Rivers & Groundwater

aquifer

Any rock or sediment through which groundwater flows easily

Bed Load

Big sediments that are rolled or dragged along the bottom of a river.

cutbank

eroded stream bank on the outside of a meander curve

Delta

a fan-shaped deposit of sediment that forms when a river flows into a non-flowing large body of water, such as a lake, ocean or inland sea.

Deposition

The process of laying down of sediment.

Dissolved Load

Sediment that is dissolved into the water and transported within the current of the stream.

Divide

A ridge of land that separates one drainage basin from another.

Drainage Basin

All of the land area where rainfall will run off or infiltrate into a river system, bounded by divides. Same as a watershed.

Flood Plain

a flat plain next to a river that is made of fine river sediment and is subject to periodic flooding

Gradient

the slope of a river channel or landscape over a certain distance. Expressed by the equation: change in elevation/distance

groundwater

water beneath the surface stored and flowing in pore space in rock/sediment.

Meander

a bend in the channel of a river. Characteristic formation when gradient decreases and erosion is mostly side-to-side vs. downcutting.

oxbow lake

A crescent-shaped body of water formed when sediments deposited by a river during flood stage cut off a meander from the river.

permeability

The ability of a rock or sediment to let fluids pass through its open spaces, or pores.

Point Bar

crescent shaped pile of sediment built up by river deposition on the inside of a meander

River System

A river and all of its tributaries

Suspended Load

describes the transportation of clay or silt sized sediment carried within the current of the river

Tributary

a smaller river that flows into a bigger river

water table

the top of the zone of saturation

zone of aeration

the zone in an aquifer above the water table where the pore spaces are filled with air

zone of saturation

the zone in the aquifer below the water table where all open spaces are filled with water

mouth

place where a river empties into another body of water

head

a stream's point of origin

Runoff

water that flows over the ground surface rather than soaking into the ground

Erosion

Processes by which rock, sand, and soil are broken down and carried away

trunk stream

a major river, fed by a number of fairly large tributaries; the main stream in a river system

watershed

See drainage basin definition

meander scar

Dried up oxbow lake

Velocity

the speed of an object in a particular direction

young river

a fast-moving, relatively straight river that down cuts in a "V" shape and has waterfalls and rapids

middle-aged river

a river's journey, when it gets wider, slows down, and meanders start to form, creating point bars and cutbanks

old river

-slow-moving, flat river

Continental Divide

mountain ridge that separates river systems flowing toward opposite sides of a continent

triple divide peak

location where two continental divides touch

river age/stage

section of a river that is defined by certain characteristics

lifting

the carrying of sediment in a river that is above the bed of the river

abrasion

The grinding away of rock by other rock particles carried in water, ice, or wind

dissolving

a physical change in which particles of a substance are separated by water particles

saltation

Small pebbles and stones are bounced along the river bed

Porosity

Percentage of open spaces between grains in a rock.

impermeable layer

A layer of material (such as clay or shale) in an aquifer through which water does not pass.

capillary fringe

the thin subsurface layer in which water molecules seep up from the water table by capillary action to fill pores

ordinary well

A well that is dug or drilled down to the water table

spring

A flow of groundwater that emerges naturally at the ground surface

artesian formation

A sandwich of permeable and impermeable rocks

geyser

A fountain of water and steam that builds up pressure underground and erupts at regular intervals.

permeable

penetrable; porous; allowing liquids or gas to pass through

impermeable

Impassable, not allowing passage through (such as by a liquid)