Exam 1 Flashcards by abbey welch

Modern Hydrology

the dist of water on Earth’s surface and the movement of water (under/over surface and throughout atmosphere)

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Hydrologist

primary focus is fresh water

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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

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Amount of freshwater available for use:

0.3%

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Water demand growth per year

60 billion cubic m/year

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water stressed defiition

any country with less than 1700 cubic m/person

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% people water stressed by 2030

47%

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% population at risk of water shortages

80%

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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%)

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Water Budget Equation

in flow - outflow = chg storage

P + E + Q + chg S = 0

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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

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Boyle’s Law:

P = 1/V

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If temp cools:

there is less ability of air to hold moisture (condensation: dew/frost)

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Convective precipitation definition

uplift caused by heating of the Earth’s surface

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Orographic precipitation definition

air mass is forced to rise over an obstruction (ex: mountain range)

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Frontal/ cyclonic precipitation definition

a low pressure weather system where air is constantly being forced upwards

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Cloud seeding definition

purposefully putting particles of some sort in the air to entice precipitation to occur

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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)

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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

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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

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Static influences on precipitation distribution

geography, altitude, aspect, and slope

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rain shadow definition

when the geographical differences in rainfall in two adjacent regions are very visible (ex: forested mountains vs desert valley)

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Rainfall measurement errors

instrumentation and sampling errors

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Wetting loss definition

water that stays on the surface of the tunnel and is lost to evaporation

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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