Geoscience Reference
In-Depth Information
Figure 16.36 Annual flows for the
Chattahoochee River downstream of
Buford Dam in Georgia.
Notice the
change in the variability of annual dis-
charge before and after the construc-
tion of Buford Dam in 1956. (
Source:
U.S. Geological Survey.)
Chattahoochee River
Buford Dam
70,000
GA
60,000
50,000
40,000
30,000
Buford Dam
constructed
20,000
10,000
1910
1920
1930
1940
1950
1960
1970
1980
1990
stream discharge upstream of the dam to be trapped in the res-
ervoir. The lake would become larger and progressively fill the
trunk and tributary valleys upstream. Below the dam, however,
the stream channel would be dry until it began to receive tribu-
tary discharge someplace downstream. This kind of extreme
scenario rarely occurs, however. Instead, the engineers typi-
cally maintain the normal stream discharge downstream of the
dam during a flood event or reduce it slightly to relieve pressure
downstream. This approach still causes the size of the impound-
ment upstream of the dam to grow because more water enters
the reservoir than is allowed to leave.
A nice example of flood protection through discharge
control can be seen in hydrographs from the 1993 flood at
Tescott and Niles, Kansas (Figure 16.37). These small towns lie
60,000
Saline River at Tescott, KS
50,000
Simulated
uncontrolled
discharge
40,000
Observed
controlled
discharge
30,000
20,000
10,000
0
1
6
11
16
21
26
31
July, 1993
80,000
Solomon River at Niles, KS
70,000
Simulated
uncontrolled
discharge
Solomon River at Niles, KS
60,000
Observed
controlled
discharge
50,000
40,000
30,000
20,000
10,000
0
1
6
11
16
July, 1993
21
26
31
Figure 16.37 River hydrographs from Tescott and Niles, Kansas, during the 1993 flood in the Mississippi
watershed.
