Lecture panel 2 Flashcards
What is hydrologic Science?
science of the waters of the Earth including:
- occurence/ origins
- distribution
- circulation
- physical and chemical properties
- reaction with the environment
- relationship to life
Where do the physical, chemical, and biological components of the hydrologic cycle occur?
within all components of the Earth system
-Atmosphere, oceans, solid earth, Ice sheets, rivers, lakes, biosphere
What must we know about to asses precipitation and evaporation?
climatology and meteorology
What must we know to assess infiltration and evaporation?
soil physics
What must we know to assess transpiration?
biological processes
What must we know to assess groundwater flow?
geology
What must we know to assess surface runoff?
geomorphology
What must we know to assess streamflow?
fluid mechanics
What are the two “states” of water in the hydrologic cycle?
reservoirs and fluxes
Principal storages in hydrologic cycle
- interception storage
- snowpack
- surface detention
- soil moisture
- groundwater
- streams and lakes
principal pathways of the hydrologic cycle
- precipitation
- throughfall and stemflow
- snowmelt
- infiltration
- percolation
- groundwater flow
- overland flow
- channel flow
- evapotranspiration
Major reservoirs in hydrologic cycle
oceans glaciers/snow groundwater lakes/rivers atmosphere
major fluxes in hydrologic cycle
evapotranspiration
runoff
precipitation
groundwater flow
Global annual average water balance values given in units relative to 100 for rate of precipitation on land:
precipitation on land - 100 evaporation from land - 61 moisture over land - 39 surface discharge - 38 groundwater discharge - 1 evaporation from ocean - 424 precipitation on ocean - 385
Where is Earth’s water stored?
97.22% Ocean
2.78% freshwater
for freshwater:
-77.78% surface (>99% in glaciers) (note: <1% of total water)
-11% GW, 11% deep GW
-0.18% soil moisture
properties of large reservoirs
low variability and greater persistence
residence time
(T) = average length of time a parcel of water spends in a particular reservoir. also called turnover time
T = Storage volume / flux
where flux is in units volume/time
Continuity/ Water balance equation
dS/dt = Inputs - Outputs
- change in storage over time
- inputs and outputs depend on the reservoir
What is a control volume?
“box model” - any substance that enters the control volume must leave at the same rate, or either accumulate or deplete supplies within
-steady state has no change in storage volume ie. fluxes are in balance
Types of control volumes in hydrology
- Basin
- sub-basin
- landscape units
- fields, forest stands
What scale is the concept of water balance useful at?
All scales:
- Macro-scale eg. continental watershed
- meso-scale eg. Grand River basin
- Micro-scale eg. leaf, field
What is the typical area for the water balance equation to be applied to?
catchment or watershed
-watershed is defined topographically
watershed definition
represents an area that will contribute all the water that passes through a given cross section of a stream (groundwater flow may be a separate source)
Water balance limitations
-all processes operate at different spatial and temporal scales that may not coincide with our measurements - adds imprecision in our assumptions
What is the general water year?
Oct 1 - Sept 30
-minimizes differences in storage (avoid spring surges, etc. i.e. calmest/steadiest time of year)
