Lin S.D. Water and Wastewater Calculations Manual

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These procedures allow lake and pan evaporation to be computed from

four items of climate data, i.e. air temperature, dew point temperature,

wind movement, and solar radiation. Since long-term climate data are

mostly available, these techniques permit extended and refined evapo-

ration determination.

Although the nomograph (Fig. 2.3) was developed for the use with

daily values, it is also usable with monthly average values and gives rea-

sonably reliable results with annual average values. The four-quadrant

diagram can be used to determine a lake’s evaporation rate as illustrated

in Fig. 2.3. For example, at the upper left quadrant, a horizontal line

passes from the mean daily air temperature 81°F to the first intersec-

tion at the solar radiation 600-langley curve, and projects toward the

right to intersection of the 55°F mean daily dew point curve. At this stop,

a vertical line runs downward to the line of 120-miles per day wind

movement from where a horizontal line projects toward to the left to

intersect a vertical line from the first intersection. The average daily lake

evaporation, 0.27/in, is read at this point.

The following two equations for evaporation can be computed by com-

puter (Lamoreux, 1962) as exemplified by the Weather Bureau compu-

tational procedures for the United States.

For pan evaporation:

⫽ {exp[(T

⫺ 212)(0.1024 ⫺ 0.01066 ln R)] ⫺ 0.0001

⫹ 0.025(e

⫺ e

)

0.88

(0.37 ⫹ 0.0041 U

)} ⫻ {0.025 ⫹ (T

⫹ 398.36)

⫺2

⫻ 4.7988 ⫻ 10

exp[⫺7482.6/(T

⫹ 398.36)]}

⫺1

(2.11)

For lake evaporation, the expression is

⫽ {exp[(T

⫺ 212)(0.1024 ⫺ 0.01066 ln R)] ⫺ 0.0001 ⫹ 0.0105(e

⫺ e

)

0.88

⫻ (0.37 ⫹ 0.0041U

)} ⫻ {0.015 ⫹ (T

⫹ 398.36)

⫺2

6.8554 ⫻ 10

⫻ exp[⫺7482.6/(T

⫹ 398.36)]}

⫺1

(2.12)

where E

⫽ pan evaporation, in

⫽ lake evaporation, in

⫽ air temperature, °F

⫽ vapor pressure, inches of mercury at temperature T

⫽ dew point temperature, °F

R ⫽ solar radiation, langleys per day

⫽ wind movement, miles per day

Pan evaporation is used widely to estimate lake evaporation in the

United States. The lake evaporation E

is usually computed for yearly

Lakes and Reservoirs 135

time periods. Its relationship with the pan evaporation E

can be

expressed as

(2.13)

where p

is the pan coefficient. The pan coefficient on an annual basis

has been reported as 0.65 to 0.82 by Kohler et al. (1955).

Robert and Stall (1967) used Eqs. (2.9) and (2.10) for 17 stations in and

near Illinois over the May–October season for a 16-year period to develop

the general magnitudes and variability of lake evaporation in Illinois.

Evaporation loss is a major factor in the net yield of a lake or reser-

voir. The net evaporation loss from a lake is the difference between a

maximum expected gross lake evaporation and the minimum expected

precipitation on the lake surface for various recurrence intervals and for

critical periods having various durations. This approach assumes max-

imum evaporation and minimum precipitation would occur simultane-

ously. The following example illustrates the calculation of net draft rate

for a drought recurrence interval of 40 years.

Example: Calculate the net yield or net draft for the 40-year recurrence

interval for a reservoir (333 acres, 135 ha). Given: drainage area ⫽ 15.7 miles

unit reservoir capacity (RC) ⫽ 2.03 in, draft ⫽ 1.83 MGD, E ⫽ 31 in/acre.

solution:

Step 1. Compute reservoir capacity in million gallons (Mgal)

RC ⫽ 2.03 in ⫻ 15.7 miles

⫽ 2.03 in ⫻ (1 ft/12 in) ⫻ 15.7 miles

⫻ (640 acres/miles

)

⫽ 1700 acre ⭈ ft

⫽ 1700 acre ⭈ ft ⫻ 43,560 ft

/acre ⫻ 7.48 gal/ft

⫽ 554 Mgal ⫽ 2,097,000 m

Note: 1 Mgal ⫽ 3785 m

Step 2. Compute the total gross draft, the duration of critical drawdown

period for 40-year recurrence interval is 16 months

16 months ⫽ 365 days/12 ⫻ 16 ⫽ 486 days

Draft ⫽ 1.83 MGD ⫻ 486 days

⫽ 888 Mgal

Step 3. Compute the inflow to the reservoir (total gross draft minus RC)

Inflow ⫽ draft ⫺ RC ⫽ 888 Mgal ⫺ 554 Mgal

⫽ 334 Mgal

5 p

136 Chapter 2

Step 4. Compute the evaporation loss E

Effective evaporation surface area of the lake is 333 acres ⫻ 0.65 ⫽ 216 acres

E ⫽ 31 in ⫻ (1 ft/12 in) ⫻ 216 acres

⫽ 558 acre ⭈ ft

⫽ 182 Mgal

Step 5. Compute the net usable reservoir capacity (the total reservoir capac-

ity minus the evaporation loss)

RC ⫺ E ⫽ 554 Mgal ⫺ 182 Mgal

⫽ 372 Mgal

Step 6. Compute the total net draft which the reservoir can furnish (the net

usable reservoir capacity plus the inflow)

Net draft ⫽ 372 Mgal ⫹ 334 Mgal

⫽ 706 Mgal

Step 7. Compute the net draft rate, or the net yield, which the reservoir can

furnish (the total net draft divided by total days in the critical period)

Net draft rate ⫽ 706 Mgal/486 days

⫽ 1.45 MGD

⫽ 5490 m

Note: 1 MGD ⫽ 3785 m

5 The Clean Lakes Program

In the 1960s, many municipal wastewater treatment plants were con-

structed or upgraded (point source pollution control) in the United

States. However, the nation’s water quality in lakes and reservoirs has

not been improved due to nonpoint sources of pollution. In 1972, the

US Congress amended Section 314 of the Federal Water Pollution

Control Act (Public Law 92-500) to control the nation’s pollution

sources and to restore its freshwater lakes. In 1977, the Clean Lakes

Program (CLP) was established pursuant to Section 314 of the Clean

Water Act. Under the CLP, publicly owned lakes can apply and receive

financial assistance from the US Environmental Protection Agency

(US EPA) to conduct diagnostic studies of the lakes and to develop fea-

sible pollution control measures and water quality enhancement tech-

niques for lakes. This is the so-called Phase 1 diagnostic/feasibility

(D/F) study.

Lakes and Reservoirs 137

The objectives of the CLP are to (US EPA, 1980):

1. classify publicly owned freshwater lakes according to trophic

conditions;

2. conduct diagnostic studies of specific publicly owned lakes, and

develop feasible pollution control and restoration programs for them;

and

3. implement lake restoration and pollution control projects.

5.1 Types of funds

The CLP operates through four types of financial assistance by cooper-

ative agreements. They are

State lake classification survey

Phase 1—diagnostic/feasibility study

Phase 2—implementation

Phase 3—post-restoration monitoring

Funding is typically provided yearly for the state lake classification

survey, but on a long-term basis for Phases 1, 2, and 3. Phase 1 funds

are used to investigate the existing or potential causes of decline in the

water quality of a publicly owned lake; to evaluate possible solutions to

existing or anticipated pollution problems; and to develop and recom-

mend the most “feasible” courses of action to restore or preserve the

quality of the lake. Activities typically associated with sample collection,

sample analyses, purchase of needed equipment, information gathering,

and report development are eligible for reimbursement. During Phase

1, total project costs cannot exceed $100,000. Fifty percent of this fund-

ing will come from the CLP, while the rest must come from nonfederal

or local sources.

5.2 Eligibility for ﬁnancial assistance

Only states are eligible for CLP financial assitance, and cooperative

agreements will be awarded to state agencies. A state may in turn

make funds available to a substate agency or agencies for all or any

portion of a specific project. The D/F study is generally carried out by

a contracted organization, such as research institutes or consulting

engineers.

For nearly two decades, 46% of the US lake acres were assessed for

their water qualities and impairments (US EPA, 1994). Since the

early 1990s, federal funds for CLP were terminated due to the budget

cuts. Some states, such as Illinois, continued the CLP with state

funds.

138 Chapter 2

5.3 State lake classiﬁcation survey

In general, most states use state lake classification survey funding to

operate three types of lake survey activities. These include the volun-

teer lake monitoring program (VLMP), the ambient lake monitoring

program (ALMP), and lake water quality assessment (LWQA) grant. All

three programs are partially supported by a Section 314 Federal CLP

LWQA grant. State funds matched equally with federal grant funds are

used to improve the quantity and quality of lake information reported

in the annual 305(b) report to the US Congress.

Volunteer lake monitoring program. The VLMP is a statewide cooperative

program which volunteers to monitor lake conditions twice a month

from May through October and transmit the collected data to the state

agency (EPA or similar agency) for analysis and report preparation. In

Illinois, the VLMP was initiated by Illinois Environmental Protection

Agency (IEPA) in 1981 (IEPA, 1984). The volunteers can be personnel

employed by the lake owner (a water treatment plant, Department of

Conservation or other state agency, city, lake association, industry, etc.),

or they can be local citizens. (The lakes monitored are not limited to pub-

licly owned lakes.) Volunteers must have a boat and an anchor in order

to perform the sampling. Volunteers receive a report prepared by the

state EPA, which evaluates their sampling results.

Volunteers measure Secchi disc transparencies and total depths at

three sites in the lake. For reservoirs, site 1 is generally located at the

deepest spot (near the dam); site 2 is at midlake or in a major arm; and

site 3 is in the headwater, a major arm, or the tributary confluence. The

data are recorded on standard forms. In addition, the volunteers also

complete a field observation form each time the lake is sampled and

record the number that best describes lake conditions during sampling

for each site on the lake. Observations include color of the water, the

amount of sediment suspended in the water, visible suspended algae,

submerged or floating aquatic weeds, weeds near the shore, miscella-

neous substances, odors, cloudiness, precipitation, waves, air tempera-

ture at the lake, lake water levels, recreational usage, and lake

management done since the last sampling (IEPA, 1983).

Ambient lake monitoring program. The ALMP is also a statewide regular

water quality monitoring program. Water quality samples are collected

and analyzed annually by IEPA personnel on selected lakes throughout

the state. The major objectives of the ALMP are to (IEPA, 1992):

䊏 characterize and define trends in the condition of significant lakes in

the state;

䊏 diagnose lake problems, determine causes/sources of problems, and

provide a basis for identifying alternative solutions;

Lakes and Reservoirs 139

䊏 evaluate progress and success of pollution control/restoration

programs;

䊏 judge effectiveness of applied protection/management measures and

determine applicability and transferability to other lakes;

䊏 revise and update the lake classification system; and

䊏 meet the requirements of Section 314 CLP regulation and/or grant

agreements.

The ALMP provides a much more comprehensive set of chemical analy-

ses on the collected water samples than does the VLMP.

In Illinois, the ALMP was initiated in 1977. Water samples are ana-

lyzed for temperature, dissolved oxygen, Secchi disc transparency, alka-

linity, conductivity, turbidity, total and volatile suspended solids,

dissolved and total phosphorus, and nitrogen (ammonia, nitrite/nitrate,

and total kjeldahl). In addition, 9 metals and 11 organics analyses are

performed on water and sediment samples.

Lake water quality assessment. The LWQA grant is focused on non-

routinely monitored lakes to gather basic data on in-lake water quality

and sediment quality. This information increases the efficiency, effec-

tiveness, and quality of the state EPA’s lake data management and

305(b) report.

LWQA fieldwork involves two major tasks: namely, collection of lake

assessment information and in-lake water and sediment sampling.

Lake assessment information collected includes lake identification

and location, morphometric data, public access, designated uses and

impairments, lake and shoreline usages, watershed drainage area usage,

water quality and problems, status of fisheries, causes and sources of

impairment (if any), past lake protection and management techniques,

and lake maps.

In general, only one sampling trip per lake is made in order to

evaluate a maximum number of lakes with the limited resources. The

water and sediment samples are collected in summer by contracted

agencies and analyzed by the state EPA laboratory. Chemical analyses

for water and sediment samples are the same as in the ALMP.

5.4 Phase 1: Diagnostic/feasibility study

A diagnostic/feasibility study is a two-part study to determine a lake’s cur-

rent condition and to develop plans for its restoration and management.

Protocol for the D/F study of a lake (Lin, 1994) is a digest from the CLP

Guidance Manual (US EPA, 1980).

140 Chapter 2

For a Phase 1 D/F study, the following activities should be carried out

and completed within 3 years (US EPA, 1980):

1. Development of a detailed work plan

2. Study of the natural characteristics of the lake and watershed

3. Study of social, economic, and recreational characteristics of the

lake and watershed

4. Lake monitoring

5. Watershed monitoring

6. Data analysis

7. Development and evaluation of restoration alternatives

8. Selection and further development of watershed management

plans

9. Projection of benefits

10. Environmental evaluation

11. Public participation

12. Public hearings (when appropriate)

13. Report production

Activities 1 through 6 are part of the diagnostic study; the other activ-

ities pertain to the feasibility study.

Diagnostic study. The diagnostic study is devoted to data gathering

and analysis. It involves collecting sufficient limnological, morphologi-

cal, demographic, and socioeconomic information about the lake and its

watershed.

The study of lake and watershed natural characteristics, and most of

the social, economic, and recreational information of the lake region

can often be accomplished by obtaining and analyzing secondary data,

i.e. data already available from other sources.

Baseline limnological data include a review of historical data and

1 year of current limnological data. Lake monitoring is expensive.

Monthly and bimonthly samples are required for assessing physical

and chemical characteristics. At least three sites are chosen for each

lake, as mentioned in the discussion of the ALMP (Section 5.3). In

addition, biological parameters, such as chlorophylls, phytoplankton,

zooplankton, aquatic macrophytes, indicator bacteria, benthic macroin-

vertebrate, and fish surveys, must be assessed at different specified

frequencies. At least one surficial and/or core sediment sample and

Lakes and Reservoirs 141

water sample at each site must be collected for heavy metals and organic

compounds analyses. Water quality analyses of tributaries and ground-

water may also be included, depending on each lake’s situation.

Watershed monitoring is done by land-use stream monitoring manu-

ally or automatically to determine the nutrient, sediment, and hydraulic

budget for a lake.

Primary and secondary data collected during the diagnostic study

are analyzed to provide the basic information for the feasibility portion

of the Phase 1 study. Data analysis involves:

1. inventory of point source pollutant discharges;

2. watershed land use and nonpoint nutrient/solids loading;

3. analyses of lake data—water and sediment quality;

4. analyses of stream and groundwater data;

5. calculating the hydrologic budget of the watershed and lake;

6. calculating the nutrient budget of the lake;

7. assessing biological resources and ecological relationships—lake

fauna, terrestrial vegetation, and animal life;

8. determining the loading reductions necessary to achieve water qual-

ity objectives.

The following analyses of lake data are typically required: (1) identifi-

cation of the limiting nutrient based on the ratio of total nitrogen to total

phosphorus; (2) determination of the trophic state index based on total

phosphorus, chlorophyll a, Secchi depth, and primary productivity;

(3) calculation of the fecal coliform to fecal streptococcus ratios to iden-

tify causes of pollution in the watershed; and (4) evaluation of the sed-

iment quality for the purpose of dredging operations.

A description of the biological resources and ecological relationships

is included in the diagnostic study based on information gathered from

secondary sources. This description generally covers lake flora (terres-

trial vegetation, such as forest, prairie, and marsh) and fauna (mam-

mals, reptiles and amphibians, and birds).

Feasibility study. The feasibility study involves developing alternative

management programs based on the results of the diagnostic study.

First, existing lake quality problems and their causes should be identi-

fied and analyzed. Problems include turbid water, eroding shorelines,

sedimentation and shallow water depths, low water levels, low dissolved

oxygen levels, excessive nutrients, algal bloom, unbalanced aquatic veg-

etative growth (excessive growth of macrophytes), nonnative exotic

species, degraded or unbalanced fishery and aquatic communities, bad

142 Chapter 2

taste and odor, acidity, toxic chemicals, agricultural runoff, bacterial

contamination, poor lake esthetics, user conflicts, and negative human

impacts.

Once the lake problems have been defined, a preliminary list of cor-

rective alternatives needs to be established and discussed. Commonly

adopted pollution control and lake restoration techniques can be found

in the literature (US EPA, 1980, 1990). The corrective measures include

in-lake restoration and/or best management practices in the watershed.

Each alternative must be evaluated in terms of cost; reliability; techni-

cal feasibility; energy consumption; and social, economic, and environ-

mental impacts. For each feasible alternative, a detailed description of

measures to be taken, a quantitative analysis of pollution control effec-

tiveness, and expected lake water quality improvement must be

provided.

There are usually many good methods of achieving specific objectives

or benefits. The Phase 1 report should document the various alterna-

tives by describing their relative strengths and weaknesses and show-

ing how the one chosen is superior. Final selection should be discussed

in a public meeting.

Once an alternative has been selected, work can proceed on develop-

ing other program details required as part of Phase 1. These include

developing the Phase 2 monitoring program, schedule and budget, and

source of nonfederal funds; defining the relationship of Phase 2 plans

to other programs; developing an operation and maintenance plan; and

obtaining required permits. In other words, the feasibility study portion

of the Phase 1 report actually constitutes the proposal for Phase 2 study.

The report also must include the projection of the project benefits, envi-

ronmental evaluations, and public participation.

Final report. The final report will have to follow strictly the format and

protocol stipulated in the Clean Lakes Program Guidance Manual.

Requirements for diagnostic feasibility studies and environmental eval-

uations are at a minimum, but not limited, as follows:

1. Lake identification and location

2. Geologic and soils description of drainage basins

a. Geologic description

b. Groundwater hydrology

c. Topography

d. Soils

3. Description of public access

4. Description of size and economic structure of potential user

population

Lakes and Reservoirs 143

5. Summary of historical lake uses

6. Population segments adversely affected by lake degradation

7. Comparison of lake uses to uses of other lakes in the region

8. Inventory of point-source pollution discharges

9. Land uses and nonpoint pollutant loadings

10. Baseline and current limnological data

a. Summary analysis and discussion of historical baseline limno-

logical data

b. Presentation, analysis, and discussion of 1 year of current lim-

nological data

c. Tropic condition of lake

d. Limiting algal nutrient

e. Hydraulic budget for lake

f. Nutrient sediment budget

11. Biological resources and ecological relationships

12. Pollution control and restoration procedures

13. Benefits expected from restoration

14. Phase II monitoring program

15. Schedule and budget

16. Source of matching funds

17. Relationship to other pollution control programs

18. Public participation summary

19. Operation and maintenance plan

20. Copies of permits or pending applications

21. Environmental evaluation

a. Displacement of people

b. Defacement of residential area

c. Changes in land use patterns

d. Impacts on prime agricultural land

e. Impacts on parkland, other public land and scenic resources

f. Impacts on historic, architectural, archaeological, or cultural

resources

g. Long range increases in energy demand

h. Changes in ambient air quality or noise levels

i. Adverse effects of chemical treatments

j. Compliance with executive order 11988 on floodplain manage-

ment

k. Dredging and other channel bed or shoreline modifications

144 Chapter 2