Report of Water Loss Investigation
West Lake, El Dorado Country Club
Tucson, Arizona
by
D. G. Boyer
C. B. Cluff
Water Resources Research Center
University of Arizona
January 1971
Report of Water Loss Investigation - West Lake
El Dorado Country Club, Tucson, Arizona
Introduction
The University of Arizona Water Resources Research Center measured the water
loss in a small, artificial lake over a period of 25 days in the fall of 1970.
During construction, this man -make lake had been treated with a bio- chemical en-
zymatic product to retard seepage.
The investigation began shortly after the ini-
tial filling and included the measurement of water loss, rainfall and evaporation.
Location and Description of the Lake
Three small lakes were dug in the spring and summer of 1970 during construction of the El Dorado Country Club.
The Country Club lies to the north of Speed-
way Boulevard starting about one -half mile east of Wilmot Road in Tucson and is
adjacent to the El Dorado Lodge.
In addition to their aesthetic value the lakes
are used as temporary storage locations for irrigation water used on greens and
fairways.
They are filled by wells located on the property.
The westernmost lake was used in the investigation and was chosen because
water was first available at that location.
When full, the lake has a surface
area of approximately 35,000 square feet (0.8 acre) and its measured depth is
slightly over eleven feet.
The shape approaches that of a horseshoe with its
curved end being wider than either of the branches.
Because of the relatively sandy soil in some locations at the lake site,
finer materials (silts and
clays) were brought in from other areas of the prop-
erty and compacted to plate the sides and bottom.
uct (trade name:
A bio- chemical enzymatic prod-
Enzymatic SS) supplied by Enzymatic Soil of Tucson was added
during the process.
The enzymes (applied at a rate of one gallon to 30 or 40
cubic yards of material) were worked with the imported soil and compacted so that
plating of 8 -12 inches on the bottom and 4 -6 inches on the sides resulted.
Construction of the west lake was completed in early summer but filling
did not proceed until the beginning of September.
was subjected to several intense rain storms.
During this period the area
Runoff from the adjacent, but
uncompleted, fairways and greens washed into the lake and some rutting of the
steep sides occured.
In a few areas V- shaped cuts, several inches wide ex-
tending downward from the top of the banks were seen.
It is not known whether
the plate was completely breached by the washing action.
cuts with sand and silt occurred as runoff decreased.
Some filling of the
When first observed, the
lake was partially full and examination of the cuts below the water line was
not possible at that time.
However, later in the fall the lake was pumped to
allow screening of the pump intake.
It was then noticed that the cuts became
more shallow and less extensive as they approached the bottom.
Method of Investigation
Measurement of water loss began on September 11 and continued for 25 days
until October 6, 1970.
The investigation was conducted by using a modification
of the water budget equation:
(Sfinal
Sinitial) = Rainfall + Surface Inflow
- Surface Outflow - Infiltration (seepage) - Evaporation, where (Sfinal
- S initial)
= AS or the change in storage of the lake.
During the investigation, pumping in and out of the lake was discontinued.
The largest rainfall for a 24 hour period was only 0.24 inches.
This precipi-
tation was not as intense as earlier storms and runoff from the immediate area
into the lake was assumed to be negligible.
Therefore, the surface inflow and
outflow terms are dropped from the above equation and storage is a function of
rainfall, evaporation and infiltration alone.
If evaporation and infiltration are assumed to be inherently negative in
sign, the equation may be changed to AS = Rainfall + evaporation + infiltration.
In a sealed pan or pond, infiltration is not present and, when solved for evaporation, the equation is Evaporation = AS - Rainfall.
Upon inserting collected
data, the evaporation is found and will have the correct sign (negative).
The
methods used to find the rainfall and evaporation are discussed below.
Rainfall was measured by use of a commercially available, non -recording gage
with a 2.5 x 2.3 square -inch
opening.
It was mounted on a post about three feet
above ground level at the lake site.
Measurement of the evaporation presented a more difficult problem, however.
Since
the evaporation rate varies with air temperature, wind, vapor pressure
and solar radiation, computation using various equations and graphical solutions
would be prohibitive without installation of monitering equipment at the site.
Also, direct transfer of data that could be obtained, in part, from weather observation stations at the airport or the - University might not yield meaningful
results.
These stations are at a distance of 8 -10 miles and local weather, es-
pecially rainfall and wind, can vary .greatly during some of the late summer
storm periods.
The method decided upon was to place a standard Class A evaporation pan
(4 ft diameter, filled to 8 inches depth) above ground at the site.
Although a
pan placed above ground experiences greater evaporation than does a sunken pan
(primarily due to heat energy transfer through side walls), it was used here in
the interest of ease of installation, operation and comparison with other Class
A pans.
Additional data was obtained from a Class A pan and a 40 x 60 square -
foot, sealed 9 foot deep pond installed at the Water Resources Research Center
Field Laboratory located west of the Highway I -10, Miracle Mile interchange in
Tucson.
-4-
A daily pond -to -pan ratio of evaporation was computed using the measure-
ments obtained at that location.
for the 25 day period.
The ratio varied from a low of 0.21 to 0.99
Using evaporation for the entire period, the coefficient
was found to be 0.62 and compares favorably with the 0.60 mean annual ratio
found using data obtained from observations of Lake Mead (Water Loss Investigations, Lake Mead Studies, U. S. Geological Survey Professional Paper 298, 1958).
To estimate the lake evaporation by use of the ratio, a reading was first obAfter correcting for rainfall (if any),
tained from the Class A pan at the site.
this pan evaporation was multiplied by the ratio found for the, same time period.
The infiltration was then found by inserting the data compiled into the
water budget equation and solving for the infiltration.
sults are presented in Tables 1 and 2.
This data and the re-
A plot (figure 1) of the cumulative total
loss due to seepage versus date was made using lake evaporation found by the
above method (line a) and, as a comparison, by direct transfer of pond evaporation data from the field laboratory (line b).
As can be seen, the loss during
the first 8 -10 days causes the cumulative total to rise rapidly.
Around Sep-
tember 24, the curve levels off and a straight line can be drawn fitting the
points plotted after that date.
The slope of that line (Ay/Ax) gives the av-
erage daily loss for that time period.
This was found to be -0.29 inches per
day for seepage computed using both the pond -to -pan coefficient and the pond
evaporation.
As given by Darcy °s Law, the rate of flow through a porous media is directly
proportional to the head loss.
Therefore, the rate of infiltration at the lake
varies directly with the decrease of head due to the total water loss.
The loss
due to infiltration was recalculated for the initial lake level (5.4 feet) with
the results drawn on figure 2.
Again, readings taken after September 21 generally
plot in a straight line for cumulative loss using both the pond -to -pan method
and the field laboratory pond for estimating evaporation.
The rates for both
methods are graphically found to be -0.39 inches per day.
Interpretation of Results
Some tentative conclusions can be drawn from the investigation.
It appears
that after the September 22 -24 period, the rate of water lost due to seepage became relatively constant.
The final rate of loss was about -0.29 inches per day
before application of the head loss correction and -0.39 inches per day when head
loss is included in the calculations.
The change to a constant value for the
rate of loss in each case may be possibly explained by the water level dropping
below the severest areas of rutting in the lake banks.
Definite determination
of this as a cause would require filling and further observation with accompanying cessation of pumping.
This is unlikely since the lake is actively used in
golf course irrigation.
The exact effect on water loss due to treatment with the enzymatic product
is not known.
The soil on the banks was observed to be cemented to some extent
by application of the chemical and this most likely retarded water loss.
It is
not known to what extent seepage would have been minimized had compaction without the enzymatic treatment been used in the plating process.
Since this in-
vestigation was limited as to both time and lack of a control lake for comparison of water loss, no conclusive judgement can be made here as to the effectiveness of this type of treatment versus compaction alone.
In a years time the seepage loss (calculated at -0.39 inches per day for
the initial level of 5.4 feet) will be approximately 12 feet or 3.1 million gallons for the 0.8 acre lake.
Therefore, the success of the treatment applied at
the El Dorado Country Club would have to be evaluated as a function of the cost
of the water lost versus the cost of an alternative treatment.
Acknowledgement
The following people assisted in the collection of information for this report.
Mr. Henry Roahrig of Blanton & Co., Architects and Engineers, Tucson, fur-
nished information on lake design and its source of water.
Bob Gilliand and
Robert Mundell of Enzymatic Soil of Tucson provided material on the preparation
and application of their product to the lake.
David Rudis and Arthur Avenetti
helped in the collection of data.
Appreciation is also extended to Richard Kubiak and Elmo O'Shannon who discontinued pumping of the lake while data collection proceeded.
Special thanks
are extended to the El Dorado Lodge and Country Club for their permission to use
the golf course lake in this investigation.
-0.614
-0.344
-0.724
-0.586
-0.239
0.025
0.13
-0.614
-0.344
-0.724
-3.436
-0.750
+0.017
-0.586
-0.239
17
19
21
29
10- 2
3
5
6
Notes:
-0.703
-0.703
-0.180
-0.312
+0.072
-0.360
-2.364
-0.396
-0.276
-0.420
-0.540
+0.240
AS
Table 1:
2lnitial readings begun 9- 11 -70.
'All readings are inches.
-0.113
-0.775
-3.436
-0.676
15
0.38
-0.296
Evap.
9-132
Rain
oS1
(1970)
Date
PAN
-0.180
-0.312
-0.058
-0.385
-2.364
-0.396
-0.276
-0.420
-0.540
-0.140
Evap.
0.75
0.53
0.51
0.50
0.69
0.55
0.80
0.68
0.77
0.21
Pan Ratio
Pond -to-
Rainfall and Evaporation Data
0.13
0.025
0.38
Rain
POND
FIELD LABORATORY
-0.348
-0.357
+0.125
-0.750
-3.337
-0.801
-1.336
-0.800
-0.803
-0.643
AS
DORADO
0.24
0.12
0.04
Rain
PAN
-0.348
-0.357
-0.115
-0.870
-3.337
-0.801
-1.336
-0.800
-0.803
-0.683
Evap.
-0.26
-0.19
-0.06
-0.44
-2.30
-0.44
-1.07
-0.54
-0.62
-0.14
Evap.
using
Ratio
Adjusted
COUNTRY CLUB
EL
1
-5.36
-7.46
-9.46
-11.19
-17.43
-17.37
-18:12
-18.74
-2.57
-2.10
-2.00
-1.73
-4.80
-1.44
+0.06
-0.75
-0.62
15
17
19
21
29
10- 2
3
5
6
Notes:
-2.79
-2.79
9-13
0.24
0.12
0.04
Rain
-0.36
-0.56
-0.12
-1.12
-2.50
-1.29
-0.93
-1.56
-1.95
-2.69
Infilt.2
-13.08
-12.72
-12.16
-12.04
-10.92
-8.42
-7.13
-6.20
-4.64
-2.69
-0.44
-0.44
-0.12
-1.18
-2.44
-1.33
-1.72
-1.68
-2.03
-2:69
Infilt.3
DORADO
(line á)
Cumul.
Total
EL
-14.07
-13.63
-13.19
-13.07
-11.89
-9.45
-8.12
-6.40
-4.72
-2.69
Cumul.
Total
(line b)
LAKE
-0.50
-0.77
-0.16
-1.53
-3.31
-1.56
-1.09
-1.76
-2.12
-2.81
Infilt.4
-15.61
-15.11
-14.34
-14.18
-12.65
-9.34
-7.78
-6.69
-4.93
-2.81
Cumul.
Total
(line e)
-0.62
-0.61
-0.16
-1.61
-3.23
-1.60
-2.01
-1.90
-2.21
-2.81
Infilt.5
Table 2:
Infiltration (loss due to seepage), West El Dorado Lake
'All readings are inches.
2lnfiltration computed from adjusted evaporation using Pond -to -Pan ratio, Infil. = AS - (R) - (E).
3lnfiltration computed using only Field Laboratory pond evaporation.
'+Infiltration computed from adjusted evaporation using Pond -to -Pan ratio; corrected for head loss.
5lnfiltration computed using only Field Laboratory pond evaporation; corrected for head loss.
-15.99
AS
AS'
Cumul.
Date
(1970)
WEST
-16.76
-16.14
-15.53
-15.37
-13.76
-10.53
-8.93
-6.92
-5.02
-2.81
Cumul.
Total
(line d)
-16
-12
Loss due to
Infiltration
(Cumulative
total inches)
b
a
6
Total water loss due to seepaCe vs. date.
Final rate:
-0.29 in. /day
Total water loss due to seepage vs. date.
(Infiltration for this curve computed
using only Field Laboratory pond evaporation data.) Final rate:
-0.29 in. /day
o
9,7;13
17
21
25
Date
Figure 1:
29
(Month -Day, 1970)
Loss due to Infiltration vs. Date
10-3
7
-10-
-16
-14
d
-12
Loss due to
Infiltration
(Cumulative
total inches)
-10
Total water loss due to seepage vs. date.
(Corrected for head loss)
Final rate:
-0.39 in. /day
Total water loss due to seepage vs. date.
(Corrected for head loss; infiltration for
this curve computed using only Field
Laboratory pond evaporation data.)
Final rate:
-0.39 in. /day
f
0
1
9-13
17
21
25
Date
Figure 2:
29
(Month-day, 1970)
Loss due to Infiltration vs. Date
(Corrected for head loss)
10-3
7.