Water quality summary for the Snake River and alpine lakes in Grand Teton National Park and John D. Rockefeller, Jr. Memorial Parkway: Preliminary analysis of 2015 data (Revised - 2019)

Levandowski, Mary; Ray, Andrew; Mellander, Kathryn; Whaley, Chad

This report summarizes discharge and water quality monitoring data for the Snake River and water quality moni-toring data for representative alpine lakes in Grand Teton National Park and John D. Rockefeller, Jr. Memorial Parkway for calendar year 2015. Results presented include annual and long-term discharge summaries and an evaluation of chemical conditions relative to state and federal water quality standards. These results are consid-ered provisional, and therefore may be subject to change. River Discharge Hydrographs for the Snake River at Flagg Ranch, WY, and Moose, WY, exhibit a general pattern of high early summer flows and lower baseflows occurring in late summer and fall. During much of 2015, daily flows at the Flagg Ranch monitoring location were similar to and below the 25th percentile of daily flows at that site. Peak flows at Flagg Ranch were well below average flows from 1983–2014 and occurred 24 days earlier in the year than the long-term average. Peak flows at the Moose monitoring station were similar to the long-term average. Daily flows at Moose gage were similar to the 25th percentile of daily flows through annual peak flows and then fell below the 25th percentil of daily flows for the remainder of the year. Peak flows at the Moose station occurred five days earlier than the long-term average. During summer months, the unnatural hydrograph at Moose exhibited signs of flow regulation associated with the management of Jackson Lake. Water Quality Monitoring in the Snake River Water quality in the Snake River exhibited seasonal variability over the sampling period. Specifically, total iron peaked during high flows. At the Snake River Flagg Ranch site, total iron levels also increased measurably follow-ing late summer storm events. In contrast, chloride, sulfate, dissolved sodium, total magnesium, and total calcium levels were at their annual minimum during the period of snowmelt. Water Quality Monitoring of Alpine Lakes Water quality in three monitored lakes (Surprise, Amphitheater, and Delta lakes) varied by lake and sampling date. Amphitheater and Surprise lakes had total nitrogen and total phosphorus levels below the EPA reference conditions for the Middle Rockies Ecoregion. Delta Lake had the highest total nitrogen and total phosphorus levels and generally exceeded EPA reference condition criteria for these nutrients.

Water quality summary for the Snake River and alpine lakes in Grand Teton National Park and John D. Rockefeller, Jr. Memorial Parkway: Preliminary analysis of 2015 data (Revised - 2019)

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