Background

The Central Utah Water Conservancy District (District) the Utah Reclamation Mitigation and Conservation Commission (Mitigation Commission), and the United States Department of the Interior, Central Utah Project Completion Act Office (CUCPA Office), as Joint Lead Agencies (JLAs), have determined that the winter instream flows for Diamond Fork River can no longer be delivered from the Sixth Water Flow Control Structure. In addition, the JLAs will be initiating studies over the course of several years on the Diamond Fork River and Sixth Water Creek systems to determine the desired flow regimes. The JLAs are soliciting input from the public, interested parties, and agencies regarding the proposed recommendations (described in more detail later).

Minimum Instream Flows

The minimum instream flows for Sixth Water Creek are delivered through the Strawberry Tunnel. Since the completion of the Sixth Water Flow Control Structure, the Diamond Fork River minimum instream flows have been delivered through the Sixth Water Flow Control Structure's sleeve valves (Note: minimum flows are achieved through a combination of natural and supplemental flows).

Title III, Section 303(c)(1) of CUCPA (Public Law 102-575) legislates minimum instream flows for Diamond Fork River and Sixth Water Creek.

Minimum winter and summer instream flows
(all values cubic-feet per second)
Winter Flows Summer Flows
Diamond Fork
near Monks Hollow
60 cfs
October - April
80 cfs
May - September
Sixth Water
at Strawberry Tunnel
25 cfs
November - April
32 cfs
May - October

Sixth WaterFlow Control

Sleeve Valves Issues at the Sixth Water Flow Control Structure

The release of winter flows for Diamond Fork River through the Sixth Water Flow Control Structure has resulted in damage to the sleeve valves. The damage includes 'pitting' on the valve body and erosion of the valve seats. If left unchecked this would've caused the valves to fail. In fall of 2012, the District and CUPCA Office redesigned and repaired the sleeve valves in hopes that they would better handle the extreme range of flow deliveries at the Sixth Water Flow Control Structure. However, the newly redesigned and reconstructed sleeve valves have the same problems as mentioned. Therefore, the JLAs will no longer be able to deliver the Diamond Fork River winter minimum instream flows at the Sixth Water Flow Control Structure. The Sixth Water Creek and Diamond Fork River winter minimum flows will be made through the Strawberry Tunnel. This means that minimum instream flow targets for Diamond Fork would need to be satisfied from the outlet of the Strawberry Tunnel and all the way down Sixth Water Creek. The JLAs are concerned that higher flow rates may cause adverse impacts to ecological conditions of Sixth Water Creek.

Sixth WaterSleeve Valves

Project Map