Environmental Engineering Reference
In-Depth Information
Approach channel and safety/debris boom
Control structure (such as crest structure or grade sill,
gates, and operating equipment, if applicable)
Conveyance feature (such as
chute and/or conduit/tunnel)
Operating bridge
N.W. S.
Radial gates
Te rminal structure and
exit channel
El. 3799.0
El. 3749.0
El. 3780.0
Dumped riprap
El. 3804.0
S = 0.05
S = 0.10
El. 3757 ±
2:1
Spillway profile
Dumped riprap
Stilling basin
FIGURE 10.26 Common features of spillways. (From USBR, Design standards No. 14, appurtenant struc-
tures for dams (spillway and outlet works), design standards, U.S. Department of the Interior, Bureau of
Reclamation, 2010.)
Conveyance features (such a upstream
and downstream conduit/tunnel)
Intake structure
Te rminal structure and
exit channel
Top of active conservation
capacity, El. 6882.0
Intake structure,
sta. 42 + 21.04
Axis of dam
Outline of dam
Original
ground surface
Access road
not shown
Control
house
Backfill
Sta. 41 + 85.0
Sill El. 6760.00
El. 6755.0
£ Gate chamber
sta. 49 + 99.00
£ S = 0.01779
£ 4-0 × 6-0 outlet gate
2:1
7-6 dia. circular tunnel
11-0 dia. horseshoe
tunnel
£ S = 0.010923
5-0 diversion pipe
5 - Conduit sections
at 14-6 = 72-6
Begin conduit
sta. 42 + 44.12
Invert El. 6730.00
End upstream tunnel
sta. 49 + 75.00
Begin downstream tunnel
Sta. 50 + 31.50
Tunnel portal
sta. 57 + 13.50
Tunnel portal
sta. 43 + 16.62
Profile along outlet works
Control structure (such as gate
chamber and access shaft)
FIGURE 10.27 Common features of outlet works. (From USBR, Design standards No. 14, appurtenant
structures for dams (spillway and outlet works), design standards, U.S. Department of the Interior, Bureau of
Reclamation, 2010.)
10.4.2.1 Functional Requirements
The outlet works of a dam depend largely upon the purpose for which the dam was designed, or
its authorized purpose, for example, lood control, conservation, or hydropower. For lood control,
the outlet structures are designed to allow high outlows; they may be gated or ungated and are
commonly surface releases. For conservation (e.g., the conservation pool, Figure 10.3), the outlet
works may vary with the speciic type of conservation practice, such as navigation, irrigation, and
water supply and may be from the surface (overlows) or from below the water surface. For meet-
ing downstream water quality targets, for example, the outlet works may allow water to be with-
drawn from different vertical levels, or from multiple levels, during the year, as the water quality
and the temperature vary seasonally and vertically within the reservoir. For hydropower, water is
discharged through a penstock to a turbine, which revolves to generate electricity (Figure 10.28).
Since the water-surface elevation provides the potential energy, the water is typically withdrawn
from the lower levels of the reservoir, frequently resulting in releases of cold(er) water often with
low dissolved-oxygen concentrations.
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