FRESH WATER BREAKDOWN
About 75 percent of the fresh water is more or less permanently stored in the polar ice caps and glaciers. In North America, about one-third of one percent of the total fresh water is in lakes and rivers., and about 20 percent of this is in the Great Lakes! About one fourth of the earth’s fresh water supply is beneath the surface of the land. Most of this is bound up physically or chemically in soil and rock formations, leaving but a fraction of this "groundwater" for use. I was once shocked many years ago in college, when the instructor said that we get to use about "one cup out of every million gallons of water" on the planet!

WATER QUANTITY ISSUES:
a) Droughts and other unequal precipitation cycles over the years, make the storage of water a major factor in the conduct of our business.
b) In the continental United States the average annual precipitation is about 30 inches.
c) Of this amount, about 21 inches is lost to the atmosphere by evaporation and transpiration.
d) The remaining 9 inches becomes runoff into rivers and lakes.
e) Precipitation and runoff vary greatly with local geography and the season of the year. Annual precipitation varies from more than 100 inches in parts of the northwest to only 2 or 3 inches in parts of the southwest.
f) Generally speaking, there are greater variations in runoff rates from smaller watersheds. A critical water supply situation occurs when there are three or four abnormally dry years in succession..
g) The total amount of water stored in our reservoirs, lakes, and in the aquifers is important as it enables us to utilize water continuously even though the replenishment or replacement of our stored water does not take place while it is being "consumed". Obviously, we cannot use water at a rate which exceeds the rate of replacement. This is "mining."

GROUND WATER AND WELLS: Wells and springs are the principal means of obtaining groundwater supplies. Groundwater’s are characterized by:
a) lower color levels
b) freedom from microbial contamination,
c) higher hardness than surface waters,
d) higher dissolved solids and gases values,
e) and less variability in water quality parameters.

"Safe yield" for groundwater sources is the quantity and/or withdrawal rate of water that does not
a) cause land subsidence,
b) drastic lowering of the water table, or
c) saltwater intrusion.
Hardness is the result of water percolating through mineral deposits containing such elements as calcium and magnesium. Groundwater usually requires minimum treatment.

SURFACE WATERS: Rivers and streams, lakes and reservoirs are our principal supplies.
Surface waters:
a) are usually higher in turbidities.
b) are higher and far more variable in suspended solids.
c) usually possess some color.
d) are lower in hardness.
e) most always have microbial contamination concerns.
f) have greater changes in water quality parameters than groundwater’s.

For rivers and streams we must know and address:
a) silting,
b) ice,
c) rapidly changing water quality parameters,
d) and upstream pollution problems.

For lakes and reservoirs must know and address:
a) watershed uses in agricultural, recreation, and domestic uses;
b) stratification (layers of different temp. water) and reservoir and lake "turnover" each fall;
c) algae with taste and odor problems and algal blooms.

Reclaimed water (high quality, also means very expensive, water from advanced treatment wastewater treatment facilities) is used for non-food crop irrigation, irrigation of parks, golf courses, wetlands, and industrial reuse.

Lakes and reservoirs: Natural factors affecting water quality are fires; geology; plant and vegetation type, growth; climate, and wind. Man-made factors are agricultural activities; domestic and industrial discharges; recreational uses.

The safe yield for surface water supplies is defined as the rate of water withdrawal being less than or equal to the rate of water replenishment for the water source, over an extended period of time.

Some math:
One inch of runoff per year from a watershed area of one square mile (640 acres) is equivalent to 47,700 gallons per day flow rate, or 0.0477 million gallons per day (MGD), or a stream flow rate of 0.0737 cubic feet per second.

Surface Water : WATER QUALITY ISSUES
According to the Surface Water Treatment Rule:
a) Surface waters from streams, lakes or impounding reservoirs are to be considered unsafe for human consumption without proper treatment.
b) Even though small, spring-fed streams from pristine watersheds may yield practically clear and tasteless water, (except during the height of rain storms when a moderate amount of suspended material may be present), they will also require treatment. (Special studies may be submitted for review on a case-by-case basis for some treatment exemptions.)
c) Though any objectionable bacteria present may be of animal origin, such streams are always exposed to accidental or incidental pollution by humans, and therefore require watershed protection..

Natural Lakes
Large lakes may:
a) Yield water of fine quality except near the shore line, due to erosion, warmer temperatures and algal activity, etc. and in the vicinity of wastewater and stormwater outlets or near outlets of large streams
b) Require minimum treatment.
c) Many times the treated wastewater effluent from a city is discharged into the same lake from which the water supply is taken. The water treatment plant’s raw water intake should be located away from the wastewater plant outfall line to minimize the impact on the potable water facility.

Reservoirs
Man-made reservoirs are usually constructed to
a) be an impoundment for storage,
b) achieve a turbidity reduction by settling out during storage,
c) stabilize the raw water parameters and conditions, as compared to a large river source,
d) There may be additional benefits, such as a reduction in bacteria.
Disadvantages may include:
a) production of unpleasant tastes and odors by algae.
b) cost

Rivers
Usually, rivers require more extensive treatment than other raw water sources due to widely varying
a) turbidity,
b) mineral content,
c) temperature,
d) degree of point and non-point pollution .

Most often, a river is chosen as a water source only when other sources are not available. Raw water supplies drawn directly from a river have the advantage over an impounding reservoir, in that original costs are less because expensive land (entire watersheds in some cases), dams, pipes, permits, and water rights are not required.

Watershed and Source Water Protection

The federal Surface Water Treatment Rule and other water regulations, and the state health department regulations outline the procedures and actions required for the protection of public water supplies. These regulations specify the conditions during construction activities, stormwater runoff, construction, operation, and maintenance of wastewater treatment facilities, septic tanks, and other watershed impacting activities.

The goal is to prevent the pollution of the watershed and groundwater sources of water supply than to depend upon the effectiveness of the water treatment process to provide a safe water to our consumers.

If possible the municipality should try to purchase or control the entire watershed area , in order to protect the water source from contamination and poor land practices. Erosion control in the watershed is very beneficial in reducing the quantity of silt deposited in the lake, or reservoir. This also impacts the amount of turbidity which the treatment plant must remove.

Runoff and water impoundment activities may contain wetlands which discolor the raw water and cause taste/odor water problems. A reduction in these areas, or a channeling of their discharges away from the raw water intake is very desirable to reduce these types of problems.

Water Consumption Facts
a) Consumption in the United States averages between 60 and 300 gallons per capita per day and depends upon the size of the community, water availability, cost for the water, and area of the country that the system is in.
b) About 45 percent of the total water produced is for domestic use and about 45 percent is used for industrial and commercial purposes. (In some community’s up to 75% of the domestic water production amount is for swimming pools and landscape irrigation during the summer months.) 10 percent is for public and other uses.
c) The estimated quantity of leakage in a water distribution systems from about five percent to over 40 percent of the water produced. The average is about 10 to 15 percent.
d) The rate of consumption (water demand) varies throughout the day, and the time of year from community to community.
e) Vacaville, California (in Northern California) consumes about 6.5 MGD during the winter months when its raining, and about 21 MGD during the dry summer months. Five days in a row of ambient hot temperatures (about 105 degrees Fahrenheit) will crate a water demand of about 26 MGD.
Vacaville’s Easterly Wastewater Treatment Plant receives about 7.8 MGD during the summer and 8.2 MGD during the winter. Why would there be such a difference from what the water system delivered to the city of about 90,000 people during these parts of the year? What are the values for your community?

Consumption Information for Future Applications
We must calculate and record the rates of consumption for our system.
Important records include:
a) our treatment plant water production,
b) quantity of water we are pumping from our wells,
c) reservoir levels over time,
d) water distribution system water demands (actual amount of water consumed).

Save all records and trend charts which pertain to water production and consumption. These records are invaluable when:
a) building new homes and businesses in the community
b) planning for your treatment plant expansion
c) planning and designing a distribution system expansion.
d) planning for and designing raw water and treated water reservoir expansion

Go to Past Issues of Operator Notebook

Return to Wright's Training Homepage