Assessing the potential of reservoir outflow management to reduce sedimentation using continuous turbidity monitoring and reservoir modelling

Abstract

In‐stream sensors are increasingly deployed as part of ambient water quality‐monitoring networks. Temporally dense data from these networks can be used to better understand the transport of constituents through streams, lakes or reservoirs. Data from existing, continuously recording in‐stream flow and water quality monitoring stations were coupled with the two‐dimensional hydrodynamic CE‐QUAL‐W2 model to assess the potential of altered reservoir outflow management to reduce sediment trapping in John Redmond Reservoir, located in east‐central Kansas. Monitoring stations upstream and downstream from the reservoir were used to estimate 5.6 million metric tons of sediment transported to John Redmond Reservoir from 2007 through 2010, 88% of which was trapped within the reservoir. The two‐dimensional model was used to estimate the residence time of 55 equal‐volume releases from the reservoir; sediment trapping for these releases varied from 48% to 97%. Smaller trapping efficiencies were observed when the reservoir was maintained near the normal operating capacity (relative to higher flood pool levels) and when average residence times were relatively short. An idealized, alternative outflow management scenario was constructed, which minimized reservoir elevations and the length of time water was in the reservoir, while continuing to meet downstream flood control end points identified in the reservoir water control manual. The alternative scenario is projected to reduce sediment trapping in the reservoir by approximately 3%, preventing approximately 45 000 metric tons of sediment from being deposited within the reservoir annually. This article presents an approach to quantify the potential of reservoir management using existing in‐stream data; actual management decisions need to consider the effects on other reservoir benefits, such as downstream flood control and aquatic life. Copyright © 2012 John Wiley & Sons, Ltd.

Sustainable sediment management in reservoirs and regulated rivers: Experiences from five continents

“…Analysis of historical operations during 48 flood events plus modeling showed that a measurable increase in sediment throughput could be achieved by making relatively minor changes to the operating rule, while still maintaining downstream flood control targets [ Lee and Foster , ]. Compared to the conventional reservoir operation, “the altered scenario purposefully minimized reservoir elevation and residence time through larger, more rapid releases of water after periods of high inflows,” resulting in measurably decreased trap efficiency [ Lee and Foster , :1437]. This reduction in sediment trapping efficiency is achieved without any structural modifications, by simply including a sediment management objective in the reservoir operating rule.…”

“…1002/2013EF000184 2013. Compared to the conventional reservoir operation, "the altered scenario purposefully minimized reservoir elevation and residence time through larger, more rapid releases of water after periods of high inflows," resulting in measurably decreased trap efficiency [Lee andFoster, 2013:1437]. This reduction in sediment trapping efficiency is achieved without any structural modifications, by simply including a sediment management objective in the reservoir operating rule.…”

Modeling density currents in a typical tributary of the Three Gorges Reservoir, China

“…As the model assumes lateral homogeneity, it is best suited for relatively long and narrow waterbodies exhibiting longitudinal and vertical water quality gradients. This model has been successfully applied to stratified water systems, including lakes, reservoirs, and estuaries (Afshar et al, 2013;Berger and Wells, 2008;Bowen and Hieronymus, 2003;Choi et al, 2007;Kuo et al, 2006;Lee and Foster, 2013;Park et al, 2014;Wells et al, 2012). The CE-QUAL-W2 model was selected in this study because it is appropriate for XXB, where lateral variations in velocity and temperature are insignificant (Yang et al, 2010).…”

Effects of May through July 2015 storm events on suspended sediment loads, sediment trapping efficiency, and storage capacity of John Redmond Reservoir, east-central Kansas

“…The relation between reservoir releases, water residence time, and sediment trapping efficiency may be used to manage reservoir sedimentation. Lee and Foster (2012) estimated that trapping efficiency of the reservoir could be decreased approximately 3 percent per year (equating to 56 acre-feet of storage) from current rates by altering outlet management practices specifically to reduce residence times within the reservoir.…”