February 2001

The U.S. Army Corps of Engineers (COE), U.S. Fish and Wildlife Service (FWS), Missouri River states, and Missouri River basin tribes have been participating in discussions about alternative management of the Missouri River mainstem reservoir system (MRMRS), the Missouri River Bank Stabilization and Navigation Project (BSNP), and the Kansas River reservoir system (KRRS) since 1986. These discussions include general input to the revision of the Missouri River Main Stem Reservoir System Reservoir Regulation Manual (Master Manual) as well as formal consultation under Section 7 of the Endangered Species Act.

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. Understanding of the relative differences among management alternatives requires visualization of large output datasets.

This report presents a visual, statistical analysis of six modeled flow alternatives and two reference alternatives, for four selected sites on the Lower Missouri River (fig. 1). The flow-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. This report is concerned only with sites representative of the Lower Missouri River at Sioux City, Iowa, Nebraska City, Nebraska, Kansas City, Missouri, and Boonville, Missouri.

Water-control alternatives presented in this report are limited to those active under consideration in early 2001, and two reference alternatives, the current water-control plan (CWCP) and a run-of-the-river scenario (EVQ2). The alternatives will be discussed in more detail in the following section. Evaluation of alternatives is an ongoing process; additional alternatives will be analyzed and added to this report as they are proposed and modeled.

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. Streamflows 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; http://www.nwd-mr.usace.army.mil/mmanual/mast-man.htm). This report does not attempt to evaluate relative performance, benefits, or environmental effects of alternatives. The intent is simply to present modeled streamflows to enhance visualization and understanding. 

Results of flow alternatives have been modeled by the U.S. Army Corps of Engineers 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 rule scenarios.  In this way, 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 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 inflow 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

Discharge 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 (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 duration hydrograph routine of SWSTAT calculates cumulative flow frequency for every day of the year for the period of record. Output from this program consists of flow exceedence 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. These 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). Overlays of reference alternative present opportunities for visual comparisons.  Each of the new alternatives is compared to the run-of-the-river scenario (shown in light gray) and the 90^th and 10^th percentile flows of the current water control plan (shown as black lines).

The following alternatives are analyzed and presented here. Except for EVQ2, 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:

· EVQ2.  The run-of-the-river alternative where streamflow is modeled for the conditions of constantly full reservoirs. Except for some evaporation from the reservoirs, it provides a realistic depiction of flows in the absence of regulation, that is, a natural-river alternative.

· CWCP.  The current water-control plan for the MRMRS.

Management Alternatives:

· FW22. Prescribed by the USFWS in the Missouri River Biological Opinion (USFWS, 2000), this alternative includes a 17,500 cubic feet per second (17.5 kcfs) spring rise above full-service navigation releases from Gavins Point dam, when conditions permit (to be achieved on average once every three years), and a split navigation season with two low-flow periods during the summer of 21 and 25 kcfs.

· FW32. This alternative was run to evaluate the relative effects of a 30 kcfs spring rise above full-service navigation releases from Gavins Point dam (to be achieved on average once every three years), and the split navigation season as specified in FW22.

· FWMS00. This alternative was formulated to evaluate the effects of a 17.5 kcfs spring rise (to be achieved on average once every three years) coupled with release of 28.5 kcfs at Gavins Point throughout the navigation season.

· FWMS16. This alternative is identical to FWMS00 but includes the effects of 1.6 million acre feet (MAF) depletion from the basin.

· MODC00. This alternative is similar to CWCP but delays fall evacuation of the reservoirs (when possible) until after September 15 at Kansas City.

For comparison, full-service and minimum-service navigation flow targets (table 1) are shown on graphs of results for Sioux City, Nebraska City, and Kansas City; navigation targets are not defined for Boonville (COE, 1998b).

References Cited

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.