ERS Exam 4 Surface Water

What type of water flow is smooth, with parallel flow lines and minimal energy loss?

Laminar flow

What type of water flow is chaotic and characterized by energy-consuming eddies?

Turbulent flow

What is a hydrograph?

A graph plotting a river's discharge versus time

What information does the shape of a hydrograph provide?

Information on the characteristics of the drainage basin

In a river's channel flow, what is the term for water contributed from long-term sources like groundwater and wetlands?

Baseflow

On a short-term basis, how does baseflow typically behave?

It is relatively constant

What is the term for water that reaches a stream from a rain event via overland or subsurface flow?

Stormflow

What is river discharge (Q)?

The volume of water that flows down a river per unit time

What is the formula for calculating discharge (Q) in an open channel?

Discharge (Q) = Cross-sectional Area (A) * Velocity (V)

What specific river data is used to forecast flood frequency?

The maximum annual discharge

What does the Recurrence Interval (R.I.) of a flood represent?

The average time between events equal to or greater than a specific discharge rate

What is the formula used to calculate the Recurrence Interval (R.I.)?

R.I.=(n+1)/Rank, where n is the total number of measured years

How is the annual probability of exceeding a maximum discharge rate calculated?

It is calculated as 1/R.I. (Recurrence Interval)

What is the primary factor that determines stream velocity?

The hydraulic gradient, also known as the stream slope

Define 'stream competence'

The maximum size of the material that a stream can transport

Define 'stream capacity'

The total mass of material that a stream can carry

Which stream type contains intertwined channels flowing around sand and gravel bars?

Braided streams

Sediment that is 'pushed' along the bottom of a stream is known as the _____

bed load

What is the term for sediment that is carried by the water itself, not in contact with the riverbed?

Suspended load

The process where sediment 'bounces' along the bottom of a stream is called _____

saltation 

What is the general term for all sediment that a stream transports and deposits?

Alluvium 

What are four characteristics of braided streams?

Steep slope, high energy, high competence, and large width

Which stream type is characterized by a sinuous path?

Meandering streams

In a meandering stream, where does erosion primarily occur?

Along the outside bends of the meanders

In a meandering stream, where does deposition primarily occur?

On the inside bends of the meanders

What landform can be created when meander loops are cut off from the main river?

Oxbow lakes

What are the energy and slope characteristics of meandering streams?

Lower energy and lower slope

What are the competence and capacity characteristics of meandering streams?

High competence and high capacity

List three primary purposes of building dams

Flood control, energy production, and as a drinking water source

How do dams negatively affect sediment movement downstream?

They decrease the sediment supply downstream

How does the trapping of sediment by a dam affect the reservoir itself?

It reduces the reservoir's volume over time

What is a major consequence of reduced sediment supply downstream from a dam?

Increased erosion downstream

What is the primary goal of river channelization?

To increase stream velocity and discharge

What is a major negative consequence of channelization further downstream?

It increases flooding downstream

What is the function of a retention pond?

To trap water and sediments

What are levees?

Raised river banks, which can be natural or human-made

How do human-made levees affect flooding?

They increase downstream flooding

What problem can occur if a levee is overtopped by floodwaters?

It traps the water, preventing it from draining back into the river

What is the defining characteristic of a lake?

A water-filled depression surrounded by land and not connected to the ocean

What is the primary difference between a lake and a surface-water reservoir?

A reservoir is artificial (human-made)

Over time, lakes slowly accumulate _____ and _____ solids

mineral; organic

Term: Oligotrophic Lake

A lake with high dissolved oxygen, low nutrients, low plant productivity, and clear water

Term: Eutrophic Lake

A lake with low dissolved oxygen, high nutrients, high plant productivity, and cloudy water

What is cultural eutrophication?

The acceleration of the eutrophication process by human activities

What is the primary cause of cultural eutrophication?

Excessive nutrient loading (e.g., nitrogen and phosphorus)

List three sources of excessive nutrients that cause cultural eutrophication

Sewage, fertilizers, and phosphate soaps

How does cultural eutrophication lead to fish kills?

Decaying organic matter produced at the surface consumes oxygen in deeper water, leading to oxygen depletion

What fundamental property of water causes lakes to stratify?

Differences in water density

Name the two types of stratification mentioned in the text

Chemical stratification (due to salinity) and thermal stratification (due to temperature)

What term describes lakes that have constant salinity and stratify by temperature?

Holomictic lakes

What is a dimictic lake?

A type of holomictic lake that turns over twice a year due to seasonal temperature changes

What is the defining characteristic of a meromictic lake?

They have high salinity bottom waters that prevent mixing

In a stratified lake, what is the name for the upper, less dense layer?

The epilimnion

In a stratified lake, what is the name for the boundary separating warm and cold water?

The thermocline

In a stratified lake, what is the name for the lower, denser layer?

The hypolimnion

Why does a pond freeze from the top down?

Because ice (and water at 0°C) is less dense than liquid water at 4°C

What are two effects of a layer of ice on a pond?

It insulates the pond and limits oxygen exchange with the atmosphere

What kind of stratification occurs in a frozen lake?

Cold water (near 0°C) stratifies over warmer, denser water (at 4°C)