Water Cycle and Stream Flow: Key Concepts and Graphs

Residence Time

The average length of time that a water molecule remains in a particular reservoir of the water cycle before moving to another location.

Stream Discharge

The volume of water flowing past a specific point in a stream per unit of time, usually measured in cubic meters or cubic feet per second.

Stream Order

A classification system that ranks streams based on the number and hierarchy of their tributaries, with small headwater streams being first order and larger rivers having higher order numbers.

Water Cycle

The continuous movement of water between Earth's oceans, atmosphere, land, and living organisms through processes such as evaporation, condensation, precipitation, infiltration, and runoff.

Water Cycle Reservoirs and Flows

The storage locations of water (such as oceans, glaciers, groundwater, lakes, rivers, and the atmosphere) and the pathways water moves through between them.

Hydrographs

Graphs that show how a river's discharge changes over time, often used to analyze the effects of rainfall and flooding.

Rating Curves

Graphs that show the relationship between stream water level (stage) and discharge, allowing discharge to be estimated from measured water levels.

Flood Frequency Curves

Graphs that show how often floods of different magnitudes occur based on historical records.

Unit Hydrograph

A graph showing the change in stream discharge over time produced by a specific amount of rainfall occurring over a watershed during a set time period.

Settling Velocity

The speed at which sediment particles fall through water, influenced by particle size, density, and water resistance.

Relationship Between Stream Velocity and Erosion/Deposition

Faster stream velocities increase the ability of water to erode and transport sediment, while slower velocities cause sediments to settle and be deposited.

Alluvial Fans

Fan-shaped deposits of sediment that form where a steep mountain stream flows onto a flatter plain and suddenly slows down.

Deltas

Sediment deposits that form where a river enters a standing body of water such as a lake or ocean and the water velocity decreases.

Meandering Streams

Streams that flow in winding curves or loops across a floodplain due to erosion on outer bends and deposition on inner bends.

Braided Streams

Streams with multiple interweaving channels separated by sediment bars, typically formed where sediment supply is high and water flow varies.

Flood Management Methods

Techniques used to reduce flood damage, including levees, dams, floodways, zoning regulations, wetlands protection, and improved forecasting and warning systems.