Catchment Water Budget Flashcards
What is the catchment of a river
The area of land that delivers all of its directly received precipitation to specified river
Where did the convent or catchment arise
Studies of Perrault (1674) and Marriott (1684) in the headwaters of the river seine (France)
Who created the idea of the hydrological cycle
Edmond Halley, 1687
What does the catchment water budget state
That the water lost by the catchment plus any change in subsurface water storage is equal to incoming precipitation
Equation of catchment water budget (water balance equation)
P = E + Q + ^S
Precipitation evapotranspirarion
River discharge
Change in storage
What are precipitation and evapotranspiration usually measured in
Mm/hr or mm/yr
What is discharge usually measured in
M3/s known as cumecs
How would we calculate the conversion of m3/s to mm/hr
To calculate the discharge per unit area of the catchment
M/s x 1000 x 3600 = Qmm/hr
Why can the change in subsurface be emitted from water balance equations
Over a period of a year or more it averages to zero
What is river catchment also known as
Drainage basins or watersheds
What are river catchments usually defined by
The surface topography, with the assumption that water entering the subsurface hydrological system eventually emerges within the same river catchment.
The ground water divide is assumed to be the same as the surface divide.
What three conditions leads to errors in assuming the ground water is the same as the surface divide.
If the surface of the impermeable rock ‘rock head’ has a different shape to the ground surface.
If there are dipping impermeable strata.
If there is a karstic subsurface hydrology were the subsurface flow is restricted to large cave systems.
Example of dipping impermeable strata
Wyresdale Catchment
Bowland Fells
Example of subsurface flow restricted to large cave systems
Doe Catchment
Ingleton
What is deep seepage
Where catchments ‘leek’ water, this subsurface exchange
What is gauge underflow (Hewlett 1982)
Where deep seepage is below the river outlet gauge
What are experimental catchments
Intensively studied catchments humans use to study their impact in water and related processes
How big are experimental catchments
1 to 10km2 in area
What experimental catchments are talked about in this module
Danum (Malaysia Borneo)
Plynlimon and Slapton (Uk)
Coweeta and Hubbard Brook (USA)
What is precipitation
Water reaching a catchment as rainfall, snow, hail, dew or occult forms
What is headwaters
Tributary stream close to the source of a large river
What is the hydrological cycle
The concept that evaporation gives water for precipitation which becomes subsurface water, then river water, then sea water, and evaporation once more
What is evapotranspiration
The water lost to the atmosphere by open water evaporation, water intercepted by the vegetation and directly re-evaporated plus biofuel transpiration from plants
What is subsurface water
All water below the ground surface, including soil water (i.e subsurface system close to the ground surface or water in the unsaturated zone) and groundwater (water below a regional water table)
What are the problems with water catchment
Different to rock head topography.
Dipping impermeable strata.
Karate systems with lots of caves.
Why do we study catchments on smaller scales
It’s difficult to do but scale
Examples of experimental catchments
Hubbard brook
Coweeta
Plynimon
Danum in Borneo
