how discharge varies along the course of a stream

Discharge at any location along a stream is the product of the velocity of water (ft/sec) and the stream's cross-sectional area (in square ft). Discharge has units of cubic feet per second (cfs). The picture shows that the stream's speed varies from top to bottom and from side to side because the channel depth also varies from side to side.

Full Answer

What factors affect the discharge of a stream?

There are several factors that affect stream discharge. The velocity of the water affects it; faster water means more passes per second so more discharge. The width and depth of the river also affects it; a larger river at the same speed will have higher discharge. How do velocity and discharge affect stream erosion and deposition?

How do you calculate the discharge of a stream?

• Cd=Measured Flow RateTheoretical Flow Rate (1)
• η=σΔp12ρ¯V2 (6)
• ξ=σΔp¯Δp (7)

How do you calculate the discharge of a river?

• Peakdischarge - maximum amount of water held in the channel.
• Peak rainfall – maximum amount of rainfall (millimetres).
• Lag time - the time taken between peak rainfall and peak discharge.
• Rising limb - shows the increase in discharge on a hydrograph.
• Falling limb - shows the return of discharge to normal/base flow on a hydrograph.

More items...

How does a stream discharge?

Stage-Discharge Relationship

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How does stream discharge change?

How Does Stream Discharge Change? Generally, stream discharge doesn't change from one part of the river to the next. The same amount of water has to flow all the way down the river, otherwise you would get gaps in the river flow at one location and have the water build up at another location.

What factors determine the discharge of a stream?

How is river discharge affected by physical factors?Impermeable Rock (e.g. granite) – Water is unable to infiltrate through, resulting in more surface runoff, increasing volume of the channel and its speed.Permeable Rock – More infiltration, resulting in less surface runoff and less volume in the river.More items...

How is discharge related to stream size?

During time of high discharge the river becomes wider, deeper and rounder. As the discharge has increased the water will flow faster and have more energy.

What shows the variations in river discharge?

Variation in river discharge is generally represented by five components that organize riverine ecological processes: the magnitude, frequency, timing, duration, and rate of change of flow (Poff et al., 1997).

What causes stream discharge to change over time?

Changes Downstream Discharge increases, as noted above, because water is added to the stream from tributary streams and groundwater. As discharge increases, the width, depth, and average velocity of the stream increase. The gradient of the stream, however, will decrease.

What is discharge of a stream?

Discharge is the volume of water moving down a stream or river per unit of time, commonly expressed in cubic feet per second or gallons per day.

How are stream stage and stream discharge related?

The stage-discharge relation depends upon the shape, size, slope, and roughness of the channel at the streamgage and is different for every streamgage. The development of an accurate stage-discharge relation requires numerous discharge measurements at all ranges of stage and streamflow.

How does stream velocity affect discharge?

The increased velocity and the increased cross-sectional area mean that discharge increases. As discharge and velocity increase so do the stream's competence and capacity.

What are the factors determining the flow of a river?

The factors determining the flow of a river are 1.Volume of water 2.Rock structure 3.Slope of the terrain 4. Amount of sediments.Volume of water.Rock structure.Slope of the terrain.Amount of sediments.

Which two factors will increase the rate of a streams flow?

Flood Erosion and Deposition: As flood waters rise, the slope of the stream as it flows to its base level (e.g., the ocean or a lake) increases. Also, as stream depth increases, the hydraulic radius increases thereby making the stream more free flowing. Both of these factors lead to an increase in stream velocity.

What is stream discharge?

Discharge is the volume of water moving down a stream or river per unit of time, commonly expressed in cubic feet per second or gallons per day.

What factors affect stream quality?

The quality of river and stream water is very sensitive to anthropogenic influences (urban, industrial and agricultural activities, increasing consumption of water resources) as well as natural processes (changes in precipitation inputs, erosion, weathering of earths crustal material) degrade the surface waters and ...

What is stream discharge?

Stream discharge is the amount (volume) of water carried by a stream past a point per second. It is measured in meters cubed per second or cubic feet per second. There are several factors that affect stream discharge. The velocity of the water affects it; faster water means more passes per second so more discharge. Click to see full answer.

What is the discharge of a drainage basin?

The discharge from a drainage basin depends on precipitation, evapotranspiration and storage factors. Likewise, people ask, why is stream discharge important? Stream flow, or discharge, is the volume of water that moves over a designated point over a fixed period of time.

How does velocity affect discharge?

The velocity of the water affects it; faster water means more passes per second so more discharge. Click to see full answer. Considering this, what is used to calculate a stream's discharge? The discharge of a stream is the product of its velocity (V - length of travel per unit of time such as feet/second) times depth of the water ...

What is discharge measurement?

Discharge Measurement. Streamflow, or discharge, is the volume of water moving down a stream or river per unit of time, commonly expressed in cubic feet per second or gallons per day. Because stream discharge cannot be measured directly, it must be computed from variables that can be measured directly, such as stream depth, stream width, ...

How often do stream gauges measure stage?

A streamgage usually measures stage every 15 minutes. When intense rainfall and runoff cause a stream or river to rise quickly, however, the time intervals can be as short as every 5 minutes. The data are typically transmitted to USGS computers on a preset schedule by way of satellite—usually every 1 to 4 hours.

What is a rapid deployment gage?

Rapid-deployment gages (RDGs) are gages that are temporarily fixed on structures above streams and rivers (such as bridges) during emergencies to provide water level information when a streamgage does not exist or is damaged. Super gages are a small subset of streamgages that collect both streamflow and continuous water-quality data.

What is the USGS?

The USGS is the federal agency responsible for operating a network of about 7,000 streamgages nationwide.

What is a streamgage?

A streamgage is a structure installed beside a stream or river that contains equipment that measures and records the water level (called gage height or stage) of the stream. Streamflow (also called discharge) is computed from measured water levels using a site-specific relation (called a stage-discharge rating curve) developed from onsite water level and streamflow measurements made by USGS hydrographers. The water level and streamflow data are quality assured and made available online.

How does the Doppler effect work?

In contrast, ADCPs are hydroacoustic instruments that use the principles of the Doppler Effect to measure water velocity by sending a sound pulse into the water and measuring the change in the frequency of the sound pulse reflected back to the ADCP by sediment or other particulates being transported in the water.

What is streamflow measurement?

Although streamflow is computed from measurements of other variables, the term “streamflow measurement” or “discharge measurement” is generally applied to the final result of the calculations. Diagram of channel cross section with subsections.

What is river discharge?

River discharge is the volume of water flowing through a river channel. This is the total volume of water flowing through a channel at any given point and is measured in cubic metres per second (cumecs). The discharge from a drainage basin depends on precipitation, evapotranspiration and storage factors. Drainage basin discharge = precipitation – evapotranspiration +/- changes in storage.

What is the graph that shows river discharge and rainfall over time?

This means infiltration levels decrease and surface runoff increases. This leads to a short lag time and an increase in peak discharge. Hydrograph – a graph that shows river discharge and rainfall over time.

Why do drainage basins have a higher peak discharge?

1. Large drainage basins catch more precipitation so have a higher peak discharge compared to smaller basins. Smaller basins generally have shorter lag times because precipitation does not have as far to travel. The shape of the drainage basin also affects runoff and discharge.

What happens to the storm hydrograph after urbanisation?

The storm hydrograph after urbanisation. Rural areas with predominantly permeable rock increase infiltration and decreases surface runoff. This increases lag time. The peak discharge is also lower as it takes water longer to reach the river channel.

How does rainwater affect lag times?

Rainwater enters the river quicker, reducing lag times, as surface runoff is faster than baseflow or through flow. 5. if the rock type within the river basin is impermeable surface runoff will be higher, throughflow and infiltration will also be reduced meaning a reduction in lag time and an increase in peak discharge. 6.

How does the shape of a drainage basin affect runoff?

The shape of the drainage basin also affects runoff and discharge. Drainage basins that are more circular in shape lead to shorter lag times and a higher peak discharge than those that are long and thin because water has a shorter distance to travel to reach a river. 2.

Why do drainage basins have shorter lag times?

Drainage basins with steep sides tend to have shorter lag times than shallower basins. This is because water flows more quickly on the steep slopes down to the river. 3. Basins that have many streams (high drainage density) drain more quickly so have a shorter lag time.

Context for Use

This module has been used in courses in introductory geology, environmental geology, and surface water hydrology. However, we believe the module could be successful in many courses. Instructors should look over the material to decide how to best tailor these activities to their courses.

Description and Teaching Materials

This is probably too much material to cover in a three-hour lab period. You will need to select components of the modules based on your interests and the skill level of your students. For example, an introductory course may do a quick lab with just A and B, whereas an upper-level course might skip A and go straight to B and C.

Teaching Notes and Tips

See the Instructor's Manual (Microsoft Word 2007 (.docx) 106kB Jan25 17) and Instructor's PowerPoint (PowerPoint 2007 (.pptx) 15.8MB Jan25 17) for notes and tips for carrying out this exercise.

Assessment

In Activity A, students are introduced to variability in real stream data, using data from the USGS Hydrologic Benchmark Network.

References and Resources

There are probably more resources here than you will want to assign; choose readings that will complement the activities you will use.