Groundwater attenuation of summer stream temperatures favors deeper intrusion depths into Lake George, NY

Groundwater inputs to two major streams along the southern end of Lake George attenuate summer temperatures resulting in deeper lake intrusion depths relative to other major streams. Between late April and early October, East and West Brook baseflow water temperatures generally were cooler than other major streams by ∼4 °C in mid-summer. Historical data for West Brook confirmed that the trend occurred as far back as 1970. As a consequence of cooler spring and summer temperatures coupled with higher salinity, deeper lake intrusion from these streams was hypothesized based on density calculations. Warmer streams entered the lake as overflow through late spring while East and West Brook intruded into the lake at depth. Upon stratification, East and West Brook intrude at or below the metalimnion while other monitored streams generally intrude at or above the metalimnion; by mid-August/early September all streams intruded below the metalimnion. High-resolution profiler data identified the presence of underflow during a fall storm event in 2014. Deeper intrusion depths of East and West Brook would supply organics and oxygen to the Caldwell Sub-basin hypolimnion which can potentially have both negative and positive effects on hypolimnetic oxygen depletion.