Exam 1 Flashcards
Modern Hydrology
the dist of water on Earth’s surface and the movement of water (under/over surface and throughout atmosphere)
Hydrologist
primary focus is fresh water
Water Distribution %s
Oceans: 96.8%
Freshwater: 3.2% (ice=75%; GW=25%) lakes: 0.3; Biosphere: 0.24; soil: 0.06; clouds: 0.03; rivers: 0.003
Amount of freshwater available for use:
0.3%
Water demand growth per year
60 billion cubic m/year
water stressed defiition
any country with less than 1700 cubic m/person
% people water stressed by 2030
47%
% population at risk of water shortages
80%
Global use of water
world avg (ag: 70%; industry: 22%; Domestic: 8%)
Low/middle income countries (ag: 82%; Industrial: 10%; domestic: 8%)
High income countries (industrial: 59%; ag: 30%; domestic 11%)
Water Budget Equation
in flow - outflow = chg storage
P + E + Q + chg S = 0
Precipitation
the release of water from the atmosphere to the surface of the Earth
(expressed as vertical depth)
happens when atmosphere is saturated, small particles present (dust)
water/ice particles large enough to reach earth against updrafts
Boyle’s Law:
P = 1/V
If temp cools:
there is less ability of air to hold moisture (condensation: dew/frost)
Convective precipitation definition
uplift caused by heating of the Earth’s surface
Orographic precipitation definition
air mass is forced to rise over an obstruction (ex: mountain range)
Frontal/ cyclonic precipitation definition
a low pressure weather system where air is constantly being forced upwards
Cloud seeding definition
purposefully putting particles of some sort in the air to entice precipitation to occur
Collision coalescence definition
droplets grow as they collide with other smaller droplets as they fall -pressure will often lift them again until they have enough mass (usually in warm clouds abt 5F)
Bergeron Process definition
a process of ice crystal growths in clouds containing a mixture of supercooled water (abt -40F) and ice when ambient vapor pressure falls between the saturation vapor pressure over water and the lower saturation vapor pressure of ice.
Since ice has less vapor pressure than the supercooled water and water vapor, the water will connect to the ice particles, increasing their size. This often results in precipitation.
(large particles grow at expense of small)
-most common at mid - high latitudes
Dewfall definition
dew forms as temps drop and objects cool down - if cool enough, will also cool air, making it less able to hold the vapor, so the water vapor condenses into dew
Static influences on precipitation distribution
geography, altitude, aspect, and slope
rain shadow definition
when the geographical differences in rainfall in two adjacent regions are very visible (ex: forested mountains vs desert valley)
Rainfall measurement errors
instrumentation and sampling errors
Wetting loss definition
water that stays on the surface of the tunnel and is lost to evaporation
deciding how many rain gauges are needed
the number of gauges will increase with the size of the watershed
Arithmetic mean
taking average of all gauge estimates
Theissen’s polygons
weighed average of what areas are most impacted by the rain (split into ranges)
ex: 30% of watershed had 2 in rain
Hypsometric Method
similar elevations get averaged together (topography)
Isohytel
find similar places and group them
Evaporation definition
the transfer of liquid into a gaseous state
Evapotranspiration definition
evap from soils, water, plant interception, and transpiration
Transpiration definition
when the plant roots absorb water, it goes to leaves which then increases to solute conc. This creates an “osmotic pressure gradient” so the stomata open to relieve pressure. The water is evaporated out of the stomata.
(70% of precip)
Evapotranspiration formula
ET = P - Q - chg S - chg l (deep storage)
Net Radiation
measure of the amount of energy received at the surface (Q)
Vapor flow
a water molecule moves from a higher conc to lower conc.
Vapor pressure at evap surface than receiving atmosphere: this pressure is largely controlled by temp
Factors affecting interception
- intensity of precipitation
- wind velocity
- Evap demand after rainfall
- leaf type
- leaf and branch SA
Interception definition
when water is stopped from going to ground by trees and other obstructions
Throughfall definition
the water that falls in between obstructions like trees to the ground
Stem flow definition
water that runs down the trunks and stems of trees and plants (< 2%)
Net Precipitation
amount of precipitation available for surface ground water
Gross precipitation
total precipitation minus that lost by evaporation
what trees have highest interception
conifers (more SA)
Of grasslands, bare soils, and forests: which have highest evaporation rates?
Forests at 20-40% interception
grasslands intercept 10-20%
(but it still depends on exact type of ecosystem ex: mixed hardwood vs conifers)
Direct micro-meteorological measurement devices
Anemometers
Eddy
Aerodynamic
Bowen ratio
Indirect micro-meteorological measurement devices
Evaporation pans
Lysimeters
Eddy
measures water vapor increases on the surface with vertical wind speed and temperature
Requires an anemometer
Aerodynamic Profile Method
calculates the amount of energy available for evaporation to determine actual evap rate
Bowen Ratio
similar to the Aerodynamic method but does not assume variations
Evaporation Pans
measuring amount of evaporation (easy and cheap method)
Lysimeter
complex versions of evaporation pans (giant buckets on scales)
-can grow grass to imitate surface evaporation
problems with evaporation pans
- open water measurements- sig higher than normaql evap
- edge effect (will warm up faster)
Role of Forest litter in interception
- can store part or all of throughfall
- storage capacity can be great (depending on litter type)
- Moisture content is generally high
What does Q stand for?
Streamflow
Relationship between evaporation and pressure
Inverse
Infiltration capacity
maximum rate that water can enter the soil
Infiltration rate
instantaneous rate at which water enters the soil
Soil water
amount of water contained within the soil
infiltration
process of water entering the surface of the soil
percolation
process of water movement through the soil
Is pore size, capillary action, or gravity NOT responsible for infiltration of water
pore size
the gravitimetric method is most similar to what soil expression
Oven-dry water content
T or F: highly porous soil reaches the wilting point fastest given a relatively low depth of water per depth of soil
True
T or F: Field capacity is related high soil water tension
True
Dangers of limited water access
Diarrhea, typhoid, cholera, malaria
3 Types of Uplift
Convective, Orographic, and frontal/cyclonic
Temp for collison coalescence
Around 5 degrees F
Temp for Bergeron Process
Around -40 degrees F
