CHAPTER 6 Flashcards
It is the process and pathways through which excess water becomes streamflow’; excess water is that part of the total rainfall amount which runs off the land surface, and that which drains from the soil and is not consumed in evapotranspiration.
Runoff
It is the pathway in which rain falls directly into the stream chennel.
Channel Interception
It is the pathway in which excess water flows over the soil surface.
Surface Runoff or Overland Water Flow
It is a tabular or graphical representation of streamflow discharge against time.
Streamflow Hydrograph
Precipitation must satisfy the demands of evaporation, interception, infiltration, surface storage, surface detention, and channel detention before runoff can occur.
Runoff Process
Give the factors affecting runoff:
- Rainfall
- Watershed
- Control section
It is the duration, intensity and areal distribution.
Rainfall
It is the size, shape, orientation, topography, geology and surface culture.
Watershed
TRUE OR FALSE:
Intensity influences total runoff.
False
DURATION influences total runoff.
TRUE OR FALSE:
Intensity influences rate and volume of runoff.
True
TRUE OR FALSE:
An intense storm decreases infiltration rate because of its destructive action on soil structure at the surface.
True
TRUE OR FALSE:
Duration of rainfall influences rate and volume of runoff.
False
AREAL DISTRIBUTION of rainfall influences rate and volume of runoff.
TRUE OR FALSE:
Runoff is decreased for storms moving upstream.
True
TRUE OR FALSE:
Flat areas have low runoff.
True
TRUE OR FALSE:
Structures, soil materials and vegetation affect infiltration rate hence, runoff.
False
GEOLOGY, soil materials and vegetation affect infiltration rate hence, runoff.
TRUE OR FALSE:
Structures such as dams affect runoff rate.
True
Measurement of streamflow:
- Stage
- Rating curve
It is the height of water in a stream.
Stage
It is the graph of the stage and streamflow discharge.
Rating Curve
It is the section of stream for which a rating curve will be developed.
Control Section
Give the measurement of Stage:
- Staff Gauge
- Continuous water level recorder
It is a graduated staff used for the visual observation of water level.
Staff Gauge
Give the measurement of velocity:
- Float Method
- Current meter method
- Weirs
- Flumes
It is the time required for a floating object that is tossed into the stream to travel a specified distance on the surface of the water is observed.
Float Method
It is when the average velocity is multiplied by cross-sectional area of the stream to estimate streamflow discharge.
Float Method
It is an instrument in which a wheel is made to rotate about its axis by the force of current.
Current Meter Method
It is the speed of the rotation depends upon the velocity of water.
Current Meter Method
The general relationship between the numbers of revolutions and the velocity of streamflow is
V = a + bN
Current meter method
The ___________ is estimated by measuring the average velocity of each section with the current meter.
Streamflow Velocity
It is the barriers placed across the stream over which water flows; provides a simple and accurate means of measuring water.
Weirs
It is the height of water above the crest.
Head
It is the edge or surface over which the water flows.
Crest
It has a blade with a sharp upstream edge, so that the passing water touches only a thin edge and clear the rest of the crest.
Sharp-crested
It has a flat or broad surface over which the water flows.
Broad-crested
It is artificial open channels built to contain streamflows within designed cross-sectional areas and legnth.
Flumes
Types of flumes:
- Parshall Flume
- Trapezoidal Flume
