Page 64 - Water Engineering Hydraulics, Distribution and Treatment

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Water Sources: Surface Water
Chapter 2
c = a coefficient with a value varying from 0.43 through 1.7 to
In some parts of the United States, the volume of silt V in
2.4
s
4.8 for low, average, and high deposition, respectively
acre-ft deposited annually can be approximated by the following
equation:
n = a coefficient to be determined specifically for a target
n
drainage area
V = c(A)
s
where
A research team has investigated two drainage areas in the
2
A = drainage area, mi
c = 0.43 for low deposition; 1.7 for average deposition; 4.8 for
volumes of their annually deposited silts. The following are the field
high deposition
data collected by the researchers using English units:
n = 0.77 for southwestern streams
For drainage area 1:
Determine the volume of silt accumulations for drainage area,
6
2
2
A = 380 mi = 984.2 × 10 m
2
2
where A, c,and n are 40 mi (103.60 km ), 1.7, and 0.77, respec- southwestern region of the United States, and has measured the
1
tively. V = 165 acre-ft = 203,528 m 3
s1
2.5 The volume of silt deposited annually can be approximated
by the following equation: For drainage area 2:
6
V = 1,233.5c[A∕(2.59 × 10 )] n 2 6 2
s A = 250 mi = 647.5 × 10 m
2
where V = 120 acre-ft = 148,020 m 3
s1
V = volume of silt deposited annually, m 3 Determine the coefficients of c and n for the southwestern
s
A = the size of the drainage area, m 2
region of the United States.
c = a coefficient with a value varying from 0.43 through 1.7 to
2.9 A spillway weir has an unobstructed crest length of 20 ft
4.8 for low, average, and high deposition, respectively (6.1 m) and a coefficient of discharge equal to 5.50. If the design
n = a coefficient to be determined specifically for a target water head is 0.75 ft (0.23 m), what is the rate of discharge?
drainage area 2.10 A house for a family of four people has minimum drinking
and culinary requirements of 25 gpcd (95 Lpcd). The mean annual
3
Determine the volume of silts deposited annually V in m , rainfall is 50 in./year (127 cm/year) and the effective period between
s
6
assuming it is known that c = 1.7, n = 0.77, and A = 648 × 10 m 2 rainy periods is 150 days. Determine (a) the size of the required
(160,119 acres).
rainfall collection cistern and (b) the size of the required catchment
2.6 Using the same metric equation from Problem 2.5 of V = area.
s
n
6
1,233.5c[A∕(2.59 × 10 )] and assuming c = 1.7, n = 0.77, and 2.11 Define the following technical terms: (a) draft; (b) eutroph-
6
2
drainage area = 984 × 10 m (243,143 acres), determine the vol- ication; (c) sublimation; (d) condensation; and (e) infiltration.
ume of silt deposited annually.
2.7 A research team has investigated two drainage areas in the
southwestern region of the United States, and has measured the
volumes of their annually deposited silts. The following are the field REFERENCES
data collected by the researchers using the metric units:
American Society of Civil Engineers, Design and Construction of
For drainage area 1: Dams, Reston, VA, 1967.
2
6
A = 984 × 10 m = 243,143 acres = 379.8mi 2 Bradley, J. N., Wagner, W. E., and Peterka, A. J., Morning-glory
1
shaft spillways, a symposium, Transactions of the American
3
V = 203,000 m = 164.6 acre-ft
s 1 Society of Civil Engineers, vol. 121, p. 312, 1956.
For drainage area 2: Department of Water Supply website, County of Maui, Hawaii,
6
2
A = 648 × 10 m = 160,119 acres = 250 mi 2 http://co.maui.hi.us/index.aspx?NID=126, 2014.
2
Fair, G. M., Geyer, J. C., and Okun, D. A., Water and Wastewater
3
V = 147,000 m = 119.17 acre-ft Engineering, vol. 1: Water Supply and Wastewater Removal,
s2
Determine the coefficients of c and n for the southwestern John Wiley & Sons, Inc., New York, 1966.
region of the United States. Fair, G. M., Geyer, J. C., and Okun, D. A., Elements of Water Supply
2.8 The volume of silt deposited annually can be approximated and Wastewater Disposal, John Wiley & Sons, Inc., New York,
by the following equation using English units: 1971.
Hazen, A., as revised by Richard Hazen, in Abbott, R. W. (editor),
V = c(A) n American Civil Engineering Practice,vol.2,JohnWiley&
s
where Sons, Inc., New York, 1956, p. 18-09.
Ippen, A. T., Channel transitions and controls, in Engineering
V = volume of silt deposited annually, acre-ft Hydraulics, Rouse, H. (editor), John Wiley & Sons, Inc., New
s
A = the size of the drainage area, mi 2 York, pp. 534–535.