Fetter Ch 1 – Water
1.1 - Water stats
 “elixir of life”
 relate to rise and fall of civilizations
 book discusses both surface and ground water
 person needs 3 liters of “potable” (drinkable) water per day
 single toilet flush may consume 23 ltrs (6 gal) – note there are new toilets that
use less than 1 gal per flush
 typical American uses 50-80 gal/day
Fetter makes point that, even with conservation measures, increasing population
will cause increasing world water usage to rise (Fig 1.1)
Note that Fetter cites declines, at least in US water usage, since 1980, which I
assume reflects heightened consciousness and conservation. However, many
intro science books continue to give impression that things are bad and ONLY
getting worse. You tell me…..
1.2 “Hydro” and “hydrogeo”
hydrology is study of water (hydrogen literally means “water-maker” for its role in
forming H2O…)
hydrogeology is study of water in its geologic context; typically implies
subsurface study of fluid flow through geological materials
Fetter points out that “movement and chemistry of GW are heavily dependent
upon geology”, both surface and subsurface
He also makes point that hydrogeo is both a descriptive and analytic science…I
assume this means you need to be able to describe things both qualitatively and
quantitatively, so this means some math is required – not a lot, but you’ll need to
be able to work some problems….
1.3 – Hydrologic cycle
Fig 1.3 shows apportionment of water on the planet…97% in the ocean.
Of the 3% that remains which is fresh, 2% of is locked up in glaciers and ice
caps. The bulk of the remaining 1% is GW. Some interesting stats on
atmosphere:
 Enough rain/snow falls on US every year to cover it to 30” deep
 22” of this 30” is evaporated back into atmosphere
 8” of the 30” runs off, infiltrates, finds its way to the ocean
Ch 1 p.2
We start the hydro cycle (Fig 1-4) arbitrarily at the ocean, where fresh H2O is
evap’d into atmosphere – no salts (Ca, Mg, Na, etc) are evap’d which is how you
can get fresh wtr from salt wtr.
Once precip starts to fall, terms start flyin’. Depression storage is a puddle; once
it overtops, it begins overland flow. It can also infiltrate and descend into GW
system.
Immed below surface is vadose zone, where soil pores contain both air and
water (things can be oxidized here). At base of vadose zone is the top of
saturated zone… this contact is what we call the “water table”. Water that occurs
below the water table is what we technically call ground water.
Groundwater tends to migrate toward discharge points such as lakes and
streams. GW contribution to a stream is known as baseflow; total flow is known
as runoff. Water in ponds, lakes, rivers, streams, is known as surface water.
1-4 Energy Transformations
Fetter makes interesting pt about hydro cycle being an “open system” – this
means that energy can enter into the system. He points out that energy of a
flowing river comes from the sun, in that solar energy is absorbed by water, is
evap’d into water vapor, is lifted to a higher elevation (gaining potential energy),
and then it falls back to earth and flows toward sea level.
Latent heats of evap and condensation are important concepts, not so much for
this course but for general knowledge of physical geog, weather, etc. Recall that
H2O can exist in gas, liquid, solid states, with the molecule having different
energy levels:
Gas
<----- >
High energy
+/- 600 cal/gm
Liquid
Intermediate
<------ >
Solid
Low energy
+/- 80 cal/gm
Calorie is a measure of heat energy, and is the amt of heat req’d to raise I gm of
water 1o C.
Latent heat of vaporization is energy absorbed by H2O molecule during evap to
vapor state, latent heat of condensation is energy given off from the molecule
during condensation out of vapor state….note that this is a lot of energy
available to the atmosphere to do work powering t-storms, etc, when water vapor
condenses in the atmosphere to form clouds, drop rain, etc.
Hv ( or Hc) = 597.3 - .564 T (cal / gram), where T is temp in oC
Ch 1 p.3
So roughly 600 calories for every gram of water involved are either given off or
absorbed in this process….this is a major amount of energy.
Lesser amount of energy is involved with latent heat of fusion, about 80 cal /gm.
This change of state is from solid to liquid or liquid to solid. Sublimation entails
direct change from solid to gas, or vice versa, and almost 700 cal/gm involved as
ice moves directly to vapor, or vapor moves to frost.
So why is all this important? “Vital to the heat balance of the Earth”.
For example, north and south of 38o latitude a net heat loss occurs over the year,
while between 38 N and 38 S there is a net gain. Since heat moves from high
energy to low energy (usually warm to cold), both air and ocean currents are set
up globally. Resulting weather and wind patterns create differing hydrologic
conditions throughout the world.
1.5 Hydrologic Equation
Hydrologic equation forms basis for quantitative eval of hydrologic cycle.
Reflection of law of mass conservation:
Inflow = Outflow +/-  storage
Or
 Inflow –  outflow =  storage
Lake example
 Variety of inflows: precip, streams, GW, overland flow
 Variety of outflows: evap, transpiration through plants, outlet streams, GW
seepage (note that GW can either enter or leave a lake, or both, depending
upon it’s position in regional flow system
 If inflow > outflow, lake volume increases, and amt “stored” there increases
(+  storage)
 If inflow < outflow, lake volume decreases, and amt “stored” there decreases
(-  storage)
Note: this equation is time-dependent – since things change through time, you
must make sure you measure inflows and outflows during same time period.
Ch 1 p.4
More terms:
 Drainage basin – all land sloping toward a particular discharge point
 Topographic divides – hills, ridges, mt chains - usually separate drainage
basins


Groundwater basin is subsurface equivalent of a surface drainage basin, and
is often coincident with the surface drainage basin
Groundwater divides are somewhat the subsurface equiv of topo divides
Look at Mono Lake, Calif as a case study for examining inflows, outflows, and
change in storage. Only outflow is evaporation. Lake starts at 53,500 acres in
size in 1941.
Examine lake level vs time (Fig 1-6) Periodic changes are natural from 1850 to
1941, then precipitous decline occurs due to diversions to LA Aqueduct for LA
drinking water. Drop from 6430 ft to 6370 ft, 60 feet vertically(!)
Wet conditions caused a temporary rise in lake level 1982-84, then return to
typical precip caused return to decline. Diversions halted in 1989. Lake continued
to fall due to very dry conditions. Fetter indicates that, if diversion resumed, the
lake would ultimately fall to about 6330 ft, and size half that of original. At this
size, outflow due to evap would balance with inflow from precip and GW, and
lake level would stabilize.
Ecological consequences: salinity rose from 5.4 % to 9.3 %, brine shrimp
population was disrupted, which disrupted industry and the food chain.
If lake level falls further, salinity will rise more, disrupt food chain even further,
including coyotes crossing over a land bridge and attacking seagulls (!).
Sections 1.6 to 1.9 devoted to descriptions of what hydrogeologists do, very
informative.
1.10 – Working the problems
solving problems is important part of course, and can be fun and rewarding. You
definitely will improve your quantitative literacy.
Fetter makes excellent point in his use of “dimensional analysis”. This technique
for quantitative problem-solving is on e of the most useful tricks I ever learned in
college. Here, you use the units of measurement as a guide for helping you set
up and solve problems. His conversion from miles to inches is excellent example.
Ch 1 p.5
You use the fact that units cancel each other out to “lead” you from the beginning
of your calculation to the end. Here, you’re left with inches at the end:
1.7 mi x 5280 ft x 12 in = 107,712 inches
1 mile
1 ft
the conversions you employ here don’t disrupt the “protocol” for answering the
problem….you are essentially multiplying your original 1.7 miles by “unity”.
Therefore, your conversion process does nothing to change what you started out
with….that is, you have not added any miles to the equation through your
conversion process.
Another factor to be comfortable with are the three basics, mass (M), time (T),
and length (L). Length can be squared (L2) or cubed (L3) to represent area and
volume.
These units can be used in many ways, for velocity, for concentration, density,
etc. Learn how to use them, to your advantage. Treat them as helping you, not
hindering you.