Soil Moisture and Groundwater Recharge

Question 1

The uppermost layer of the earth may contain a three-phase system called ________.

Answer 1

zone of aeration, unsaturated zone, vadose zone

Question 2

True or False. The solid phase of the vadose zone may not consist of soil, which is formed by in situ weathering or sediment, which has been transported from the place of weathering or unweathered bedrock.

Answer 2

False. May consist of soil.

Question 3

Larger units of smaller grains bounded by organic matter.

Answer 3

Aggregates or peds

Question 4

Determines the distribution of the size fractions of mineral grains present.

Answer 4

Soil texture

Question 5

Formula for gravimetric water content.

Answer 5

φg = 100 (Ww/ Ws)
φ g is the gravimetric water content (percentage)
Ww is the mass of the water in the soil (g or kg)
Ws is the mass of the solid particles (g or kg)

Question 6

The ratio of the volume of the voids to the volume of the solids.

Answer 6

Void ratio

Question 7

The volume of the contained water (Vw) divided by the total volume of the soil (V).

Answer 7

volumetric water content (φg)

Question 8

The volume of the contained water (Vw) divided by the volume of the voids (Vv).

Answer 8

saturation ratio (Rs)

Question 9

The dry mass of the soil particles (Ws) divided by the volume of the sample (V)

Answer 9

dry bulk density (pb)

Question 10

The mass of the mineral particles of the soil (Ws) divided by the volume of the soil particles (Vs)

Answer 10

Particle density (pm)

Question 11

Soil moisture can be measured indirectly by non-destructible means. One method involves burying small blocks, called _______ in which electrodes are embedded, and then passing an electrical current through the wire.

Answer 11

Resistance cells

Question 12

The subsurface layer in which groundwater seeps up from a water table by capillary action to fill pores. Pores at the base of the ____________ are filled with water due to tension saturation.

Answer 12

Capillary fringe

Question 13

The depression or the rise of a liquid in a small capillary passage tube having small cross-sectional area such as openings in the porous materials.

Answer 13

Capillarity

Question 14

Two forces of capillarity

Answer 14

cohesion and adhesion

Question 15

Mutual attraction between water molecules.

Answer 15

cohesion

Question 16

Molecular attraction between water molecules and different soil material.

Answer 16

adhesion

Question 17

True or False. Capillary rise is related to the diameter of the tube: The smaller the tube diameter the greater the rise of the water column.

Answer 17

True

Question 18

True or False. Capillarity is due to the adhesion of water to a surface and the cohesion of the adhered water to and among other water molecules.

Answer 18

True

Question 19

True or False. The capillary fringe can provide a means of indirect evaporation of groundwater, if the water table is close enough to the surface that the capillary fringe reaches the ground surface

Answer 19

False. Direct

Question 20

The measuring instrument used to determine water potential (soil moisture tension) in the vadose zone.

Answer 20

Tensiometer

Question 21

Water in the vadose zone is available for growing plants, found in the belt of soil water.

Answer 21

Soil water

Question 22

Soil moisture at a location varies with changes in the amount of _______ and ________.

Answer 22

Precipitation and evapotranspiration

Question 23

When soil moisture content of a layer reaches to the point at which the force of gravity acting on the water is equal to the surface tension, gravity drainage ceases.

Answer 23

Field capacity

Question 24

Happens when the remaining moisture is too tightly bound to the soil particles.

Answer 24

Wilting point

Question 25

True or False. Capillarity fringe rises as groundwater is being recharged

Answer 25

True