Hydrologic and Nutrient Balances for the Upper Klamath Lake Basin in Water Years 1992-2010

Jul 26, 2012

Prepared for Klamath Tribes Natural Resources Department by Aquatic Ecosystem Sciences LLC in association with W. Walker, Ph.D. and J. Walker, M.Eng., Environmental Engineers

Summary: This report describes the development of hydrologic and nutrient budgets for Upper Klamath Lake (OR) for a 19-year period (WY1992 - 2010). This analysis utilizes substantial hydrologic and water quality data collected by various agencies in the lake, lake outflow, major tributaries, sub-watersheds, and agricultural areas adjacent to the lake, portions of which were restored to wetlands over the WY 1998-2010 period. Relatively minor refinements to WY 1992- 1998 budgets are made to reflect adjustments to the historical hydrologic data, additional water quality data from pumped agricultural areas and restored wetlands, and an improved method for computing daily nutrient loads based upon daily flow and biweekly water quality measurements at the major monitoring sites. Time-series trend analyses were also performed for flow, nutrient load, and concentrations in each inflow and in the overall lake nutrient budget terms (total inflow, outflow, storage, retention) to determine whether changes occurred over the WY 1992-2010 time period in response to management efforts or other factors. Finally, an analysis was performed to differentiate between background and anthropogenic nutrient sources based upon spatial variations in unit area export and flow-weighted-mean concentration across watershed monitoring sites.

Citation: Walker, W.W., J. D. Walker, and J. Kann. 2012. Evaluation of Water and Nutrient Balances for the Upper Klamath Lake Basin in Water Years 1992-2010. Technical Report to the Klamath Tribes Natural Resources Department, Chiloquin, OR. July 2012. 50 pp +Appendices.