Management and Limnology Interact to Drive Water Temperature Patterns in a Middle Rockies River‐Reservoir System. (14th August 2019)

• Record Type: Journal Article
• Authors: McLaren, John S.; Royer, Todd V.; Van Kirk, Robert W.; Muradian, Melissa L.
• Is Part Of: Journal of the American Water Resources Association. Volume 55:Number 5(2019)
• Page Start: 1323
• Page End: 1334
• Publication Date: 2019-08-14
• Subjects: aquatic ecology -- water temperature -- outflows -- reservoirs -- river management -- large river ecology; Water-supply -- Periodicals; Hydrology -- Periodicals; Water resources development -- Periodicals; Water resources development -- Environmental aspects -- Periodicals; 333.9100973
• DOI: 10.1111/1752-1688.12782
• Languages: English
• ISSNs: 1093-474X

Abstract

Abstract: This study seeks to improve understanding of temperature patterns in reservoir outflows. We examined water temperatures in an irrigation storage reservoir, Island Park Reservoir, and its outflow, Henry's Fork of the Snake River in eastern Idaho. Our objectives were to (1) quantify the extent to which daily temperature ranges in the reservoir outflow deviated from other reaches of the Henry's Fork, and (2) test whether the reservoir's net volume change during the summer — expressed as the volume of water remaining in the reservoir on September 1 — predicted mean summer temperature in the outflow. Two years of temperature data showed dampened diel temperature cycles in the reservoir outflow. Model selection with 17 years of climatic, hydrologic, and reservoir management variables found mean summer temperature in the outflow was best predicted by September 1 reservoir volume and average summer air temperature. Two years of weekly reservoir thermal profiles indicated large changes in reservoir volume eliminated cool hypolimnetic water and encouraged mixing, allowing warm epilimnetic water to be discharged into the outflow. Increases in future drought frequency and severity and increases in summer air temperatures could increase the frequency of occurrence of high mean summertime water temperatures in the outflow. Our study provides important information for local managers by quantifying influences on outflow temperatures and the downstream river ecosystem. Abstract : Research Impact Statement: This study quantifies increase in outflow water temperature as a mid‐sized irrigation reservoir is drawn down, helping resource managers quantify costs and benefits of reservoir management strategies.