Visualization of Flow Alternatives, Lower Missouri River
U.S. Geological Survey Open-file Report OF02-122

Robert B. Jacobson and Jeanne Heuser, U.S. Geological Survey, Columbia, Missouri|
October 2001

 Direct Links to:

Scope

Methods

Alternatives

Frequency Hydrographs

Maximum-flow Hydrographs

Background

The U.S. Army Corps of Engineers (COE) "Missouri River Master Water Control Manual" (Master Manual) review has resulted in consideration of many flow alternatives for managing the water in the river (COE, 2001; 1998a). The purpose of this report is to present flow-management alternative model results in a way that can be easily visualized and understood. This report was updated in October 2001 to focus on the specific flow-management alternatives presented by the COE in the "Master Manual Revised Draft Environmental Impact Statement" (RDEIS; COE, 2001).  The original version (February 2000) is available by clicking here.

The COE, U.S. Fish and Wildlife Service (FWS), Missouri River states, and Missouri River basin tribes have been participating in discussions concerning water management of the Missouri River mainstem reservoir system (MRMRS), the Missouri River Bank Stabilization and Navigation Project, and the Kansas River reservoir system since 1986. These discussions include general input to the revision of the Master Manual as well as formal consultation under Section 7 of the Endangered Species Act. In 2000, the FWS issued a Biological Opinion that prescribed changes to reservoir management on the Missouri River that were believed to be necessary to preclude jeopardy to three endangered species, the pallid sturgeon, piping plover, and interior least tern (USFWS, 2000).

The combined Missouri River system is large and complex, including many reservoirs, control structures, and free-flowing reaches extending over a broad region. The ability to assess future impacts of altered management scenarios necessarily involves complex, computational models that attempt to integrate physical, chemical, biological, and economic effects. Graphical visualization of the model output is intended to improve understanding of the differences among flow-management alternatives. 

Scope

This report presents a visual, statistical presentation of five modeled flow-management alternatives and two reference alternatives for four selected sites on the Lower Missouri River at Sioux City, Iowa, Nebraska City, Nebraska, Kansas City, Missouri, and Boonville, Missouri (fig. 1). The flow-management alternative data have been generated by the COE using the Missouri River system Daily Routing Model (COE, 1998b). The Daily Routing Model calculates a water balance and routes water through six dams in the system, providing modeled outflows at 14 sites.

Flow-management alternatives presented in this report are limited to those under consideration in the August 2001 Master Manual RDEIS (COE, 2001) and two reference alternatives, the Current Water Control Plan (CWCP) and a run of river scenario (ROR), explained in "Modeled Alternatives."

Selection of MRMRS water-control rules is a complex and ongoing socio-economic and political process that attempts to balance desires of multiple stakeholders in the Missouri River basin. Flows modeled in each of the alternatives can be evaluated in terms of economic benefits and relative environmental effects; results of these effects models are presented elsewhere (COE, 1994-1999; COE, 1998a, RDEIS; COE, 2001.)  This report presents modeled streamflows to enhance visualization and understanding of proposed flow-management alternatives for the Master Manual; it does not attempt to evaluate relative performance, benefits, or environmental effects of alternatives.

Daily Routing Model

Results of flow-management alternatives have been modeled by the COE using the Daily Routing Model (COE, 1998b).  The modeled flows are synthesized from historical data on tributary inflows, calculations of streamflow depletions due to evapotranspiration and consumptive use of water, and modifications of outflows according to water-control rules that comprise a flow-management alternative. The model reproduces how reservoirs would be managed under a set of water control rules, given the actual range of variability of historical inflow data.  Historical data are available, or have been estimated, for the period 1898-1998. The Daily Routing Model uses these data and water-control rules to generate 100 years of daily flows for each of 14 sites for each flow-management alternative. The 14 sites consist of nine streamflow gaging stations on the Lower Missouri River and five streamflow gaging sites in inter-reservoir river segments. Model runs show the result of highly variable streamflow routed through the reservoir system according to water-control rules of varying complexity. Because storage in the Missouri River reservoir system is finite and because many tributary inflows are not regulated by reservoirs, the natural variability of the historical inputs is reflected in variability in the output discharge (fig. 2). Additional information on the Daily Routing Model can be found in COE (1998b).

 Methods

Modeled flow data for the alternatives were obtained from the COE. These files consist of dates and modeled flows at nine streamflow gaging stations on the Lower Missouri River. Of these nine sites, four were chosen to represent the range of effects on the Lower Missouri River (fig. 1). 

The data were reformatted and converted to watershed data management (WDM) format using the IOWDM program (Flynn and others, 1994; available at: http://water.usgs.gov/software/iowdm.html). The data were then analyzed for flow frequency using the program SWSTAT (Flynn and others, 1994; http://water.usgs.gov/software/swstat.html). The frequency hydrograph routine of SWSTAT calculates the relative frequency of flows for every day of the year for the period of record. Output from this program consists of flow exceedance percentiles (for example, 90^th percentile, 50^th percentile) and the corresponding flow for each day of the year.  The program was run to extract flows that were equaled or exceeded 90, 75, 25, and 10 percent of the time. 

The exceedance data were then plotted as shaded bands by day of the year to illustrate variations in flow during the year and over the 100 years of modeled record (fig. 3). Vertical variation in the graphs is a measure of variation among years and horizontal variation is a measure of seasonal variation. Overlays of reference alternatives present opportunities for visual comparisons.  Each of the new flow-management alternatives is compared to the run of river scenario (ROR - shown in light gray in graphs) and the 90^th and 10^th percentile flows of the Current Water Control Plan (CWCP - shown as black lines).

For comparison, full-service and minimum-service navigation flow targets (table 1) are shown for Sioux City, Nebraska City, and Kansas City graphs (COE, 1998b). Releases from Gavins Point dam to maintain navigation targets typically are higher than the target (for example, a 28.5 kcfs release compared to a 25 kcfs target for minimum navigation; 34.5 kcfs release compared to 31 kcfs target for full-service navigation).  Releases are higher than the targets to compensate for diminishing tributary inflows and to avoid having to increase flows during the tern and plover nesting season.  

The approximate discharge corresponding to the flood stage defined by the National Weather Service (NWS) flood stage also is indicated on each graph. The NWS flood stage is specific to the gage sites, and is highly dependent on the channel geometry as determined by levees and floodwalls. The NWS flood stage was converted to discharge by reference to U.S. Geological Survey stage-discharge rating curves for each gage.

A second set of four graphs was developed to show the effects of flow alternatives on the highest flows. These graphs present the maximum flows occurring for each day of the year over the 100 years of modeled flows. The ROR scenario and discharge at NWS flood stage are shown for comparison. 

Modeled Flow-Management Alternatives

The following flow-management alternatives are analyzed and presented here. Except for ROR, all the alternatives include drought conservation measures, reservoir unbalancing, and tern and plover mitigation rules (see COE, 1998a). The alternatives are identified by the codes shown in bold.  The Master Manual RDEIS (COE, 2001) emphasizes that the modeled Gavins Point (GP) management alternatives are meant to indicate a range of spring rise and summer low-flow conditions. The starting point for GP releases would be the GP1528, but the actual Gavins Point dam releases would be determined through an ongoing adaptive management process based on monitoring of biological responses.

Reference Alternatives:

·         ROR
The run of river alternative where streamflow is modeled for the conditions of constantly full reservoirs. Except for some evaporation from the reservoirs and the effects of small, triburary reservoirs,, it provides a realistic depiction of flows in the absence of regulation, that is, an estimate of  natural-river alternative.

·         CWCP
The Current Water Control Plan for the Missouri River Mainstem Reservoir System (MRMRS).

 

Management Alternatives:

 

·         MCP

Modified Conservation Plan where, during drought conditions, more water is conserved in upstream reservoirs by reducing navigation earlier in the season than in the CWCP.

 

The following four flow-alternatives evaluate the relative effects of high and low flow from Gavins Point (GP) dam. High flow is added to releases that are sufficient to meet  full-service navigation targets, nominally 34.5 kcfs (see Table 1). The spring rise is proposed to occur on an average of once very 3 years, as conditions allow. Low flows are achieved by subtracting 6 kcfs  (for GP1528, GP2028), or 13.5 and 9.5 kcfs (for GP1521 and GP2021) from full-service navigation releases.

 

·         GP1521

High: A 15 kcfs spring rise above full-service navigation releases.
Low: A split navigation season with two low-flow periods during the summer of 21 and 25 kcfs.

 

·         GP1528
High: A 15 kcfs spring rise above full-service navigation releases.

Low: A release of 28.5 kcfs (full-service navigation) throughout the navigation season.

 

·         GP2021
High: A 20 kcfs spring rise above full-service navigation releases.

Low: A split navigation season with two low-flow periods during the summer of 21 and 25 kcfs as proposed in GP1521.

 

·         GP2028

High: A 20 kcfs spring rise above full-service navigation releases.

Low: A release of 28.5 kcfs (full service navigation) throughout the navigation season.   

Results

The following hydrographs for the modeled reference and flow- management alternatives graphically show the differences among modeled flow-management alternatives for each site as well as showing the variable effects from upstream to downstream:

·        Frequency Hydrographs

·        Maximum-Flow Hydrographs

The frequency hydrographs show the seasonal and interannual variability of modeled flows that would be equaled or exceeded 10, 25, 75, and 90 percent of the time. The degree of change associated with the flow-management alternatives varies geographically, and is most pronounced at Sioux City, the station closest to Gavins Point dam. Downstream on the Lower Missouri River, additions of discharge from non-regulated or little-regulated tributary drainage basins modifies the effects of reservoir regulation. As a result, the modeled flow-management alternatives converge toward the Current Water Control Plan (CWCP) and exhibit greater seasonal variation for downstream stations.

The maximum-flow hydrographs show the seasonal variability of modeled maximum flows for each day of the year. These flows are those that are equaled or exceeded only one percent of the time on average. The discharges associated with NWS flood stage are specific to the gage sites, and are highly dependent on the channel geometry as determined by levees and floodwalls. The flow-management alternatives generally plot at lower discharges than the ROR alternative during the spring and at greater or equivalent discharges during August-November. The CWCP, MCP, and GP alternatives all plot nearly on top of one another; a few exceptions show 10-20 kcfs differences among the alternatives. In Sioux City the flow-management alternatives all plot substantially lower than the local flood stage discharge, with the exception of flows in June 1984. Moving downstream where flow is less regulated, maximum flows plot more frequently above flood-stage discharges.

References Cited

COE, 2001, Summary – Missouri River Revised Draft Environmental Impact Statement, Master Water Control Manual Review and Update: U.S. Army Corps of Engineers, Northwest Division, online publication August 2001, http://www.nwd-mr.usace.army.mil/mmanual/mast-man.htm.

COE, 1998a, Revised Draft Environmental Impact Statement: U.S. Army Corps of Engineers, Northwest Division Missouri River Region, Master Water Control Manual Missouri River Review and Update Study, v. 2A, 614 p.

COE, 1998b, Reservoir regulation studies – daily routing model studies: U.S. Army Corps of Engineers, Northwest Division Missouri River Region, Master Water Control Manual Missouri River Review and Update Study, v. 2A, 137 p.

COE, 1994-1999, Master Water Control Manual Missouri River Review and Update Study: U.S. Army Corps of Engineers, Northwest Division Missouri River Region, v. 1-13.

Flynn, Kathleen M., Hummel, Paul R., Lumb, Alan M., Kittle, John L., Jr., 1995, User's manual for ANNIE, version 2, a computer program for interactive hydrologic data management, WRI 95-4085, p. 211.

USFWS, 2000, Biological Opinion on the Operation of the Missouri River Main Stem Reservoir System, Operation and Maintenance of the Missouri River Bank Stabilization and Navigation Project, and Operation of the Kansas River Reservoir System: U.S. Fish and Wildlife Service, 286 p.

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