Importance of Water, Hydrologic Cycle, and Water Ecology

A structured vocabulary flashcard set covering the importance of water, the hydrologic cycle, chemical and physical water properties, biological interactions, watershed dynamics, and stream geomorphology based on the lecture notes.

Hydrologic Cycle

The natural process describing where water is stored on Earth and how it moves across the atmosphere, oceans, land surface, and underground in gas, liquid, and solid states.

Earth's Water Storage

The distribution of global water where oceans store $96.5\%$, freshwater accounts for $2.5\%$, and only $1\%$ of total global water is usable by humans.

Residence Time

The average amount of time a water molecule spends in a specific Earth reservoir, ranging from $1\,\text{week}$ in biospheric water to up to $10{,}000\,\text{years}$ in deep groundwater.

Evapotranspiration

The combined processes of evaporation from land and water surfaces plus transpiration from plant leaves that return moisture to the atmosphere.

Infiltration

The process of water filtering into the soil, which influences surface water availability and directly drives runoff.

Water Chemistry

The study of solutes and suspended substances contained within water.

Cohesion

The intermolecular attraction that causes water molecules to stick to each other, generating high surface tension.

Adhesion

The property of water molecules adhering to other surfaces, facilitating fluid movement through biological systems.

Capillary Action

The movement of water through soil, plants, and organism bodies driven by cohesive and adhesive forces.

Alkalinity

The capacity of water to buffer or resist changes in pH when an acid or base is added, determined by minerals such as limestone and granite.

Conductivity

A measure of dissolved ions in water, directly related to salinity and total dissolved solids (TDS).

Hypoxia

An aquatic state of depleted dissolved oxygen caused by excess nutrient runoff, phytoplankton blooms, and high rates of microorganism respiration.

Water Hardness

A measure of calcium and magnesium concentration in water, categorized into hard water (high mineral levels) and soft water (low mineral levels).

Thermal Inertia

The ability of water to buffer biological systems against rapid temperature fluctuations due to its high specific heat capacity.

Buoyancy

The upward force exerted on an object by water or other fluids, equal to the weight of the fluid displaced by the object.

Viscosity

A fluid's measure of thickness or resistance to deformation, influenced by fluid state, temperature, and pressure, and measured in centipoise ($\text{cp}$).

Hydrolysis

A chemical reaction in which water acts as a reactant to break down larger molecules into smaller ones by cleaving chemical bonds.

Condensation Reaction

A chemical reaction (the reverse of hydrolysis) in which two molecules combine into a single molecule, producing water as a byproduct.

Lipid Bilayer

A thin polar membrane made from phospholipids that forms boundaries around cells and organelles to regulate molecule movement.

Biological Nutrient Cycling

The movement, dissolution, and biological recycling of essential elements—including carbon, nitrogen, phosphorus, oxygen, and sulfur—through ecosystems.

Water Ecology

The study of organisms and their interactions within aquatic environments.

Watershed

An area of land that catches precipitation and drains all water and surface runoff into a common receiving body of water.

Impervious Surfaces

Artificial structures (such as parking lots) that prevent water from percolating into the soil, forcing all rainfall to become surface runoff.

Ephemeral Stream

A stream channel that experiences water flow only during and immediately following rainfall events.

Intermittent Stream

A stream that flows seasonally during wet periods, often receding into isolated pools during dry seasons.

Perennial Stream

A stream channel that flows continuously year-round, sustained primarily by groundwater base flow.

Headwaters

The upper portion of a watershed located at steep, high elevations, characterized by high stream energy, turbulent flow, and specialized aquatic life.

Riffle

A shallow, fast-flowing stream segment with exposed cobbles that break the surface of the water.

Pool

A deep, slow-flowing segment of a stream channel typically found along outside bends.

Impoundment

The damming of a river or stream to store water, which alters natural flow regimes, reduces downstream sediment transport, and impacts aquatic habitats.