Watershed Short Definitions
Table of Contents
Watershed Short Definitions
Dew Point:
When the existence amount of moisture so conducted that it changes in water, this temperature is called dew point. It is the temperature at which the air cannot hold all the moisture in it and dew begins to form.
Effective precipitation: –
The proportion of ppt, which actually reaches the ground, is called effective ppt.
Evaporation:
Total loss of water form a catchment in vapor form ie from a free water surface, from snow, soil surface and surface canopy
Gross ppt: –
The amount of ppt incident upon vegetate canopy.
Hydrograph:
A hydrograph is a chronological (in order of time) graphical representation of stream stage. Three segments can be distinguished in hydrograph.
- Rising limb
- Crest segment
- Recession limb
Interception: –
Interception is the process of catching precipitation by vegetation and then redistribution of it backed them atmosphere by vaporization or delivery to the ground:
Interception Loss: –
The portion of ppt that catches by vegetation and return to the atmosphere by vaporization processes is the interception loss.
Interception storage capacity: –
The amount of ppt which remains in the canopy after drip water and steam flow.
Net ppt: –
The amount of ppt which is delivered to the ground.
Pluviometer:
Measure the amount of rainfall
Pluviograph:
Measure the intensity of rainfall also called Embrometer.
Relative humidity:
Relative humidity is the ratio of the amount of water vapor in the air compared to the maximum amount of water vapor that the air could hold at that particular temperature
Saturation Deficit:
When there is further capability available in the air to hold water, it is called Saturation Deficit.
Snow Density:
Water equivalent (in inches) / Depth of snow (in inches)
Steam flow: –
The portion of ppt which the following interception reaches the ground by flowing down the stem is stem flow.
Sublimation:
The direct transition from solid to vapors or vapors to solid.
Through fall: –
The portion of ppt that reaches the ground directly through the openings in the vegetation canopy and as the drip from leaves and branch is termed as through fall.
Transpiration:
Loss of water through plants
Universal Soil Loss Equation:
Wischmier and Smith (1965) proposed an equation for estimating sheet and rill erosion in cultivated fields. This has been called as Universal Soil Loss Equation (USLE)
A = R * K * L * S * C * P
A = Soil loss tons/ acre
R = Rainfall erosivity index
K = Soil erodibility index
L = Slope length factor
S = Slope gradient factor
C = Crop mgt factor
P = Erosion control practice factor
Water balance/Hydrologic Equation:
“The relationship b/w ppt, storage, and release of water by stream flow and evaporation process is called Water Balance.”
The water yield: “The yield of a catchment is the residual of total ppt after vegetation and soil storage and evaporation losses have been shifted.”
Water Balance Equation:
The hydrologic equation refers only to amounts of stream flow. It says nothing as regards ‘time distribution’ of discharge this discharge regime, which is of particular interests economically.
Unfortunately, only stream flow and ppt can be determined with some degree of accuracy while the ‘loss factors’ in a catchment are not directly.
Q = P – (I + Tr + E + X) ± S
(Where; I = Interception; Tr = Transpiration; E = Evaporation; X = Deep percolation; S = Soil moisture contents before and after the precipitation/ Storage)
Water Stage:
It is the elevation of the water surface at a specified station above some arbitrary zero datum with mean sea level; often be set just below the point of zero flow.
Types of flow in Stream:
Effluent Stream: Also called Perennial Flow. When stream intersects the groundwater and groundwater basin is large enough to supply water around the year.
Influent Stream: When the bottom of the channel lies above the water table. The flow depends on the other runoff components.
Intermittent Flow: When water is supplied to stream by groundwater but not round the year.
Water yield:
The yield of a catchment is the residual of total ppt after vegetation and soil storage and evaporation losses have been shifted.
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