The Unpredictable Osage River
Consider the two main types of river
dams, the traditional impounded pool type such as Bagnell Dam, and so-called
“run-of-the-river” type represented by the classic water wheel. Run-of-the-river (RoR) dams operate without
impounding water and energy production is completely dependent upon available
river flow, vulnerable to seasonal conditions.
While RoR type dams may arguably have less impact on the environment,
their potential operational inconsistency make them more suitable for private
use rather than commercial energy production.
Traditional impounding dams are more versatile and allow energy
production to be tailored to accommodate changing demands on the power grid
regardless of temporary water conditions. Although these two dam design
approaches seem radically different, their capacity to generate relies
ultimately on the same criteria, the average inflow of water over time. While traditional dams use impounded water to
regulate source water and produce energy on demand during periods of irregular
river flow, they are ultimately restricted to daily flow rates in order to
avoid significantly reducing vital head height. A properly designed
hydroelectric dam does not operate with flow rates that are consistently
greater than what can be replenished by sources such as rain, ground springs,
and watershed.
The character of the Osage River had been long known by indigenous Native Americans and early pioneers by the late 19th century, including its capacity to flood intensely. Prior to the design of the dam, as recently at 1895, flooding along the Osage devastated areas in Miller County.  |
| Photo Courtesy of Secretary of State Archives |
In the above photo we see one leg of the turbine gantry providing perspective on how high the Osage river was, and the torrential current. Damage to communities below was devastating.
 |
| Photo Courtesy of Secretary of State Archives |
To better appreciate a flow rate of
240,000cfs through Bagnell Dam consider that each of the 12 non-generating flood gates of Bagnell Dam are capable of releasing
13,503cfs, for a total flow rate of 162,036cfs. This means the bulk of the remaining flow of approximately 80,000cfs had to pass through the
generating facility at a rate nearly twice the allowed maximum.
With unpredictable inflow rates, and a desire to help control flooding (as originally envisioned) an impounding dam was the obvious choice for damming
the Osage, but capacity planning for electrical power generation was also
needed. How can we determine the amount of power flowing
water can generate?
