DO NOT NEED PICTURES, NUMBERS ARE THERE FOR YOU! Mono Lake Water Budget Assignme
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DO NOT NEED PICTURES, NUMBERS ARE THERE FOR YOU!
Mono Lake Water Budget Assignment
Objectives: This homework is designed to give you practice using water budgets to
solve common problems in water resource management. The homework will use actual
data from monitoring stations at Mono Lake, California. In addition, this homework
REQUIRES the use of unit conversions, correct application of significant figures,
and use of scientific notation (and you thought after high school you’d never do this
again).
Hydrology of Mono Lake
Location:
Mono Basin is an intermontane, closed drainage basin in central Mono County,
California, and Mineral County, Nevada (Figure 2).
Figure 2. Mono basin
watershed (highlighted in
yellow).
The Mono Basin is about 300
kilometers from San Francisco
(Figure 3) and forms part of the
eastern boundary of Yosemite
National Park. Lee Vining and
June Lake, CA are the only
two towns within the basin.
Figure 3. Location of
Mono Basin.
Basin Morphology:
The shape of the Mono Basin is slightly elongate northeast-southwest (Figure 1). The
area of Mono Basin is 1,800.1 km2. The area of Mono Lake is 181.3 km2.
The basin floor is relatively flat, sloping gently upward from Mono Lake at 1,948 m
(6,390 ft) to the base of the surrounding rim of mountains at about 2,200 m (7,200 ft).
West of Mono Lake, the Sierra Nevada rise abruptly from the lake and culminate in
snowy crests at elevations near 4,000 m.
Climate:
The climate of the Mono Basin is continental, with cold winters, during which most of the
annual precipitation occurs, and dry summers with hot days and cool nights. Average
annual precipitation in the basin has been recorded since the early 1950s. The average
annual precipitation for the Mono Basin is 35.5 cm.
Water Budget (Inputs-Outputs=Change in Storage):
The variables for the Mono Basin water budget include:
INPUTS: Precipitation (P), discharge from 3 creeks (Q), and groundwater inflow to
Mono Lake (G)
OUTPUTS: Evaporation (E), and water diversions from the three creeks before flowing
into Mono Lake (D)
CHANGE IN STORAGE: the change in water volume in Mono Lake (V)
Assignment
Your answers must have the correct number of significant figures and use proper
scientific notation (e.g. 1.2x106 m3/yr). All the questions are listed here, but you
must complete the Mono Lake Water Budget Assignment on iLearn.
1. Mono Basin Watershed. The Mono Basin is a(n) _____________ watershed.
a) Closed
b) Open
2. Water Budget Equation. Write the general water budget for Mono Lake using the
specific water budget terms (P, Q, G, E, D, & V).
a) P + (Q - D) + G - E = V
b) P + (Q - D) + G + E = V
c) P - (Q - D) + G + E = V
d) P + Q + D + G - E = V
e) P + (Q - D) - G - E = V
3. Mono Basin Precipitation. Calculate the average annual precipitation in cubic
meters per year (m3/yr) for Mono Basin.
a) 7.83 x 108 m3/yr
b) 7.17 x 108 m3/yr
c) 6.354 x 107 m3/yr
d) 6.35 x 108 m3/yr
e) 7.16590 x 105 m3/yr
4. Mono Lake Precipitation. Calculate the average annual precipitation in cubic
meters per year (m3/yr) for Mono Lake.
a) 6.39 x 108 m3/yr
b) 9.632 x 107 m3/yr
c) 6.40 x 104 m3/yr
d) 96320 m3/yr
e) 6.40 x 107 m3/yr
5. Evaporation from Mono Lake. The average annual lake evaporation from Mono
Lake is 1.143 m. Calculate the annual evaporation in cubic meters per year (m3/yr)
from Mono Lake.
a) 1.8 x 108 m3/yr
b) 1.792 x 108 m3/yr
c) 207225900 m3/yr
d) 2.072 x 108 m3/yr
e) 2.1 x 108 m3/yr
6. Discharge. Three large creeks flow into Mono Lake from the Sierra Nevada. These
creeks are gaged by the Los Angeles Department of Water and Power (DWP), and
have the following average annual discharge:
Lee Vining Creek 83.5 cfs (cubic feet per second (ft3/sec))
Rush Creek 42.7 cfs
Mill Creek 34.0 cfs
Calculate the combined average annual discharge of these three creeks in cubic
meters per year (m3/yr).
Note: 1 m3 = 35.3147 cubic feet (ft3), and 1 year = 31,536,000 seconds. USE THE
CORRECT ORDER OF OPERATIONS (PEDMAS).
a) 1.46 x 108 m3/yr
b) 1.51 x 108 m3/yr
c) 1.43 x 108 m3/yr
d) 1.431 x 108 m3/yr
e) 1.510 x 107 m3/yr
7. Diversions. The Los Angeles DWP has been diverting water from Lee Vining, Rush,
and Mill Creeks (below the gaging stations) for many years, running the diverted
water through the Owens Valley aqueduct to Los Angeles. These diversions average
103,408 acre-feet per year (ac-ft/yr). Note: 1 m3 = 0.000811 acre-foot.
Taking into account these diversions, calculate the average annual flow into
Mono Lake from these three creeks in cubic meters per year (m3/yr).
a) 1.28 x 108 m3/yr
b) 1.27508 x 108 m3/yr
c) 1.55 x 107 m3/yr
d) 1.2 x 107 m3/yr
e) 1.56 x 107 m3/yr
8. Change in Storage: From data recorded by the Los Angeles DWP, Mono Lake
water levels fell 15.7 feet over 10 years. Accounting for the shape of the lake
basin, the lowering of the lake level resulted in a change of storage of
-102,457,272 m3.
Calculate the average annual change in storage over this 10-year period in cubic
meters per year (m3/yr).
a) 10,245,727.2 m3/yr
b) 102,457,272 m3/yr
c) -1.02457272 x 107 m3/yr
d) -10,245,727.2 m3/yr
e) -1.03 x 107 m3/yr
9. Groundwater Inflow: Using all the data presented so far, solve the water budget
equation for average annual groundwater inflow to Mono Lake in cubic meters per
year (m3/yr). Use the precipitation value for Mono Lake (question 4), NOT the value
for the Mono Basin (question 3).
a) 17756277.3 m3/yr
b) -17756277.3 m3/yr
c) 1.8 x 108 m3/yr
d) 1.175 x 108 m3/yr
e) 1.174 x 108 m3/yr
10. Errors with Water Budget Calculations. Which of the variables of the water
budget probably contains the largest error? Think about how each variable was
calculated.
a) P
b) Q
c) D
d) E
e) G
Explanation / Answer
1. (a) closed
Mono Basin is a closed drainage basin.
2. (a) P + (Q - D) + G - E = V
Since water budget is given by
Inputs-Outputs=Change in Storage
3. (d) 6.35 x 108 m3/yr
Avg annual precipitation is given by
rainfall(in cm) x area of mono basin = 35.5 cm x 1800.1km2 = 639035500 m3
4. (e) 6.40 x 107 m3/yr
Avg annual precipitation is given by
rainfall(in cm) x area of mono lake = 35.5cm x 181.3 km2 = 64361500 m3
5. (d) 2.072 x 108 m3/yr
Annual precipitation is given by
evaporation(in meters) x area of mono lake = 1.143m x 181.3 km2 = 207225900m3
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