GEOLOGY 102
Lecture 29 – Groundwater I
1) Groundwater
a) Where does groundwater reside?
i) ___________________ infiltrates into the subsurface and eventually enters
the groundwater system
ii) _______ of the water that infiltrates is returned to the air by
_________________________________
iii) other 50% enters the groundwater system where it remains for
______________ to ______________ to ______________ of yrs
iv) Water will eventually flow back to the __________________
v) Groundwater holds ________ of the planet’s ___________________ supply
2) Groundwater occurs in Pore Spaces
a) ________________ - any ____________ space within sediment or rock
b) ___________________ - total volume of ___________ space in a material (___)
c) 2 types of porosity:
i) ___________________ porosity – space that remains between solid grains
immediately after sediment ___________________ or rocks ________
(1) Function of: size and ___________________
(2) ___________________ with burial depth due to ______________ of
overlying sediment
(3) ___________________ in the transition from sediment to sedimentary
__________ - spaces fill with ___________________
(4) ___________________ rocks (igneous and metamorphic):
(a) Primary porosity is __________ - because minerals are interlocking
(b) _______________ and _____________ provide pores
(5) Highest in clastic sediments:
(a) Sands: ___________________
(b) Sandstone: 10-20%
(c) Limestone: ___________________
(d) Clay: 45-55%
ii) ___________________ porosity - ________
pore space in rocks created sometime
_________ the rock first formed
(1) Creation of secondary porosity:
(a) joints and ___________________
(b) dissolution and ______________ of
minerals (common in limestone)
3) Permeability
a) ___________________ - the ability of a material to
________ fluids to _________ through interconnected pores
i) Controlled by:
(1) ________________ of conduits
(2) ____________ of conduits
(3) route of conduits
ii) Permeable material – water flows ______________
iii) Impermeable material – water flows ______________ or not at all
b) Porosity and permeability are NOT THE SAME:
i) A material whose pores are _________________ can have _________
porosity and _________ permeability
(1) Mudstone: _________ porosity, _________ permeability
(2) Poorly sorted conglomerate: _________ porosity, _________ permeability
c) Aquifer - sediment or rock that _____________ water easily (______________)
i) _________ porosity and permeability
d) Aquitard - sediment or rock that ___________ transmit water easily
(____________________)
i) ______________ the motion of water
ii) _________ porosity and permeability
e) Aquiclude - does not transmit water ____________
f) Types of aquifers:
i) ___________________ aquifer –
aquifers that intersect the
_______________ of the Earth
(1) Water can percolate down
directly from the _____________
(2) Water can also ___________ to
the surface
ii) ___________________ aquifer – aquifers that are separated from the
surface by an ___________________
(1) Water is ________________ from the surface
4) The Water Table
a) 2 realms of groundwater:
i) Zone of ___________________ (unsaturated zone) – pores are filled with
_________________ and ___________________
ii) Zone of ___________________ (saturated zone) – pores are filled with
______________
b) __________________________ - the top of the zone of ___________________,
separates the 2 zones
c) _____________ of water table varies with location
i) Typically a subdued ____________ of surface ___________________
ii) Can be at the land surface (i.e. stream, marsh)
iii) In ____________ regions – typically within a few ______________ of the
ground surface
iv) In ____________ regions – may lie tens of meters to _______________
below the surface
d) Rainfalls effect:
i) Level ___________ during a ________ season or a
___________________
ii) Level ___________ during a ________ season or a
___________________
iii) If the water table ___________ below the floor of a river
or lake, the river or lake ___________________
(1) ___________________ stream – a nonpermanent stream, flows only
during storms when _________________ > ________________
e) Topography:
i) Shape of water table _____________ the shape of the overlying
___________________
(1) Groundwater moves very slowly and it cannot quickly assume a
__________________ surface
ii) Head (h) – the elevation of the surface of the water table above a
__________________ horizon
f)
5) Groundwater Flow
a) Groundwater does not stand still – it ______________
b) Zone of aeration - water percolates ________________ down due to the force of
_________________
c) Zone of saturation - water flows due to pull of ___________________ and due to
differences in ___________________
d) Pressure
i) Unconfined aquifer - ______________ is caused by the weight of overlying
_____________ (not overlying rock/sediment)
(1) ___________________ of pressure depends on the ___________ below
the water table
(2) If the water table is not ___________________ - pressure varies with
location
(a) Groundwater feels greater pressure under the __________, where the
water table is _____________
(3) Difference in pressure and force of _______________ causes
groundwater to follow a curved path
(4) Flows from regions where the water table is __________ (under a hill) to
regions where the water table is __________ (below a valley)
(a) ________________ differences drive water __________________
e) Recharge area – location where water __________ the ground
i) Flow direction has a ___________________ trajectory
ii) Locally, occur at the _______ of a ____________
f) Discharge area – location where water __________ the ground
i) Flow direction is ___________________ to the surface
ii) Locally, occur in the valley _______________
g) __________ of groundwater flow:
i) Typical rates – 0.01 – 1.4 m/day (_________________________)
ii) Slow because:
(1) Percolating through a ______________ network of _______________
(2) Follows a convolute path
(3) Travels a _______________ distance
(4) _______________ between conduit wall (mineral) and _______________
iii) Not always the same rate, controlled by:
(1) _____________________ of the material
(a) _______________ permeable > _______________ permeable
(2) slope of the water table
(a) _______________ the slope, the faster water moves
(b) Greater _______________ difference between _______________ and
_______________ areas
iv) Determined by “_______________” water with dye or _______________
element
v) Use ________________________ dating to determine the age of water
h) Hydraulic Gradient (HG) - _______________ of the water table
HGh/d
i) h = _______________ of the water table
ii) d = horizontal _______________ between 2 points
i) Discharge (Q) – the _______________ of water flowing
past a point in a _______________ time
Q=KIA
i) Q = _______________
ii) K = ______________________________ (controlled by _______________
and fluid’s _______________)
iii) I =HG= hydraulic _______________
iv) A = _____________________________ area through which water is passing
j) Equation is referred to as ______________________________
i) Groundwater flow is faster through very _______________ rocks than it is
through _______________ rocks
ii) And is faster where the water table has a _______________ slope than a
_______________ slope
6) Groundwater Chemistry
Groundwater contains ____________ derived from the ____________________ of
rock through which the groundwater passes.
Concentration of ions (________________) is controlled by __________________
and pressure.
-
warm water contains more dissolved __________ than cold water under great
pressures at depth
-
water under great _________________ at depth can hold more dissolved _____
than water at the earth’s surface
Presence of dissolved ions affects the value of water for human use
________________________ - forms when groundwater ________________
limestone or dolomite, then contains Ca+ and Mg+ ions
Carbonate minerals will _____________ to form the “scale” that ________ pipes
Also difficult to generate ___________ _______ when washing with hard water