With current water levels this season, there is no water under the Isthmus Bridge. A short portage is necessary to get into Kinnaird Lake from Jackson Lake, or vise versa. It may be easier to paddle down to Jackson South Campsite and portage across from there. 

Due to past years of  high water levels, the portion of trail is closed for the Isthmuth Bridge that goes over the confluence of Jackson Lake and Kinnaird Lake is impassable as it has been damaged and is not suitable trail to be used.