Soil moisture and groundwater recharge Flashcards
The uppermost layer of the earth may contain a three-phase system of ____, ____, and _____ material
solid, liquid, and gaseous
the layer that contains the three-phase system is called the
zone of aeration, unsaturated zone or the vadose zone
the solid phase of vadose zone may consist of:
soil formed by in-situ weathering
sediments weathered and transported
unweathered bedrock
smaller grains may also be bounded by organic matter to form larger units called
aggregates or peds
the soil texture is determined by the:
distribution of the size fractions of mineral grains present
scientists break soils down into how many textural classes
12
scientists classify soils based on the percentages of ____, _____, and ____ paticles
clay, silt, and sand-sized particles
helps determine the drainage and fertility characteristics of a soil
soil texture
size ranges for sand, silt, and clay for soil scientists
clay - <0.002mm
silt - 0.002 - 0.05 mm
sand - 0.05 to 2 mm
is the mass of the soil water content divided by the mass of the solid particles (dry mass of the soil)
gravimetric water content
formula for gravimetric water content
gwc = Ww / Ws
mass of water in the soil / dry mass of the soil
the volume of the soil water divided by the volume of the soil
volumetric water content
formula for volumetric water content
vwc = Vw / V
volume of soil water divided by volume of the soil
formula for saturation ratio
Rs = Vw / Vv
volume of soil water divided by the volume of the voids of the soil
formula for dry bulk density
Pb = Ws / V
dry mass of the soil divided by the volume of the soil
formula for particle density
Pd = Ws / Vs
mass of the mineral particles divided by the volume of soil particles
soil moisture can be measured indirectly by
non-destructible means
one method of measuring soil moisture involves burying of ____ called _____, in which _____ are embedded and electric currents are passed through wires
small blocks
resistance cells
electrodes
small blocks that are buried in which electrodes are embedded to
resistance cells
is the depression or the rise of a liquid in a small capillary passage tube
capillarity
t or f: openings in the porous materials exhibit capillarity
T
this is the subsurface layer in which groundwater seeps up from a water table by capillary action to fill pores
capillary fringe
groundwater seeps up from a water table through
capillary action
pores at the base of the capillary fringe are filled with water because of
tension saturation
capillarity results from 2 force, what are these forces?
mutual attraction among water molecules (cohesion)
attraction of water molecules into different soil materials (adhesion)
t or f: because of capillarity, water level will rise in a small glass tube above the water level in a large container
T
the smaller the tube diameter, the _____ the rise of the water column
greater
the capillary fringe can provide a means for direct evaporation if
the water table is close enough to the ground surface
measuring instrument used to determine water potential (soil moisture tension) in the vadose zone
tensiometer
device that typically consist of glass or plastic tube with a porous ceramic cup filled with water
tensiometer
a tensiometer is a device used to determine _____ or _______ in the ______.
it consist of a ____ or _____ and a _______ filled with water
water potential
soil-moisture tension
vadose zone
glass or plastic tube
ceramic porous cup
water in the vadose zone available to growing of plants, found in the belt of soil water
soil water
soil water zone extend from
the land surface to the depth of roots of the plants
top of the capillary fringe may be below the
belt of soil water
soil moisture at a location varies with changes in the
amount of precipitation and evapotranspiration
also known as soil evapotranspiration
soil water evaporation
when the soil moisture content of a layer reaches to a point where the gravity attraction is equal to the surface tension, gravity drainage ceases.
Field capacity
field capacity happens when gravity equals the surface the tension, therefore _____
gravity drainage ceases
field capacity depends on the
specific retention
evaporation depth
unsaturated permeability characteristic curve of the soil
happens when the remaining moisture is too tightly bound to the soil particles
wilting point
field capacity is ______ proportional to grain size
inversely
soil texture with highest field capacity
clay
soil texture with lowest field capacity
sand
t or f: field capacity of a soil texture is directly proportional to its wilting point
T
10 soil textures arranged from lowest field capacity to highest
sand
fine sand
sandy loam
fine sandy loam
loam
silt loam
light clay loam
clay loam
heavy clay loam
clay
capillary fringe rises as groundwater is being ____
recharged
time of movement of infiltrating water is a function of
thickness of the unsaturated zone and the vertical unsaturated hydraulic conductivity
soil texture is important because it determines the
drainage and fertility characteristics of the soil
mixture of silt, David, and clay
loam
soil in usep obrero are mostly
clay and clay loam
soils are characterized by
sorting, size, and mineral grains present
weathered rock material containing organic compounds
soil
unconsolidated rock materials
regolith
what are peds
aggregate of soils
the ratio of the volume of the void to the volume of the solids
void ratio
common properties used to analyze/determine moisture content
porosity
void ratio
gravimetric water content
volumetric water content
saturation ration
dry bulk density
particle density
t or f: capillarity aids in evapotranspiration
T
a body of the tensiometer constructed of tough Butyrate plastic
irrometer body
irrometer body is constructed of
tough butyrate plastic
t or f: ceramic porous tip allows adhesion of water molecules
T
t or f: water table rise when groundwater is being recharged
T
annual precipitation in arid regions
<300 mm
annual precipitation in davao
1000-1,5000 mm
annual precipitation in surigao
> 2000 mm annually
high evapotranspiration causes water table to
lower
recharge and level of water table is dependent on the
thickness of unsaturated zone
precipitation
rate of discharge
hydraulic conductivity
topographic condition
geology
