Lesson 2: Elements of Hydrologic Cycle Flashcards
the process by which water changes from a liquid to a gas or vapor state
evaporation
the primary pathway that water moves from a liquid state back into the water cycle as atmospheric water vapor.
evaporation
the number of grams of water per cubic meter
absolute humidity
maximum amount of moisture the air can hold in given temperature
saturation humidity
max amount of water that can be stored in 1 cubic meter of air in a given temperature
saturation humidity
how does saturation humidity and air temperature relate to each other?
they’re directly proportional to each other
percent ratio of absolute humidity to the saturation humidity for the temperature of the air mass
relative humidity
what happens to evaporation as relative humidity approaches 100%
evaporation stops and condensation starts
What happens when the air mass can no longer hold all of its humidity?
condensation starts, (aka 100% relative humidity)
what happens to relative humidity if the absolute humidity remains constant
the relative humidity will rise
what happens when relative humidity reaches 100% and there is further cooling
condensation starts
name of temperature at which condensation will begin
dew point
Growing plants are continuously pumping water from the ground into the atmosphere through the process of ?
transpiration
how much water is being transpired by plants?
50-60 gals/hr
what enables the travel of water from soil roots to leaves?
osmotic pressure
opening surface of leaves where air may pass through. they are responsible for gas exchange and help with photosynthesis and hydration
Stomata
what part of the plant is the stomata located
for land plants, at the underside of leaves, for water plants at the upper surface of leaves
Amount of transpiration is a function of what two factors?
density and size of drainage basin
what season is transpiration especially important
plants’ growing season
WHEN does transpiration happen?
95% takes place during daylight, during photosynthesis
what limits transpiration?
the availability of soil water
soil-water content becomes low that surface tension of soil-water interface exceeds the osmotic pressure of roots and subsequently causes water to no longer enter the roots
wilting point
plants with taproot system extending to the water table
phreatophytes
describe the leaves and stalks of typical phreatophytes
-thick leaves
-spiky stalks to deter grazing animals
desert plants
xerophytes
aquatic plants
hydrophytes
example of xerophytes
succulents (have fleshy leaves): aleo, agave, peperomia, haworthia, kalanchoe, bryophyllum
example of hydrophytes
lily, lotus, lemna, wolffia, hydrilla, eichhornia
accounts for the movement of water to the air from sources such as the soil, canopy interception, and water bodies
evapotranspiration
describe the potential evapotranspiration vs actual evapotranspiration, also describe precipitation in an area with:
1. coarse soil, limited soil moisture storage, warm dry summers and cool moist winters
2. fine soils with ample soil moisture storage, warm summers, cool winters and little seasonal change in precipitation
- very much less actual evapotranspiration compared to potential, little precipitation
- actual evapotranspiration is close to (almost as much as) the potential, a lot of precipitation
*clay can hold more water thus evaporate more
how to measure evapotranspiration?
Evapotranspiration can be measured directly using a lysimeter
a large container holding soil and plants
lysimeter
how does a lysimeter work?
> It is set outdoors; initial soil-water content is determined.
precipitation and any irrigation water added are measured
changes in soil-moisture storage reveal how much of the added water is lost to evapotranspiration
at least 3 parts of a lysimeter
tensiometer, suction, electrodes
what exactly can a lysimeter measure?
soil water content, temperature, electrical conductivity of soil
formula for the evapotranspiration of a period
Er = Si + PR + IR - Sf - DE
Si -volume of initial soil water
PR -precipitation into the lysimeter
IR -the irrigation water added to the lysimeter
Sf -volume of final soil water
DE -excess moisture drained from the soil
what happens When an air mass with a relative humidity lower than 100% is cooled without losing moisture
the relative humidity will approach 100% as the air approaches the dew-point temperature.
what may start to occur when the air mass is saturated?
condensation may start to occur
what does condensation need to form?
a surface or nucleus
specific examples of nucleus for condensation to form
clay minerals, salts, combustion products (aerosols -suspended air molecules)
what happens when there is no nucleus for condensation?
air mass may become supersaturated without the formation of raindrops or ice crystals
what happens when there is a nucleus for condensation to form?
- the air mass then starts to grow by attraction (diffusion) of water vapor and additional condensation
- cloud elements collude and coalesce, then
- raindrops begin to form
4 needed parameters needed to initiate precipitation
- Humid air mass must be cooled to the dew-point temperature.
- Condensation of freezing nuclei must be present.
- Droplets must coalesce to form raindrops.
- Raindrops must be of sufficient size when they leave the clouds to ensure that they will not totally evaporate before they reach the ground
Air masses are cooled by a process called?
adiabatic expansion
occurs when the air mass rises in the atmosphere and expands owing to the decreasing pressure
adiabatic expansion
When the air mass reaches the dew point temperature, further lifting and cooling will cause condensation. what is released?
the latent heat of vaporization is released
unit for rain gauge
mm or cm
how to measure precipitation and snow?
Any open container (rain gauge) can be used to catch and measure rainfall
-opening size has little effect (except for those less than 3 cm in diameter)
-affected by high winds
-location/placement is critical: should be close to the ground as possible, avoid winds, in open area, away from trees
-if steep slopes, opening should be parallel to slope
in urban areas, where is the rain gauge placed?
at the roof of buildings
standard rain gauge diameters for the US, Canada and PH?
US -20.3cm or 2/3 of a ruler
Canada -9cm
Ph(?) -8 inches
technology that can be used to remotely measure the intensity of precipitation on the area
radar
how long does it take to determine the effective depth of precipitation
may be determined for time periods ranging from the duration of part of a single storm to a year
what data are being measured when determining the depth of precipitation?
The data are generally measurements of precipitation and/or equivalent snowfall at a number of points throughout the drainage basin.
what could be the cause of data missing at one or more stations when measuring the effective depth of precipitation?
equipment malfunction or operator absence. this would create a problem
what should be done if data missing at one or more stations when measuring effective depth of precipitation
To solve the problem, three close precipitation stations with full records that are evenly spaced around the station with a missing record are used.
use the Pz formula
If the rain gauge network is of uniform density, how to tell the depth of precipitation?
arithmetic average of the point-rainfall data for each station
for US standards, precipitation amounts are in what units? how about station locations? (how about for PH?)
precipitation -cm
location -in decimal places
in PH, stations are just named after minicipalities
If the rain gauge network is not of uniform density, how to tell the depth of precipitation?
some adjustment is necessary
what’s a more accurate method to measure depth of precipitation
to draw a precipitation contour map with lines of equal rainfall (isohyetal lines)
show contours of equal rainfall depth
isohyets (isohyetal lines)
what are the contours in isohyets based on?
simple linear interpolation
Satellite used by DOST and PAG-ASA to monitor typhoon trajectory
DOST HIMAWARI-8 Satellite
shows the discharge of a river at a single location as a function of time
stream hydrograph
method to adjust non-uniform gauge distribution uses a weighing factor (based on the area within the
drainage basin) for each rain gauge.
Thiessen method
how to construct Thiessen polygons
✓ The stations are connected with lines.
✓ The perpendicular bisector of each line is found.
✓ The bisectors are extended to form the polygons around each station
effect when one side of a mountain has high precipitation but the other side is arid, thus if we use the Thiessen method, it would yield wonky results
orographic effect
aka gaining stream
effluent stream
what type of stream is typical in humid regions and why?
effluent streams, because groundwater is able to recharge them
aka losing stream
influent stream
type of stream typical in arid regions, and why
influent streams because they recharge groundwater
what happens to a stream during flood stage if it is gaining during low-flow periods
can become temporarily a losing stream during flood stage
what happens to the rate of baseflow if the rate of infiltration increases (during gentle rain)?
the baseflow increases, more is being fed to the stream, thus the stream is now deeper and has a greater discharge
