Note: This document is the draft minutes of the Water Management Committee meeting and is subject to change. The official meeting minutes may be different if corrections are made by the Water Management Committee before final approval.

The Water Management Committee (WMC) meeting began at 9:30 a.m. at the Crystal Inn, Denver, Colorado. The agenda was reviewed and the priority agenda item was identified as the Discussion of North Platte Channel Capacity Issue / Preparation for the February 18 workshop with the Governance Committee. The WMC also decided not to break for lunch. Draft minutes of the March 28, 2002; May 10, 2002; August 27, 2002; September 16, 2002; and October 17, 2002, meetings were approved. The March 28, 2002; August 27, 2002; and October 17, 2002, minutes were approved with corrections.

Gray Lewis of Parsons reviewed with the WMC the report entitled, Preliminary Evaluation of Channel Capacity in the North Platte River at North Platte, Nebraska, that was prepared for the Central Nebraska Public Power and Irrigation District (Central). The evaluation included 1) preliminary assessment of alleged channel changes, 2) preliminary assessment of causes of the alleged changes, 3) preliminary assessment of data collection or analyses needs, and 4) preliminary assessment of potential remediation actions. Gary defined the terms "channel capacity" and "carrying capacity" used in the report as follows.

• Channel Capacity – flow rate when water is just about to escape over the top of the banks of the main unvegetated conveyances in the river, also referred to as the effective discharge.


• Carrying Capacity – flow rate when water is beginning to restrict access to developed properties in the floodplain, also referred to as the flood stage discharge rate.

Based on review of existing gauge records, relevant existing studies, aerial photos, and personal contacts the report confirms that the carrying capacity in the North Platte River at North Platte, Nebraska, has been reduced. Potential causes of the reduction include 1) the growth of Phragmites (reed weed) and purple loosestrife, which increase overbank flow resistance; 2) blockage of overbank flow chutes by vegetation, beaver dams, and rock crossings; 3) blockage of downstream drainage flow paths; 4) artificial drain created by the State no longer functioning; 5) large transient sand bars (macroforms) in the main channel. It was noted that the channel capacity range of 1,700 to 2,000 cubic feet per second (cfs) established in a Corps of Engineers' 1989 study is consistent with observed flows leaving the main channel of the river in 2002 and the channel capacity has not changed significantly over that time period. Changes occurring in the floodplain are believed to be resulting in the increased flow depths. Gary noted that he was unable to confirm whether the National Weather Service (NWS) action to reduce the flood stage to 5.7 feet (1,980 cfs) relied on information other than information provided by one land owner.

Tim Randle of the Bureau of Reclamation presented graphs of stage-discharge trends for the river gauge at North Platte , Nebraska. The graphs show that channel conveyance capacity of the river began declining in 1952, and flood flows in 1971 restored the conveyance capacity up to a flow of at least 2,000 cfs and flood flows in 1983 partially restored the conveyance capacity. The WMC discussed the cyclical trend evident in the data for the period 1960 through the late 1980s where the gauge heights increased and then declined when two high flows occurred. The last decade again shows an upward trend.

The Fish and Wildlife Service (FWS) identified the channel capacity issue relates to the Program in two areas: 1) the ability of the Program to deliver up to 5,000 cfs of Program water to provide a three day pulse approaching but not exceeding bank full capacity at Overton and 2) meet summer target flows in the habitat. Improved carrying capacity at North Platte reduces the size of potential off stream storage that may be needed to meet the three day pulse and improves ability to make Environmental Account (EA) releases to provide summer target flows, during period of critical need when EA releases and downstream irrigation demands may need to share river capacity. The FWS has expressed the need to maintain an EA release capability of about 900 cfs in the channel at North Platte for summer target flows during period of critical need.

Following considerable discussion regarding the channel restriction issue, the WMC developed a list of potential alternatives for consideration by the Governance Committee at their February 18, 2003, workshop. It is anticipated that the establishment of a process to address the Program water delivery issue will allow the Program to move forward. The alternatives below are presented in no particular order.

• Protect properties (flood proof by means of berms).
• Divert water from properties (restore north diversion channel)
• Manage/eliminate vegetation/overbank obstructions (Phragmites, beaver dams, etc.)
• Restore downstream outlet
• Create berms in main river channel to increase flow velocity and mobilize bed
• Dredging
• Buyout property owners in flood plain