DES 601 Basic Hydrology and Hydraulics
1 SEP 2013
Exercise 12. Estimate Change in Storage; Velocity in Hydraulic System
Purpose
Estimate rate of discharge from a detention basin from hydraulic continuity concepts.
Estimate change in flow velocity from change in cross sectional dimension.
Requirements
1) Pencil/Pen
2) Calculator
Exercises
1) Table 1 (next page) is a depth-area relationship for a detention basin. The pond is
initially full (depth=9 feet). The basin is drained at a constant rate of 90.75 cubic
feet per second for 24 hours. Estimate the depth of water in the pond at the end
of 24 hours.
a. Complete the table by computing the storage volumes in the basin.
𝑉𝑜𝑙 = 𝐴𝑟𝑒𝑎 ∗ 𝐷𝑒𝑝𝑡ℎ
b. Compute the volume remaining after 24 hours.
𝑉𝑜𝑙𝑟𝑒𝑚𝑎𝑖𝑛 = 𝑉𝑜𝑙𝑖𝑛𝑖𝑡𝑖𝑎𝑙 − 𝑄 ∗ 𝑇𝑖𝑚𝑒
c. Estimate from the table the depth of water remaining in the basin.
Exercise 12
Page 1 of 3
DES 601 Basic Hydrology and Hydraulics
Table 1. Depth-Area for a Detention Pond
Exercise 12
Page 2 of 3
1 SEP 2013
DES 601 Basic Hydrology and Hydraulics
1 SEP 2013
2) A rectangular channel 10 feet wide carries steady flow as depicted in Figure 1.
Using the principles of continuity determine
Figure 1. Elevation view of flow in a rectangular channel
a. The discharge at section 2
b. The mean section velocity at section 1
c. The mean section velocity at section 2
Exercise 12
Page 3 of 3