Review of Top Down Water Storage Mixing Systems

Project ID: 6415
Principal Investigator: Merlynn Bender
Research Topic: Water Quality
Funded Fiscal Years: 2016
Keywords: None

Research Question

Is top-down mixing system technology valid? What are the benefits to large water storage reservoir water quality
and clarity?
Water storage reservoirs are large, generally static bodies of water. This can cause an assortment of undesirable
water quality issues and lower water clarity, especially during the summer months. Concerns include oxygen
depletion, algal blooms, heavy metals accumulation and taste and odor. There have been recent advances in
technology to address these issues. The system pumps water vertically downwards through a floating draft tube
using a mechanical impeller to produce visual and physical benefits from circulation that destratifies the water
column during summer months. The research being proposed is a review of this technology to determine its
relevancy to Reclamation and its partners. This would also provide relevant information in support of identifying
potential operational/management solution alternatives to improve water clarity in the Colorado-Big Thompson
(C-BT) Project's Grand Lake, a natural lake, where there is currently a proposed State of Colorado numeric water
clarity standard scheduled to be implemented in 2017. Under existing Project authority, Reclamation is exploring
various methods to improve and sustain Grand Lake water clarity as it relates to C-BT Project operations. The
methods used in this study could be applied in other Reclamation regions as public awareness of water quality
and water clarity issues increases.
This proposed research is an RD Priority that was unable to be funded at the time due to the limited Priority
funding cap.

Need and Benefit

Reclamation has not taken a hard look at this technology and its effect on water quality, its potential benefits, and
its advantages and disadvantages for use in large water storage reservoirs. The effect on water clarity issues is
equally unstudied. The information produced from this research could generally assist in future decisions related
to water storage reservoir management for water quality and development of options to address the proposed
State water clarity standard for Grand Lake.

Contributing Partners

Contact the Principal Investigator for information about partners.

Research Products

Bureau of Reclamation Review

The following documents were reviewed by experts in fields relating to this project's study and findings. The results were determined to be achieved using valid means.

Review of Top Down Water Storage Mixing Systems (final, PDF, 632KB)
By Merlynn Bender
Publication completed on September 30, 2016

A review of top-down mixers are presented in this report. Top-down mixers can improve lake and reservoir water quality in many specific water storage systems. Top-down mixers move oxygenated water from surface layers to depths thereby increasing release dissolved oxygen (DO) concentrations. Selected applications are reviewed in this report along with a presentation of advantages and limitations of this technology.


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Last Updated: 4/4/17