \text{Change in Storage}$.

Soil Water Budget

A measurement tracking water availability specifically in the plant root zone, usually $1\text{ meter}$ deep.

Potential Evapotranspiration ($E_p$)

The total monthly amount of water that could evaporate and transpire if an unlimited water supply were available, representing environmental water demand.

Actual Evapotranspiration ($E_a$)

The actual amount of water that evaporates and transpires based on current water availability.

Permeable Surface

A surface such as soil or vegetated land that allows natural water infiltration into the ground.

Impermeable Surface

A surface such as roads, roofs, or parking lots that prevents water from infiltrating into the ground.

Hydrograph

A graph tracking stream discharge—volume of water per unit of time—over a period following a storm event.

Stream Discharge

The volume of water flowing through a stream over a specific period of time.

Peak Discharge

The maximum stream discharge or water level reached following a storm event.