Hydrologic Cycle and Water Resources

Comprehensive vocabulary flashcards covering the hydrologic cycle, heat transfer in water, surface water features, groundwater hydrogeology, aquifers, and dams.

Continentality

The climatological phenomenon where regions situated farther from the ocean experience a wider and more extreme temperature range than coastal areas, which are moderated by the ocean.

Sea Breeze and Land Breeze

Local coastal wind systems driven by differences in land and ocean temperatures; air rises over the warmer surface (over land during the daytime, and over the sea at night).

Specific Heat Capacity (Water)

The quantity of heat energy required to raise the temperature of $1\,\text{g}$ of water by $1^\circ\text{C}$. Water has the highest specific heat capacity of any liquid, causing it to heat up and cool down slowly.

Sensible Heat

The heat energy required to alter the temperature of a substance without producing a phase change.

Latent Heat

The heat energy absorbed or released by a substance during a phase change (such as evaporation or freezing) while its temperature remains constant.

Calorie

A unit of heat energy defined as the amount of heat needed to raise the temperature of $1\,\text{gram}$ of water by $1^\circ\text{C}$; equal to $4.184\,\text{Joules}$ ($\text{J}$).

Rivers and Streams

Natural channelized watercourses where water flows downslope under the influence of gravity.

Lakes

Standing bodies of water situated on land; natural varieties are geologically short-lived features.

Reservoirs

Artificial lakes or pools of water created and retained behind engineered dams.

Wetlands

Shallow standing bodies of water in which emergent vegetation grows above the water level.

Natural Eutrophication

The natural, slow aging process taking place over centuries during which a lake accumulates sediment and nutrients until it fills in completely.

Cultural Eutrophication

The rapid nutrient enrichment of a water body over decades caused by human activities (such as agricultural fertilizer runoff and sewage disposal), which stimulates plant overgrowth followed by oxygen depletion by decomposers.

Watershed

The entire land area drained by a river and its tributaries; also referred to as a drainage basin or catchment.

Watershed Divide

A topographic high ridge or boundary that separates adjacent watersheds or drainage basins.

100-Year Flood

A flood event with a magnitude that has a $1/100$ (or $1\%$) statistical probability of occurring in any single year.

Stream Gauge

A monitoring station installed along a watercourse to measure and record stream stage, flow elevation, and discharge over time.

Flash Flood

A sudden, rapid elevation of stream water levels resulting from excessive rainfall, ground impermeability/saturation, or dam failures.

Stormwater

Rainfall or snowmelt that flows overland across developed impervious surfaces (such as roads, parking lots, roofs, and lawns) instead of soaking into the soil.

Green Infrastructure

Engineered systems designed to collect and retain stormwater on-site to permit natural infiltration into the ground, reducing downstream flood hazards.

Rain Garden

A bioretention depression containing sand and gravel filtration layers designed to hold stormwater temporarily, trap litter, sorb contaminants, and permit slow percolation into the subsurface.

Permeable Pavers

Specialized ground surfacing materials designed with openings or porosity that enable stormwater to percolate down into the underlying sand and gravel rather than generating runoff.

Groundwater

Water present beneath the land surface held within pore spaces, fractures, and voids in rock and sediment.

Water Table

The subsurface boundary separating the upper unsaturated zone (where pores contain air and film water) from the lower saturated zone (where all pore spaces are filled with water).

Recharge

The hydrological process through which surface water infiltrates downward through soil and rock to replenish groundwater supplies.

Discharge (Groundwater)

The emergence of groundwater to become surface water, occurring along stream channels, lake beds, or springs.

Spring

A natural surface emergence that occurs where the water table intersects the ground surface, resulting in the localized discharge of groundwater.

Gaining Stream

A stream channel whose bed lies below the local water table, receiving groundwater discharge into its flow.

Losing Stream

A stream channel whose bed lies above the water table, resulting in the loss of surface water as it recharges the underlying groundwater.

Porosity

The measure of void or open pore space relative to the total volume within a rock or sediment.

Permeability

The capacity of a porous rock, sediment, or soil to transmit fluids, determined by how well connected its internal void spaces are.

Confining Unit

A low-porosity and low-permeability geologic layer (such as clay or dense rock) that restricts or impedes the vertical movement of groundwater; also termed an aquitard or aquiclude.

Unconfined Aquifer

An aquifer whose upper boundary is the water table and is not restricted above by an impermeable confining bed.

Confined Aquifer

An aquifer bounded above and below by low-permeability confining layers, featuring a restricted recharge area and higher protection from surface contamination.

Piezometric Surface

An imaginary level to which pressurized water in a confined aquifer would naturally rise if tapped and unrestricted by confining beds; also known as the potentiometric surface.

Artesian Well

A well tapping a confined aquifer in which groundwater rises under hydrostatic pressure above the top of the aquifer; if the wellhead is below the piezometric surface, water flows freely without pumping.

Drawdown

The vertical drop or lowering of the water table elevation when well pumping rates exceed natural recharge rates.

Cone of Depression

A localized, conical depression in the water table that develops immediately surrounding an actively pumped groundwater well.

Groundwater Mining

The unsustainable extraction of groundwater at rates exceeding the natural rate of replenishment or recharge.

Subsidence

The settling, sinking, or downward compaction of the land surface caused by the loss of fluid pore pressure following excessive groundwater extraction.

Saltwater Intrusion

The movement of saline water into a freshwater coastal aquifer when overpumping lowers the freshwater table and reverses natural seaward gradients.

Ghyben-Herzberg Principle

A hydrostatic principle describing the freshwater-saltwater boundary in coastal aquifers, expressed as $z = 40 \times h$, where every $1\,\text{ft}$ drop in water table height ($h$) causes a $40\,\text{ft}$ rise in the underlying saltwater interface ($z$).

Dam

A barrier built across a flowing stream or river that restricts flow to create a reservoir for purposes such as water storage, flood defense, navigation, irrigation, and power.

Hydroelectric Power

Renewable electricity produced by releasing water from an elevated reservoir through an intake and penstock to rotate a turbine connected to a generator.

Kelly Barnes Dam

An earthen dam in Toccoa Falls, Georgia, that failed on November 6, 1977, resulting in 39 deaths and motivating the establishment of federal dam inspection initiatives.