Modeling the water-quality effects to the Klamath River from drain recirculation Completed

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Overview

A recent report published by U.S. Geological Survey explores what could happen to nutrient loads in the Klamath River when water from the Klamath Straits Drain is diverted from the river into the Ady Canal. The results of this study could help resource managers decide how to best reduce nutrient loads. 

The first 20-miles of the Klamath River, called the Link-Keno reach, flows between the outlet of Upper Klamath Lake from the Link River Dam downstream to Keno Dam. The Klamath Straits Drain is a 10.1 mile long earthen channel that transfers water north and west into the Link-Keno reach of the Klamath River. The drain is necessary to empty water from within the Klamath Project and the Lower Klamath National Wildlife Refuge. 

Poor water quality is well-documented in the Link-Keno reach.  Water quality issues in the reach are due in part to nutrients, organic matter, and/or algae coming from Upper Klamath Lake, Klamath Straits Drain, and other tributaries. The Klamath Straits Drain inputs high nutrient loads into the river, especially in the spring.

The latest report, published August 25, looks at the feasibility of addressing high nutrient loads by recirculating Klamath Straits Drain water away from the river into the Ady Canal during certain times of the year.  

Under typical conditions the Ady Canal diverts water from the Klamath River, flowing southeast to supply irrigated crop land and the Lower Klamath National Wildlife Refuge.  Since Ady Canal diverts water from the Klamath River, recirculation replaces water taken from the river with water from the Klamath Straits Drain. This trade-off ensures total water volume in the Klamath River is unchanged.  

Evaluating different scenarios 

The researchers simulated three recirculation scenarios using water-quality computer models for the Klamath River’s Link-Keno reach and the Klamath Straits Drain. Scenario zero, or the base case, is configured with the actual environmental conditions that occur with no recirculation. Specific recirculation scenario results are then compared to the base case.  

Scenario one examined year-round recirculation of all available Klamath Straits Drain Water into the Ady Canal. Compared to the base case, year-round recirculation led to significant reductions in the annual average daily loads of nutrients released into the Klamath River from Klamath Straits Drain. These load reductions were observed consistently throughout the year for all constituents, and in many cases, the reductions were within the current water quality requirements, particularly for nitrogen and phosphorus loads after June. 

Scenario two also examined year-round recirculation. However, the Klamath Straits Drain flow into Ady Canal was limited by the planned pipe capacity on the F-FF pump plant at 120 cubic feet per second. Despite this limitation, compared to the base case, scenario two also resulted in significant reductions in the annual average daily loads of nitrogen and phosphorus. 

The third scenario examined limited seasonal recirculation May through September with flow limited to 120 cubic feet per second. Compared to the other scenarios this approach resulted in the lowest reductions in nutrient loads. However, scenario three balances the need to avoid recirculation into Ady Canal in the spring due to salinity concerns, while still allowing the Klamath Straits Drain to meet or exceed its water quality requirements in the summer. 

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Model Limitations 

As with any modeling project there are limitations to consider. This study provides insights solely into the effects of recirculation on water quality (nutrients, 5-day biochemical oxygen demand) in the Klamath River and Klamath Straits Drain and doesn’t include other changes in water management.   

This work does not account for potential restoration or water-quality improvement projects in the Klamath Project beyond the indicated recirculation scenarios or areas. Additionally, this work does not assess results of situations where recirculation may be combined with other remediation actions. The updated model represents a new tool that can be used to better evaluate the degree to which other-water quality improvements and recirculation might interact under different future scenarios with a goal toward improving water quality in the Klamath River. 

Water-quality modeling in the Link-Keno reach extends back at least 25 years. The USGS, Bureau of Reclamation, and Watercourse Engineering collaborate to conduct field and experimental work that inform new models. This study builds upon those efforts to help resource managers balance complex water needs in the Klamath River Basin.