1. Water: Process, Supply, and Use
There is plenty of fresh water:
Atmosphere %
Rivers and streams %
Lakes %
Groundwater %
total 4 million km3
...but rarely where we want it in the right form

2. Water: Process, Supply, and Use
Global per capita water use is 2 m3/day
US is 5 m3/day
By 2000 will use 6000 km3/yr = 5% of total in lakes and rivers (including a huge amount in uninhabited areas, so locally much higher %)
Of course this is renewable, but also pollutable
US Water Resources Council est. by 2020 American water use may exceed surface resources by 13%
Most of Americans use water that has been used at least once before

3. Water: Process, Supply, and Use
Surface water covered in largely in rivers section
Surface water supply is controlled largely by precipitation

4. Water: Process, Supply, and Use
Areas with < 65 cm/yr have inadequate surface water supplies
The West (particularly the Southwest) are headed for trouble
How can we make up the difference?

5. Water: Process, Supply, and Use
Groundwater
Fig. 10-6
Water table = top surface of saturated zone
Capillary fringe: water drawn up by capillary action
Groundwater usually flows due to slope of water table

6. Water: Process, Supply, and Use
Aquifer: high porosity and permeability (+ water)
Clastic sediments
Fractured igneous or metamorphic
Basalts and upper brecciated zone, joints, soil/interbeds
Dissolved limestone
Impermeable layers are called aquitards (or aquicludes) clay, igneous…

7. Water: Process, Supply, and Use
Confined vs. unconfined aquifers
“potentiometric surface”
Artesian wells: under pressure beneath an aquiclude- water rises up the well pipe
Flowing artesian wells actually rise above the ground surface
Water table wells are the common type

8. Water: Process, Supply, and Use
The same principal works in terms of municipal water supply

9. Water: Process, Supply, and Use
Springs occur when the contact between an upper aquifer and a lower aquitard intersects the ground surface

10. Water: Process, Supply, and Use
Where to drill and how deep are difficult questions and require good subsurface data
Cost of drilling a well averages $15/foot
10 ft. may be fine in a floodplain
Generally deeper on slopes of hills
A 1000’ well costs $15,000

11. Water: Process, Supply, and Use
Pumping usually faster than recharge due to limited permeability of the aquifer
Cone of depression
Effect on neighbors
Some recovery when cease pumping
Compaction when lose water support can cause permanent decrease in porosity and permeability

12. Water: Process, Supply, and Use
Perched aquifer: held above the normal water table by an aquiclude

13. Water: Process, Supply, and Use
Groundwater flows into an effluent stream in wet climates
This is a result of discharge from the aquifer
Groundwater flows out from an influent stream in dry climates
This results in recharge to the aquifer
Recharge areas are often far from the discharge zone or point

14. Water: Process, Supply, and Use
Water Supply
Water supply depends on climate, geology, stream flow, subsurface flow...
Budget = annual runoff + groundwater
Cannot contain and use all runoff
Cannot extract and distribute all of groundwater
Much groundwater is available where surface water is also
Cannot contain all runoff and use it because it is seasonal & has a limited reservoir capacity
There may be lots of groundwater, but cannot extract it all and not distributed as we might like
Much of groundwater is available where surface water is also

15. Water: Process, Supply, and Use
Water Supply
In much of the American West there is often little surface or groundwater
In places where there is groundwater and little surface water, there is a tendency to overdraw, or “mine” the aquifers (non-renewable)

16. Groundwater overdraft for conterminous US in 1975
(Florida in East due to saltwater encroachment)

17. The Ogallala (or High Plains) Aquifer
> 170,000 mi2 and holds > 7 x 1016 gallons of water
Charged in glacial times (over 12,000 yrs ago)
Current recharge from rainfall (< 16-20”/yr)
Main source of water in several arid states
The availability of water from the Ogallala led to considerable agricultural development

18. What do we do when the Ogallala aquifer runs dry?
One study said that by 2015 the Ogallala will be so reduced and pumping will be so expensive due lowering of the water table that crop yields will be down by 80% and 300,000 people will have to migrate away
Where can they go?

19. Water: Process, Supply, and Use
Movement of water to people
1. Withdrawal: quantity diverted or taken from surface or groundwater (A)
2. Delivery to point of use (B)
3. Release to pt. of return (C)
4. Conveyance loss: lost in transit (A ® B)
5. Consumptive use: portion evaporated, leaked, transpired, or absorbed by crops, etc.
6. Return flow: amount returned to surface or groundwater and available for future use

20. Water: Process, Supply, and Use
Movement of water to people
California:
Source of water is runoff in north
S. California indigenous water could support ~250,000 people
Many cities experiencing shortages, groundwater pollution, salinization (from agriculture and encroaching seawater), etc.

21. Part of Southern California’s answer to its water problem is an alternative to groundwater withdrawal: aqueducts and canals

22. Water: Process, Supply, and Use
Water Quality
Dissolved material in ppm (or ppb)
TDS = total dissolved solids (should be < ppm)
“Hard” water: > CaCO3 – MgCO3
Causes “scale” in boilers and hot-water pipes
Prevents soap from lathering & rinsing
Water softeners exchange Na+ for Ca++ and Mg++

23. Water: Process, Supply, and Use
Water conservation is fairly effective since mid 1970’s
Drip irrigation
Industrial conservation
Home conservation
Running water or leaks (including mains), toilets, showers/baths, lawn watering, letting water run while washing dishes...

24. Water: Process, Supply, and Use
Movement of water to people
Water management
Geologic and climatic factors as well as political and economic
Flood prevention in times of high flow and conservation/distribution when low
Conserve groundwater when surface water is available: don’t mine it
Desalination may provide fresh water

25. Water: Process, Supply, and Use
The Colorado: a managed river
Mostly rural water is collected and distributed by dams, reservoirs, aqueducts, canals, and pipes to agriculture and millions of urban residents

26. Water: Process, Supply, and Use
The Colorado: a managed river
Flow only 3% of the Mississippi, but lifeline of most of the Southwest
Elaborate system of distribution, allocation, rights, legal squabbles, etc. between 7 states + Mexico
Glen Canyon dam was built at the political boundary between the Upper and Lower Colorado districts
Divided water rights between U & L basins
Highly variable annual flows
Evaporation and infiltration from reservoirs
Salinity and pollution

27. Water: Process, Supply, and Use
The Colorado: a managed river
Allocations made following an unusually wet decade
® over-allocation when flows returned to normal levels
Central Arizona Project just finished (S. California has used 0.6 Maf of Arizona’s allocation)
California must relinquish it when CAP finished (it is - did they?)

28. Dams and Reservoirs
Dams are multifunctional, but generally designed for
Flood control
Hydroelectric
Ancillary uses:
Recreation
Irrigation and municipal water supply
Navigation
Negative effects:
Flood large areas: affect human/animal habitat
Interrupt fish migration
Interrupt sediment flow

29. Water: Process, Supply, and Use
Water and Ecosystems
Natural ecosystems reflect a balance between climate, nutrients, soils, biota, hydrology...
Humans are now degrading most ecosystems on a regional and global basis
The most damaging effects are associated with degraded surface water conditions
The effects can be far-reaching: even to the oceans (Aswan) and atmosphere (Amazon)