06 July 2011

An American Wivenhoe

Long-time readers may remember discussions here earlier this year about the management of the Wivenhoe Dam near Brisbane, Australia and the role of such management in the flooding of Brisbane.  One of the issues in that flooding was the role of reservoir management in the magnitude of the flood, which I described as follows:
Wivenhoe Dam near Brisbane, Australia is at the center of controversy in its role in the recent flood. The dam, as is commonly the case, is expected to serve two seemingly contradictory functions.  On the one hand it is a buffer against drought, meaning that it is desirable to keep it more full in the eventuality of low precipitation.  On the other hand, the dam is a buffer against floods, meaning that it is desirable to keep it more empty in the eventuality of heavy precipitation.  Since keeping the reservoir full and empty are not simultaneously possible, it then is necessary to balance these objectives.  Since future precipitation is uncertain, the dam's management is thus a matter of decision making under uncertainty (where risks are known) and ignorance (where they are not).
A reader (thanks DB!) passes on a lengthy article from the Great Plains Examiner out of Bismark-Mandan, North Dakota on the management of upper basin reservoirs on the Missouri River.  The article describes a decision context and outcome remarkably similar to what we saw in Australia earlier this year.
The period between March 20 and May 6 has been difficult for the Army Corps of Engineers to explain. During that span, the Corps’ water managers kept river levels low and stockpiled near-record amounts of water behind the three upper basin dams on the Missouri River, despite evidence that the Rocky Mountains were holding a lot more snow than normal.

The reservoirs were so full by early May that they couldn’t contain the late-spring rainfall that pounded Montana and the Dakotas.

Public records studied by the Great Plains Examiner show Fort Peck, Garrison and Oahe dams each were holding more than 99 percent of their total water capacity in late April. Lake Sakakawea, the largest reservoir along the river, had risen 10 feet into the flood-control zone before the Corps of Engineers began ramping up release rates from Garrison Dam to create storage space for the heavy rain and melting snow.

Emergency releases from the reservoirs in June flooded communities along a 1,700-mile stretch of the Missouri River. Almost immediately, people who live in the watershed accused federal water managers of mismanagement, officials with the Corps of Engineers pointed at their operations manuals . . . They said the problem wasn’t how they managed the reservoirs; instead, they blamed a set of conflicting congressional mandates and pressure from political leaders up and down the river system to manage the water for special interests including recreational boaters, environmentalists and the energy industry.
The article includes a remarkable admission from Jody Farhat, the chief water manager for the Missouri River reservoir system:
By the end of April, Lake Sakakawea had risen to near-record levels and the Corps of Engineers realized for the first time that the mountains were holding about 40 percent more snow than average. Until then, the Corps was expecting about 10 percent more snow than normal, Farhat said.

“By May 1, we were going ‘Holy smokes, this is not just a little-above-normal water year. It’s way above normal,’” she said.
Wow.

Larry Larson asks a question to which I suspect he has an answer:
“What were they doing in the winter months and early spring when this was building?” asked Larry Larson, executive director of the Association of State Floodplain Managers. “Were they preparing for it, or were they playing the odds and then found themselves caught in a box?”

6 comments:

Papa Zu said...

Roger how can we assess how much of this year's storms and floods damage were natural and how much were poor flood control management? How does one consider the damage caused by the extra water run-off from farmers tiling their fields and preventing ground water absorption? How does one evaluate the amount of damage that could have been avoided if population growth in flood plains had been controlled?

Do we assess how much of the damage costs associated with these storms and floods are due to our own fault with landscape changes and dams?
How do we compare costs associated with storms/floods in "honest terms" between the past and the present if we've mucked things up with poor dam decisions, field tiling and overpopulation in high risk areas?

Harrywr2 said...

If a hydro operator is limited by various regional 'renewable energy mandates' as to how much water they can send thru the turbines(windmills have grid priority) and also limited by the endangered species act as to how much water they can spill over the top then their hands are effectively tied until after an emergency is declared.

Gerard Harbison said...

Papa Zu:

The upper Missouri basin has relatively little tillage, and very low population density.

Mark B. said...

After reading the article, I still don't know what to think. Is the ACE boxed in by competing demands? Seems entirely possible to me. It's not like Congress has never made conflicting requirements on agencies. Were piping plovers really made a priority this year?

gullygunyah said...

The whole wivenhoe issue is just an attempt by people not covered by insurance to lay blame somewhere in the hope of getting their flood prone properties repaired for nothing.
If you buy in an area that is known to flood, then suffer the consequences. But back to the point of the article. Yes the dam is delicately balanced to provide contradictory protection. However if you lived in Brisbane at the time just before the great deluge you would have heard people questioning the sense in dropping wivenhoe from close to 100 percent capacity to allow for further inflows.
If they had not taken these steps then things would have been even worse.
The dam operators did the best job they could have under the circumstances and mother nature just threw something bigger and badder than usual.
Having been here in '74. I saw the same type of flooding occur. It is a cyclical thing and we had just come out of a long drought.
I wonder if any judgement of the dam operators will take into account the fact that 2/3 of Queensland was under water. There were no dams to blame in any of these other areas.
It is a waste of taxpayers money to investigate the dam operators as they did what was possible and you can never be so arrogant as to think you can control nature.

Matt said...

Update to Wivenhoe: Looks like the engineers did NOT follow protocol.

The inquiry's finding that the manual was breached strips the owner and operator of the dam, the Queensland government and SEQWater, of legal indemnification and paves the way for claims for compensation.

...

The inquiry qualified its finding that "there was a failure to comply with the Wivenhoe manual" by observing that the flood engineers "were acting in the honest belief that the Wivenhoe manual did not" compel them to adopt a strategy based on forecast rainfall.

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