Chapter 5: Running Water and Groundwater

Hydrologic cycle

the sum total of all processes in which water moves from the land and ocean surface to the atmosphere and back in form of precipitation.

Evaporation

the process by which liquid water changes into water vapor (gas), is how water enters the atmosphere from the ocean and, to a much lesser extent, from the continents.

Infiltration

A portion of the water soaks into the ground, slowly moving downward, then moving laterally, and finally seeping into lakes, streams, or directly into the ocean.

Runoff

occurs when there is more water than land can absorb. The excess liquid flows across the surface of the land and into nearby creeks, streams, or ponds. It can come from both natural processes and human activity.

Transpiration

the water that soaks into the ground is absorbed by plants, which then release it into the atmosphere.

Evapotranspiration

the quantity of water that is removed from a surface due to the processes of evaporation and transpiration

Drainage basin

the land area that contributes water to a body of water such as river, lake, or ocean

Divide

The drainage basin of one stream is separated from the drainage basin of another by an imaginary line

Continental divide

splits whole continents into enormous drainage basins.

Sediment production

An area where most of the sediment is derived, is located in the headwater region of the river system.

Sediment transport

The process wherein sediments acquired by a stream is transported through the channel network along sections

Sediment deposition

A process in wherein sediments carried by the stream or channel settles down.

Dendritic pattern

This pattern of irregularly branching tributary streams resembles the branching pattern of a deciduous tree. Forms where the underlying material is relatively uniform.

Radial pattern

When streams diverge from a central area like spokes from the hub of a wheel

Rectangular pattern

exhibits many right-angle bends. This pattern develops when the bedrock is crisscrossed by a series of joints and/or faults. Because these structures are eroded more easily than unbroken rock, their geometric pattern guides the directions of valleys.

Trellis pattern

a rectangular drainage pattern in which tributary streams are nearly parallel to one another and have the appearance of a garden trellis. This pattern forms in areas underlain by alternating bands of resistant and less-resistant rock.

Laminar flow

the water moves in roughly straight-line paths that parallel the stream channel.

Turbulent flow

streamflow is usually turbulent, with the water moving in an erratic fashion that can be characterized as a swirling motion.

Factors affecting flow velocity

Gradient, Channel size, shape, and roughnes, and discharge

Gradient

The slope of a stream channel expressed as the vertical drop of a stream over a specified distance

Channel size, shape, and roughness

These factors of the channel affect the amount of friction.

Discharge

the volume of water flowing past a certain point in a given unit of time. It is usually measured in cubic meters per second or cubic feet per second, is determined by multiplying a stream's crosssectional area by its velocity.

Longitudinal profile

a cross-sectional viewof a stream from its source area (headwaters to mouth)

Pothole

a circular or cylindrical hole in the riverbed which is produced by force of water and abrasion. It is formed when a circular current of water carrying small pebbles and sediment begins to wear away a rock surface.

Dissolved load

the portion of a stream's total sediment load that is carried in solution

Suspended load

the portion of its sediment uplifted by the fluid's flow in the process of sediment transportation.

Bed load

refers to the sediment which is in almost continuous contact with the bed, carried forward by rolling, sliding or hopping.

Settling velocity

the speed at which a particle falls through a still fluid.

Saltation

the bouncing of particles as they are picked up, carried along, and dropped repeatedly by flowing water.

Capacity

the maximum load of solid particles a stream can transport per unit of time. The greater the discharge, the greater the stream's capacity for hauling sediment

Competence

a measure of a stream's ability to transport particles based on size rather than quantity.

Sorting

describes how fine to coarse grain sediments are distributed (settle)

Alluvium

general term for sediment deposited by streams

Bedrock channels

Stream channels whose beds and banks are made of solid rock

Alluvial channels

Stream channels that are composed of loosely consolidated sediment (alluvium)

Meandering channel

Streams that transport much of their load in suspension generally move in sweeping bends

Meander

When water flows in a curvy, bendy path, like a snake

Cut bank

the outside bank of a curve or meander in a water channel (stream), which is continually undergoing erosion.

Point bar

depositional feature made of alluvium that accumulates on the inside bend of streams and rivers below the slip-off slope.

Cutoff

the river may erode through the narrow neck of land, forming a new, shorter channel segment

Oxbow lake

Small lake located in an abandoned meander loop of a river channel. It is generally formed as a river cuts through a meander neck

Braided channel

Streams consist of a complex network of converging and diverging channels that thread their way among numerous islands or gravel bars

Stream valley

Consists of not only the channel but also the surrounding terrain that directly contributes water to the stream. Thus, it includes the valley bottom

Valley bottom

The lower, flatter area that is partially or totally occupied by the stream channel, and the sloping valley walls that rise above on both sides.

Base level

the lowest elevation to which a stream can erode its channel. Essentially this is the level at which the mouth of a stream enters the ocean, a lake, or another stream.

Ultimate base level

Pertains to sea level because it is the lowest level to which stream erosion could lower the land.

Temporary or local base level

Include lakes, resistant layers of rock, and main streams that act as base levels for their tributaries.

Floodplain

The flat land area adjacent to a stream, composed of unconsolidated sedimentary deposits and when a river overflows its banks during flood stage.

Incised meander

meanders which are particularly well developed and occur when a river's base level has fallen giving the river a large amount of vertical erosion power, allowing it to downcut.

Bar

an elevated region of sediment (such as sand or gravel) that has been deposited by the flow.

Delta

low-lying, almost flat landform, composed of sediments deposited where a river flows into a lake or an ocean and forms where a sediment-charged stream enters the relatively still waters of a lake, an inland sea, or the ocean

Distributary

a stream that branches off and flows away from a main stream channel

River bifurcation

occurs when a river flowing in a single stream separates into two or more separate streams (called distributaries) which then continue downstream.

Natural levee

a deposit of sand or mud built up along, and sloping away from, either side of the flood plain of a river or stream and are embankments that formed naturally after a river floods and recedes.

Back swamp

the marshy tract behind the natural levees usually formed due to flood waters which are unable to escape.

Yazoo tributary

A tributary stream that cannot enter a river because levees block the way often has to flow parallel to the river until it can breach the levee.

Alluvial fan

A cone-shaped feature in the landscape where silt, gravel, sand, and sometimes boulders, have been deposited. Typically develop where a high-gradient stream leaves a narrow valley in mountainous terrain and comes out suddenly onto a broad, flat plain or valley floor

Flood

occurs when the flow of a stream becomes so great that it exceeds the capacity of its channel and overflows its banks.

Artificial levees

are earthen mounds built on the banks of a river to increase the volume of water the channel can hold.

Flood-control dams

are built to store floodwater and then let it out slowly.

Channelization

involves altering a stream channel in order to speed the flow of water to prevent it from reaching flood height. This may simply involve clearing a channel of obstructions or dredging a channel to make it wider and deeper.

Zone of Saturation

a zone where all the open spaces in sediment and rock are completely filled with water.

Groundwater

water that exists underground in saturated zones beneath the land surface.

Water table

the boundary between the unsaturated zone and the saturated zone underground.

Unsaturated Zone

The area above the water table where the soil, sediment, and rock are not saturated

Porosity

the percentage of the total volume of rock or sediment that consists of pore spaces

Permeability

a measure of the ability of a material (such as rocks) to transmit fluids.

Aquitard

Impermeable layers such as clay that hinder or prevent water movement

Aquifer

Permeable rock strata or sediments that transmit groundwater freel

Spring

Whenever the water table intersects the ground surface and find an opening, a natural flow of groundwater emerges

Perched water table

an accumulation of groundwater that is above the water table in the unsaturated zone. The groundwater is usually trapped above an impermeable soil layer, such as clay, and actually forms a lens of saturated material in the unsaturated zone.

Hot spring

a spring that is produced when geothermally heated groundwater emerges from the Earth's crust.

Geyser

Intermittent fountains in which columns of hot water and steam are ejected with great force, often rising 30 to 60 meters (100 to 200 feet) into the air,

Well

a hole bored into the zone of saturation.

Drawdown

Whenever a substantial amount of water is withdrawn from a well, the water table around the well is lowered.

Cone of depression

A depression in the groundwater table or potentiometric surface that has the shape of an inverted cone and develops around a well from which water is being withdrawn. The slopes of the cone become increasingly steep the closer they are to the well.

Artesian system

refers to a situation in which groundwater rises in a well above the level where it was initially encountered.

Artesian well

When the pressure surface is above the ground level and a well is drilled into the aquifer, this feature will be created.

Artesian spring

discharge under pressure due to confined conditions in the underlying aquifer. They are also called ascending or rising springs.

2 conditions for artesian system to occur

(1) Water must be confined to an aquifer that is inclined so that one end is exposed at the surface, where it can receive wate(2) aquitards both above and below the aquifer must be present to prevent the water from escaping.

Confined Aquifer

an aquifer below the land surface that is saturated with water. Layers of impermeable material are both above and below the aquifer, causing it to be under pressure so that when the aquifer is penetrated by a well, the water will rise above the top of the aquifer.

Cavern

created at or below the water table, in the zone of saturation. Here acidic groundwater follows lines of weakness in the rock, such as joints and bedding planes. As time passes, the dissolving process slowly creates cavities and gradually enlarges.

Stalactite

icicle-like pendants hang from the ceiling of a cavern and form where water seeps through cracks above.

Stalagmite

Formations that develop on the floor of acavern and reach upward toward the ceiling

Karst topography

A landscape that is characterized by numerous caves, sinkholes, fissures, and underground streams. Usually forms in regions of plentiful rainfall where bedrock consists of carbonate-rich rock, such as limestone, gypsum, or dolomite, that is easily dissolved.

Sinkhole

irregular terrain punctuated with many depressions or holes in the ground caused by some form of collapse of the surface layer.