Blue Mountain Lake Watershed Monitoring Program: 2021 Report
Adirondack Watershed Institute
Brendan Wiltse, Elizabeth Yerger, Lija Treibergs, Joline Hall, Connor Vara, Corey Laxson, & Daniel Kelting
The Blue Mountain Lake watershed has been monitored by the Adirondack Watershed Institute in one form or another for the past 25 years. In 2015, the program was changed from one that performed nutrient analysis on specific segments of two tributaries (Museum and Potter Brooks); to one that takes a more comprehensive look at the five major streams flowing into the lake. The goal of this enhanced program is to gain a better understanding of nutrient loading to the lake and the impact of road deicers. To support the upgraded program, each stream was instrumented with stage recorders and in-stream conductivity meters. This report covers the past six years of monitoring.
Correlation between the stream height recorded by the Levelogger and discharge for the study streams was excellent, with coefficient of determination values (R2) ranging from 0.89 to 0.99. With these relationships we were able to successfully quantify the volume of water entering Blue Mountain Lake at 30 minute intervals from May 2015 through September 2021.
The stream water entering Blue Mountain Lake tended to be acidic in the early spring, and circumneutral the remainder of the field season. This is a common pattern in many Adirondack watersheds and is primarily related to acidic snow melt. The streams typically had moderate acid neutralizing ability.
The greatest export of phosphorus and nitrate came from Museum Brook. The elevated concentrations are almost certainly related to the permitted discharge from the Adirondack Museum. Overall, nutrient export to the lake is quite low from all of the tributaries (including Museum Brook) and is within the range of nutrient export observed for least impacted streams in the AWI database.
The eastern side of the Blue Mountain Lake watershed is significantly influenced by road salt. In general, export of sodium and chloride to the lake increases with road density in the sub watersheds.
Correlation between the in-stream conductivity measurements recorded by the Hobo conductivity meters and chloride concentration for the salt impacted watersheds was excellent, with coefficient of determination values (R2) ranging from 0.82 to 0.96. The successful development of the conductivity – chloride model allowed us to quantify salt export from the Blue Mountain Lake sub-watersheds at 30 minute intervals.
Beaver Brook and Minnow Brook West are the two sub-watersheds that have no salted roads, and thus serves as a good benchmark for the non-impacted condition. The median export coefficient of chloride from these watersheds ranged from 4 to 5 g/ha/day, which is similar to other non-impacted watersheds in the AWI database (2-10 g/ha/day; AWI unpublished data). Conversely, sub-watersheds of Blue Mountain Lake with salted roads experienced median chloride exports that were 25 to 100 times greater than the least-impacted condition.
We observed a clear signal that a significant proportion of the salt applied to roadways is migrating to the groundwater. The concentration of chloride increased substantially during the low flow period of summer and early autumn in all three of the salted watersheds. Because streams are supplied primarily by ground water during this time, increased concentration during base flow periods are indicative of groundwater contamination.
