Hydrology

Question 1

evapotranspiration

Answer 1

Evapotranspiration (ET) is the combined processes by which water moves from the earth’s surface into the atmosphere

Question 2

transpiration

Answer 2

Transpiration is the process of water movement through a plant and its evaporation from aerial parts, such as leaves, stems and flowers

Question 3

percolation

Answer 3

the downward movement of water through soil layers due to gravity and capillary forces

Question 4

interflow (subsurface runoff)

Answer 4

relatively rapid flow toward the stream channel that occurs below the surface. It occurs more rapidly than baseflow, but typically more slowly than surface runoff.

Question 5

interception

Answer 5

relatively rapid flow toward the stream channel that occurs below the surface. It occurs more rapidly than baseflow, but typically more slowly than surface runoff through evaporation

Question 6

ground water recharge

Answer 6

a hydrologic process, where water moves downward from surface water to groundwater. Recharge is the primary method through which water enters an aquifer.

Question 7

base flow

Answer 7

the portion of the streamflow that is sustained between precipitation events, fed to streams by delayed pathways

Question 8

vadose zone (unsaturated zone)

Answer 8

zone that extends from the top of the ground surface to the water table.
-includes the soil, intermediate and capillary zones

Question 9

phreatic zone

Answer 9

(zone of saturation) The soil or rock zone below the level of the water-table, where all voids are saturated.

Question 10

intermediate zone

Answer 10

zone that separates the saturated phreatic zone from soil water

lies above the capillary fringe and consists of water in
the form of thin films adhering to the pore lining. This water is free to drain
downward under the forces of gravity.

Question 11

interstitial water

Answer 11

subterranean water in the pores of rocks, soils, and bottom sediments of oceans, seas, and lakes

Question 12

What is Vt?

Answer 12

the total volume of water in both solids (Vs) and voids (Vv). Only voids are able to hold both air and water.

Question 13

degree of saturation

Answer 13

ratio of the water volume to the void volume expressed as a percentage (Vs/Vv X 100)

Question 14

degree of saturation less than 100%

Answer 14

indicates that air occupies some of the voids

Question 15

moisture content

Answer 15

the volume of water divided by the total volume (Vw/VT X100) expressed as a percent

Question 16

capillary water zone

Answer 16

t the contact between the lower part of a dry porous material and a saturated
material, the water rises to a certain height above the top of the saturated material. The driving force for this is surface tension which can be compared to a stretched membrane

Question 17

surface tension

Answer 17

a force acting parallel to the surface of
the water in all directions because of an unbalanced molecular attraction of the
water at the boundary

Question 18

water table

Answer 18

the underground water surface at
which the pressure is exactly equal to atmospheric

water above this table is at a
pressure below atmospheric while water below this table is at a pressure
greater than atmospheric

Question 19

evaporation

Answer 19

the process of liquid turning into gas without boiling, such as water becoming water vapor and is powered by heat
-can take place in both soil and free water surfaces
plants=evapotranspiration
-evapotranspiration= both plants and soil (combination of the two)

Question 20

potential evapotranspiration

Answer 20

the amount of water that
would evaporate or transpire from a surface if water was available to that surface
in unlimited supply
-is a temperature dependent quantity, and is a measure of the moisture
demand for a region

• The
  vegetation (or lack thereof) in a region is thus a reflection of the precipitation-potential evapotranspiration ratio

Question 21

rules that govern the hydrologic cycle

Answer 21

-when precipitation is equal to potential evapotranspiration, the surplus = 0
-when the rate of precipitation exceeds the rate of infiltration, there will be some water available for overland runoff
-when the temperature drops sufficiently so that precipitation exceeds potential evapotranspiration, a water surplus is realized
-soil zone serves as a buffer- taking in moisture during surplus periods and releasing moisture during deficit periods

Question 22

maximum permissible infiltration ___ with increasing time

Answer 22

decreases

Question 23

infiltration capacity

Answer 23

the maximum rate by which water on the ground surface enters the soil

Question 24

field capacity

Answer 24

used to denote
an upper limit of moisture content in soils. This is when the soil is holding all
the water it can under the pull of gravity
-both interflow and ground water recharge can commence when the moisture content exceeds this capacity.
-dependent on the nature of the soil zone. Thinner soils with impervious rocks = interflow may be dominant. Thicker pervious soils = downward migration may dominate

Question 25

base flow

Answer 25

component of streams represents the withdrawal of ground water from storage and is termed ground water recession

Question 26

hydrograph

Answer 26

consists of overland flow, interflow, and base flow

Question 27

effluent or gaining streams

Answer 27

Streams that receive water from the ground water reservoir by the base flow component

Question 28

influent or losing streams

Answer 28

Streams
that lose water to the ground water reservoir. This occurs when the ground water table
is well below the base of the stream.