Here’s a post season spring runoff update from Deputy Public Works Director Greg Beckstrom:
This year has seen one of the heaviest, and the longest spring runoff periods in the last quarter century. Flows in the lower Provo River are now back below 1000 cfs (cubic feet/second) and Utah Lake has finally peaked. Following is a brief summary of the highlights.
IMPACTS: We have received no reports of any significant building damage due to surface flooding associated with spring runoff. Dozens of homes along the Provo River and/or near Utah Lake have had issues with intrusion of ground water into basements and crawl spaces which required pumping. Many acres of agricultural land have been inundated with water associated with the rising Utah Lake elevation and/or with high flows in the Provo River. Thousands of sand bags were distributed to property owners to minimize the risk of flooding damage along the Provo River and near Utah Lake.
UTAH LAKE: The Lake peaked in elevation last Wednesday (7/13) at 2.4′ above compromise, the highest it has been since 1986. The water surface has since started to recede an inch, or two. The lake elevation, combined with high flows in the Provo River, resulted in water flowing over the north bank of the River into the agricultural area west of the City limits. Those overflows ceased last week with the reduced flows in the River. The State Park operations have also been impacted with the high Lake elevation, although we are not aware of any permanent damage to facilities. There has been no impact to the facilities or operations at the Provo Airport, which is protected by dikes and pumps.
PROVO RIVER: The River peaked in flows at 1900 cfs on May 25th, the same magnitude as the peak flow experienced in 2005. In mid-June, after the low and mid elevation snow pack had largely melted and while large storage capacity still remained in the reservoirs, concern existed as to whether the remaining high elevation snow pack would be sufficient to fill the reservoirs; and flows in the lower Provo River were reduced to about 500 cfs. When the higher temperatures came in late June, the runoff in the upper Provo River exceeded expectations (over 3000 cfs, June 24th – 26th). Releases out of the reservoirs were increased to avoid uncontrolled overflows. Flows in the lower Provo River were between 1500 and 1800 cfs from June 24th to July 7th. Flows of this magnitude this late in the season are extremely rare. Current flows in the lower River are still over 600 cfs.
FRONTAL CANYONS: Peak flows out of the frontal canyons (Little Rock, Rock and Slate) were lower than expected, due to the extended cool temperatures this spring. However, like flows in the Provo River, moderate steady flows occurred much later and longer than during other high runoff years. It is rare for flows out of Rock Canyon to be flowing through the basin park on the 4th of July (over 20 cfs this year). It would be unprecedented for that to occur on Pioneer Day. Rock Canyon sustained flows above 15 cfs for two months (May 15th to July 13th), peaked at 40 cfs on June 17th, and are still above 5 cfs.
Looking Ahead: Maintenance work remains to be done, particularly as flows are reduced along the Provo River, to remove debris and to clean storm drain outlets into the River. With normal weather patterns, the elevation of Utah Lake should return to compromise level this year. However, cool and wet weather this summer and fall, followed by another winter of heavy snow pack; could result in next spring’s runoff season starting with the Lake elevation already above compromise.
Let me know; if you have any questions about this year’s runoff season, or if you have any thoughts about things that could be improved, particularly regarding the information that is included in the regular updates.
Thanks again to all those who have worked to make this year’s runoff season more manageable.