53:171 Water Resources Engineering
Problem #2
Annual Water Cycle for the Upper Mississippi River Basin
Estimates of the mean monthly precipitation P, evaporation E (or evapotranspiration),
and net runoff Q for the Upper Mississippi River basin are shown in the table
below.
| Mon |
Precip
P
(mm) |
Evap
E
(mm) |
Runoff
Q
(mm) |
| Jan |
30.6 |
6.6 |
12.3 |
| Feb |
26.5 |
14.7 |
13.6 |
| Mar |
66.6 |
24.8 |
26.2 |
| Apr |
79.4 |
34.1 |
33.7 |
| May |
98.9 |
83.7 |
31.3 |
| Jun |
102.4 |
97.4 |
22.7 |
| Jul |
90.8 |
125.8 |
18.1 |
| Aug |
104.8 |
104.6 |
11.5 |
| Sep |
76.5 |
56.2 |
11.0 |
| Oct |
61.8 |
33.1 |
11.4 |
| Nov |
50.7 |
18.1 |
12.2 |
| Dec |
38.9 |
9.9 |
14.8 |
- Compute the change in land surface DS (in mm)
for each month.
- Assume that the land surface storage S at the start of
January is 0 mm (Note: This is not the absolute storage, but an assumed
reference). Compute the storage S (in mm) at the end of each month.
- In what month is the storage S at its maximum during the year? In what
month is the storage at its minimum? What is the change in storage
DS (in mm) from the maximum to the minimum?
-
Plot the precipitation P, the evaporation E, the net runoff Q,
and the land surface storage S versus month (on a single graph). [Take a look at the results
to get a feel for changes in water availability over the year.]
- Compute the monthly runoff coefficient (net runoff as a fraction of precipitation) (in %).
Plot the runoff coefficient versus month. [Take a look at the results
─ do the variations make physical sense?].
Last changed on
01/07/14
by Gabriele Villarini.