Surface Hydrology: River Flow Flashcards
What is hydrology concerned with?
The occurrence & circulation of the waters of the earth in all their natural physical modes of movement. It deals with atmospheric, surface and
sub-surface phenomena.
Where do we extract water from?
- Lakes
- Soil Watert
- Rivers
- Ice
What volume of water is stored in oceans?
1370 10^6km^3
How can river flows be a hazard to society?
- Flood risk
- Drought risk
Whats an example of an irrigation project?
The Olmos irrigation project
What are the two key societal needs related to water resources?
- Direct supply (household, irrigation, industry).
- Indirect supplies (hydropower).
What is river discharge?
River discharge is the flux of water through a cross-section of a river at a specific point.
What is river discharge measured in?
It is typically measured in cubic meters per second (m³/s). It can also be normalized by catchment area, leading to dimensions of mm/day.
What is a hydrograph?
A hydrograph is a plot of river discharge over time, showing the variation of river flow rates.
What kind of problem can rivers be categorised in?
1-dimensional
What sources do rivers integrate the combined effect of?
- Spatial precipitation
- Evaporation
- Soil and ground water routing
What are measurements taken on for hydrographs?
Measured using gauging station
What are the common methods used to measure river discharge?
- Direct measurement of volume passing through a section (impractical in most cases).
- Velocity-area method: measuring the velocity across the river’s cross-section and multiplying by the area.
What is river hydrometry?
Science of measuring variables related to river flow
What is the formula for calculating river discharge using the velocity-area method?
Q = v × A, where v is the average velocity over the cross-section, and
A is the cross-sectional area
What are velocity meters?
Velocity meters, like the Valeport propeller meters measure river velocity
What is an ADCP?
Acoustic Doppler Current Profilers (ADCP) are used for larger rivers to measure water velocity by using sound waves
Why is it difficult to measure river flow using velocity alone, and what is a common alternative?
Measuring velocity is complex due to changes in river conditions. An alternative is to measure the river stage (water height) and convert this to discharge using a stage-discharge relationship
What can used to determine depth of water?
Pressure transducer
How can artificial controls like weirs and flumes help measure river discharge?
A weir or flume alters river flow, creating predictable flow conditions. This helps establish a reliable stage-discharge relationship, i.e., sub and super critical flows
What do we ideally want in the relationship between stage and discharge relationship?
Well -defined
What is the importance of separating stormflow from baseflow in hydrology?
Separating stormflow from baseflow helps understand the hydrological processes affecting a catchment. This is crucial for flood risk management, as stormflow contributes to peaks in river discharge.
What factors effect stage-discharge relationship?
- Vegetation cycles
- Ice cover
- Rising and falling limb of the hydrograph
What formula can be calculated from the use of weirs and flumes for discharge?
Q = KbH^(1.5)
What re some flow indicators?
- Maximum flow
- MInimum flow
- Mean flow
- 10th percentile
- 90th percentile
What can flow measurements be described as?
Instantaneous
What isa river flow measurement?
Momentary recording of the state of the river
How do you calculate storm flow?
Total flow- base flow
What can lead to peak discharge?
- heavy rainfall
- snow melt
- rainfall on frozen or saturated
What are some temp dependant regimes?
- Glacial
- Mountain snow melt
- Plain snow melt
Flow records across what time span are required?
20 - 30 year
What is the start of storm flow called?
- Inflexion point
How to find of end of storm flow?
precipitation_end + (NxTL)
What is the lag time?
Peak storm flow - peak precipitation
