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Missouri River Water Management


Frequently Asked Questions about the Missouri River System

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 The following questions were asked during public teleconference calls held from April 20-23, 2020  
 Following the 2019 flooding, will the Corps “re-think” rather than just “re-build” portions of the levee system that repeatedly fail? We also request a thorough examination of the levee system be conducted and that all levees are regularly inspected for compliance to current federal levee regulations. 

The Corps is using a three phase recovery approach to ensure we address the full scope of the issue:

  • Phase I: initial response and critical breach closures. This phase is nearing completion.
  • Phase II:  includes repair of levees to original design. Phase II began last summer and is not expected to be complete before 2021.
  • Phase III: includes a review of long-term flood risk reduction, which includes 1) pursuing a small-scale study using the Planning Assistance to States (PAS) program, 2) an updated flow frequency analysis, and 3) a multi-year General Investigations study through Section 216 of the Flood Control Act of 1970.

Phase III of the recovery approach includes a multi-state study that would look at a variety of measures to address flood risk. The multi-year General Investigations study effort will include a 4-state partnership between USACE and the states of NE, IA, KS and MO.  The multi-year study will formulate and evaluate measures for reducing flood risk, damages, and vulnerability, and improving infrastructure resilience. The study’s intent is to develop a comprehensive set of measures and a plan to reduce risk, enhance resiliency and to reduce the costs of repeated repairs of the levee system.

Levee setbacks and river widening may be measures considered as part of that study. Once the study kicks off, it will include a scoping process that will allow for public input into the measures and alternatives to be considered.

USACE regularly inspects levees within its Levee Safety Program to monitor their overall condition, identify deficiencies, verify that needed maintenance is taking place, determine eligibility for federal rehabilitation assistance (in accordance with P.L. 84-99), and provide information about the levees on which the public relies.  Inspections also provide information on continuous risk management activities and serve as a primary source of information related to levee condition and performance for risk assessments.

 Will the Corps look at additional ways to implement flood control methods, such as levee setbacks and/or river widening projects? We believe this type of flood reduction efforts will lower crests during high flow events and give the river the room it demands during these frequent high water periods.

Phase III of the recovery approach includes a multi-state study that will look at a variety of measures to address flood risk. Levee setbacks and river widening may be measures considered as part of that study. Once the study kicks off, it will include a scoping process that will allow for public input into the measures and alternatives to be considered.

  1. Can you provide an update on the establishment of the soil moisture network in the basin as authorized in recent Water Resource Development Acts?
  2. Has the Corps requested all the funding needed to install, operate, and maintain this much needed network?
  1. USACE is taking steps to implement the network. There are five states in the Upper Missouri River Basin the network is focusing on:  Montana, Wyoming, North Dakota, South Dakota and part of Nebraska. Each state has a mesonet, which is a state-operated network of soil moisture probes and hydrometeorological instruments. We are working with the universities in those five states that operate the mesonets to upgrade their capabilities to provide consistent data across the basin, which will include the instrumentation for plains snow. The data will be used by a number of agencies to improve existing products and develop new ones, and also used by the water management office for reservoir management operations.

    In 2018 we funded an initial instrumentation study with South Dakota State University to identify the recommended instruments needed to collect the data. Recently we awarded initial proof-of-concept contracts with states of Montana, Wyoming and South Dakota to upgrade one of the existing sites in each of those three states and identify lessons learned for wider implementation. We are continuing to develop contract capabilities with the state universities to upgrade the rest of their sites so they can provide consistent data. In the next year we will also be identifying the overall approach for installing new sites across the upper basin.
  2. The total project cost is estimated to be $43 million and Congress has so far appropriated $2.6 million. The Corps continues to express the capability each year and we rely on funding appropriated by Congress for project execution. Breaking that out year by year, that $2.6 million. $100k was in Fiscal Year2018, $1.5 million in FY2019, and $1 million in FY2020. The Corps has limited capacity to fund operations and maintenance after the sites are installed.  This really depends on type of funding appropriated by Congress. We are working with the states and other agencies to determine how long-term operation and maintenance will be funded once installation is complete.
  1. Sedimentation in the reservoirs continues to be a big concern for the League and many other groups. How is the Corps working with federal, state, and tribal agencies and landowners to implement practices that will reduce erosion from entering the system?
  2. Can you provide any updates on exploring methods to reduce the amount of accumulated sediment currently in the reservoirs?
  1. In general, sediment management in the watershed is not the responsibility of USACE. The Corps lacks authority to implement projects in the watershed. However, the Corps has done some studies in the Niobrara river basin through our regional sediment management program where we identified a number of possible sources and identified at the conceptual level some possible solutions that could be implemented if authority and funding was provided.
  2. There are multiple reservoir flushing events across the US being monitored by the Corps. We are currently developing better tools to develop sediment yield from the reservoirs where data is sparse. USACE is updating the regulatory guidance on permitting discharging sediments from reservoirs and incorporating this into lessons learned. We are looking at efforts in reservoir sediment research to develop tools that can be used.

    Multiple districts including the Omaha District have begun working on Sediment management plans for reservoirs to examine ways to reduce sediment load from the watershed as well as ways to regain equilibrium of sediment transport in the channel below the dams. These efforts are in their infancy, and in these two efforts in particular, action is still quite a ways into the future.
 What is the volume that the upstream dams could hold before you had mandatory releases from Gavins Point?

It is unclear what is meant by mandatory releases as we are required to release water from all the projects every day to meet the Congressionally authorized purposes. However, with respect to flood control operations, there are two separate zones -- the annual flood control and multiple use zone and the exclusive flood control zone. Ideally we would operate in the annual flood control and multiple use zone year-round. While in this zone, we could capture the spring and early summer runoff that could cause or contribute to flooding and meter that water out at the lowest possible rate over the longest period of time. This provides the greatest amount of flood risk reduction.

The top of the annual flood control and multiple use zone is set at 67.7 million acre feet (MAF).  Once System storage exceeds this mark we are in the exclusive flood control zone, which we attempt to empty as quickly as practicable. It is important to keep in mind that any water stored in these flood control zones must be evacuated before the next runoff season.

 What is the flow frequency of the flood of 2019? For example, was it an 80- or 100-year event?

The flow frequency has not been determined.

 What was the percentage of the federal dams Pick/Sloan and/or federal levees that overtopped in the Omaha District?

No federal dams were overtopped in 2019.  Several levees in the Omaha District were overtopped.  On the left bank of the Missouri River, starting at L611-614, all levees were overtopped. On the right bank, all levees on the Platte River overtopped. Downstream of the Platte/Missouri River confluence on the Missouri River right bank, no levees were overtopped. The failure of the left bank levees took the pressure off the right bank levees.

 What is the design level recurrence interval for Pick/Sloan and/or federal levees upstream from Kansas City, Missouri?

Only the federal levees that protect cities (e.g. Omaha) were designed for recurrence interval and that level is generally 500-year.The remainder of the levees are referred to as agricultural levees and were designed to a certain discharge (flow rate); they were not designed for a certain level of protection. The design discharge varied depending on location.

 What was the peak recurrence interval for the flood of 2019 at the Missouri River streamgaging locations at St. Joseph, Waverly and Hermann?

Those recurrence intervals have not yet been determined.

 What is the design recurrence interval for Pick/Sloan and/or Federal levees downstream from Kansas City, Missouri?

Only the federal levees that protect cities (e.g. New Haven) were designed for recurrence interval and that level is generally 500-year.  The remainder of the levees are referred to as agricultural levees and were designed to a certain discharge (flow rate); they were not designed for a certain level of protection.  The design discharge varied depending on location.

 In 2019, what percentage of the Pick/Sloan and/or Federal levees that over topped in the Kansas City District?

Approximately 4.25% of the Federal Levee systems in the Kansas City District overtopped in 2019. That percentage represents 2 of 47 [R500 (KS) and L246 (MO)]. Nine (9) Federal levees overtopped in the 1993 flood event, 4 suffered subsequent breach development [L400 (MO), R471-460 (KS), L246 (MO), and Lower Chariton (MO)] (only 46 Fed systems in 1993, percentage overtopped was 19.6%)

 At Oahe, the April 21 reservoir elevation is 1610 feet. 1607.5 feet is the base of the flood control pool. It looks like you’ll go back down to 1609 feet. Are you headed back to 1607.5 feet?  What is your plan for reservoir pool elevations at Oahe for 2020?

We typically store runoff in Oahe during this time of year. During the summer and fall we will evacuate the stored water from Oahe’s annual flood control and multiple use zone. Our April 1 reservoir studies shows that the Oahe reservoir will have a peak elevation of 1615 feet, which is 2 feet below the base of the exclusive flood control zone.  Those reservoir studies indicated that the Oahe reservoir elevation would be about 1612 feet at the end of April.  It’s been a little drier than expected this month so it appears that the end-of-April pool elevation will be a little lower than forecast.

 Has an after-action-review of water management actions from the 2019 flood been completed?  If so, will it be released to the public?

We are just now wrapping up the final edits to the Summary of Operations report for 2019.  When it is completed, hopefully in the next couple weeks, it will be posted to our public website.

 Will system storage be drawn down to the bottom of the annual flood control and multiple use zone levels in all system reservoirs?  Does USACE have plans to draw the system down below the base of the annual flood control and multiple use zone (56.1 MAF)?  CPMR is concerned about any efforts to draw down below this level, due to impacts on navigation and other water supply needs.  We recall how the 2011 flood was followed by the 2012 drought, and USACE should be mindful of unintended impacts of overly aggressive releases.

Under all of our runoff scenarios, (upper basic, basic, and lower basic,) our reservoir studies indicate that the System storage will be 56.1 MAF, at the base of the annual flood control and multiple use zone, at the start of the 2021 runoff season.  Our goal is that all reservoirs are “balanced” and each at their respective bases of annual flood control and multiple use, but that is not always possible.  Some may be above a little and some may be a little below. At this time we have no intention of overdrafting the reservoir system.

 How will USACE incorporate suggestions on flood recovery from the lower river working group of states?

The lower working group is one of many efforts that are aimed at flood recovery including an after action review, regular coordination with basin stakeholders, studies related to Phase 3 and other efforts to improve flood recovery and resiliency.

 The Pick Sloan levees were designed based on discharge. The Data flow frequency from 2004, is that how the flow frequencies will be decided for the federal levees?

The levees, except for ones in larger cities such as Omaha and Kansas City, were not designed to a given level of protection. There is not a flow frequency assigned to the levee design. It varies from levee to levee as to the protection level.  The non-federal levees are generally built below the 100-year level of protection. The overarching (Phase III) study has not begun yet.  Updating the flow frequencies will be part of that study.

 Levee construction and reconstruction planning and redesigning – does the water storage capacity loss due to sedimentation get taken into account when redesigning levees?

It isn’t a factor. The districts are updating the Missouri River flow frequency analysis from Sioux City to the mouth but the flood control storage space doesn’t change. As the reservoir sediment accumulates, the annual carryover storage is reduced.  Flood control storage remains at 16.3 MAF.

 Gavins Point – flood control is not a large factor in the Gavins Point reservoir. How does the operation of Gavins Point factor in? What is its role?

Gavins Point is a re-regulation reservoir with a very small amount of flood control storage, which is to be used only for small, local events.  Gavins Point smooths out releases from upstream Fort Randall, which has large release fluctuations based on hydropower demands.

 Does the sediment affect the re-regulation aspect of Gavins Point Dam?


The sediment doesn’t currently affect the re-regulation, but it does affect access in the Gavins Point headwaters and the water levels in the Niobrara area.

 The following questions are among those asked most frequently.

 Can you add river stations to the bulletins on your website?

Yes. We’ve recently modified our Daily River Bulletin to include additional river stations.

We also link to hourly data for several stations. 

 Will the Corps be updating any of their technical reports, such as Runoff for Annual Operating Plan Studies that takes into account 2018 and 2019 runoff?

Technical studies are periodically updated to include the most recent information. The report “Runoff Volumes for AOP Studies” was last updated in August 2013 to include runoff data from 1898 to 2011. The Corps will complete a preliminary analysis of the runoff data to see if an update of the report is needed before the draft AOP is prepared in August 2020.

A variety of studies and reports on the operation of the Missouri River Mainstem System are prepared and published regularly.

Statistical information on the operation of the Missouri River Mainstem System is recorded and evaluated by the Missouri River Water Management Division.

 Where are the pinch points in lower Missouri River -- what is the non-damaging conveyance at each Missouri River streamgaging location from Gavins Point Dam to Hermann, Missouri?
Missouri River Location Flood Stage (in feet) Flow at Flood Stage (in cfs)
Sioux City 30.0 125,000
Decatur 35.0 121,000
Omaha 29.0 116,000
Nebraska City 18.0 92,000
Rulo 17.0 90,000
St. Joseph 17.0 100,000
Kansas City 32.0 241,000
Waverly 20.0 117,000
Boonville 21.0 162,000
Hermann 21.0 195,000
 Which agency is responsible for making runoff inflow projections?

The U.S. Army Corps of Engineers (Corps) Missouri River Basin Water Management (MRBWM) office develops runoff volume forecasts for the purpose of meeting downstream flow targets to serve system purposes such as navigation, water supply and flood control.

Runoff forecasts for Mainstem System operations use data from the National Weather Service’s Missouri Basin River Forecast Center and Climate Prediction Center, the U.S. Geological Survey, the Natural Resources Conservation Service, State climate offices, and others.

Short-Range Runoff (Inflow) Projections: Day-to-day scheduling of releases is necessary to regulate the System on an integrated basis and requires the Corps to develop daily flow forecasts at key streamgaging locations throughout the basin. These forecasts are based on observed and anticipated precipitation, temperature, temperature-snowmelt relationships, rainfall-runoff relationships, observed streamflow in the main stem of the Missouri River and tributaries, previous precipitation and other factors that often may be subject to only qualitative analysis.

Lower Missouri River Streamflow Forecasting: Scheduling releases from Gavins Point during the open-water season (generally late March through mid-December) is based on downstream navigation target locations on the Missouri River at: Sioux City, IA; Omaha, NE; Nebraska City, NE; and Kansas City, MO. Of these four locations, Omaha, Nebraska City and Kansas City also serve as downstream flood control target locations. The Corps’ Missouri River Basin Water Management office schedules the mainstem project releases, including Gavins Point. Scheduling Gavins Point releases requires developing accurate forecasts of lower Missouri River reach inflows between Gavins Point, the lowermost System dam, and flow forecasts of at the four downstream target locations. These forecasts are developed daily and project 14 days in the future. They are compared to daily forecasts developed by the NWS's Missouri Basin River Forecast Center.

Monthly Reach Inflow (Runoff) Forecasts: The first week of each month, the MRBWM office prepares a monthly incremental inflow forecast for the six System reservoir reaches. These forecasts are based on, but not limited to: monthly average reach runoff, historical reach runoff, existing and previous soil moisture conditions, reach precipitation and/or river gage readings during March-April and May-July, observed reach temperature, accumulated snow over the incremental drainage area, long-term precipitation and temperature outlooks, and accumulated mountain snow water equivalent. Projected runoff calculations includes water in the system, in the soil, in mountain snow, and plains snow estimates and precipitation outlooks from the National Weather Service's Climate Prediction Center.

 Why does the runoff forecast change so much in some years?

Short-term forecast precipitation is not included in runoff volume forecasts. When and where precipitation occurs and how it appears in tributaries is imprecise. Forecasting runoff volume without including forecast precipitation is why runoff volume estimates can change significantly.

 What is current stage and flow in my location?

The National Weather Service Missouri River Basin Forecast Center provides forecasts for rivers and tributaries in the Missouri River Basin.

The Daily River Bulletin is a daily product from the U.S. Army Corps of Engineers Missouri River Basin Water Management office, which includes current stages and flows for various locations throughout the basin.

 What are you going to be releasing in the next few months?

Each month we update our upper basin runoff forecast and reservoir studies. The Missouri River Mainstem System of dams is operated as a system and release decisions are evaluated system-wide.

 Are there flood forecasts, similar to Hurricane Season predictions?

Yes, the National Weather Service regularly issues Hydrologic Outlooks. They also share considerable information regarding Flood Safety on their website.

There are two types:
Short-term (1 to 7 days) Hydrologic Outlooks can be issued to alert the public of the potential for flooding in the near-term such as when heavy rainfall is forecast that could result in flooding or aggravate an existing flood if it occurs.

Long-term (weeks to months) Hydrologic Outlooks may also provide river or reservoir level and/or flow information. This information could be used for water supply concerns or projection of snowmelt flooding. In the Missouri Basin, the Spring Hydrologic Outlook is issued in February and March.

A long-range river flood outlook is available on the NWS website and shows locations with a greater than 50% chance of exceeding river flood levels in the next 3 months. The website is interactive and can show flood chance percentages from 5 to 95%.

Hazardous Weather Outlooks and Alerts may also be indicators of potential for flash flooding.

Similarly, drought information is also available for Weekly, Monthly or Seasonal Outlooks.

 Why don't you release more water in the winter months?

The Missouri River freezes completely over in the upper basin during the winter, which greatly restricts the amount of water we can release from the Fort Peck, Garrison and Oahe reservoirs. While it appears it would be beneficial to make higher releases during the winter, it is not that simple. During the winter an ice cover forms over the river channel making the river a “pipe”. If we push too much water down the “pipe”, it will burst. When the ice cover forms, the river stage dramatically increases. Once the ice cover forms, we slowly increase releases and smooth out the underside of the “pipe”; thus releasing more water. However, the maximum winter releases are never going to be as high as the releases we can make during open water (non-ice cover) conditions.

 Wouldn’t higher releases prevent river ice from forming?

Increasing flows on the river does not prevent ice from forming. Reasons for this include sustained outside temperatures below freezing, high wind chills, and water temperatures that will drop below freezing at the water’s surface.

Increasing flows also increases the river stage. The river will still freeze but at a higher stage, which would increase flood risk.

A warmer winter, even in Montana and North Dakota, still means below-freezing temperatures and frozen tributaries and rivers.

 What does flood storage capacity mean and why can’t it be bigger?

Space is reserved in each reservoir to capture and manage runoff during the high runoff months (March-July) which is then emptied during the lower runoff months (August-November). That reserved space is the designated flood storage volume. A volume of 16.3 million acre-feet (MAF) was established based on more than 100 years of hydrometeorogical data and the engineering capacity of the System projects.

The Missouri River Basin Water Management office makes regulation decisions so all 16.3 MAF of the reserved flood control space is available at the start of each runoff season, which is around March 1. The combined flood control space of the six projects totals 16.3 MAF. When we have 16.3 MAF of flood control space available to capture runoff, we are also storing 56.1 MAF of water in the six reservoirs.

If the 16.3 MAF of flood control space were larger, then the releases would be even lower when runoff is lower and releases would be even higher when runoff is higher. This is because the System would still be operated to return to the set amount of available flood control space by March 1.

 Who do we contact when the river is flooding?

There are different resources available to you when the river is flooding dependent upon your location.

Local levee sponsors should be contacted regarding interior drainage issues, or water on the "dry side" of the levee. The National Levee Database is the best resource for locating your local levee sponsor.

If you want to take measures to prevent stream bank erosion during a high water event, work with local Regulatory offices to ensure you are in compliance with state and federal laws.

If you represent a Federal, Tribal, State or Local agency you can contact either the Kansas City District Emergency Management Office (for Missouri Basin locations south of Rulo, NE) or the Omaha District Emergency Management Office (for Missouri Basin locations north of Rulo, NE).

 What locations are above flood stage today?

The National Weather Service Missouri River Basin Forecast Center shows locations that are currently in minor flood stage or higher.

This NWS MRBFC chart shows river stage observations for locations throughout the Missouri River Basin.

 What do we need to know about El Nino and La Nina?

The National Oceanic and Atmospheric Administration monitors the status of El Nino and La Nina providing outlooks each quarter.

Quarterly climate outlooks are published through the National Integrated Drought Information System.

The National Weather Service Climate Prediction Service has compiled several frequently asked questions about El Nino and La Nina.

 How do Spillway Gates hold back water without leaking?

Each gate has rubber seals around them. There will still typically be some leakage. There are stoplogs that can be placed on the upstream side of the gate that will allow work, such as inspecting or replacing the rubber seal, on a dewatered gate to take place when water is above the spillway elevation.