This study analyzes water-stable isotope composition by analyzing the impact of forest thinning on lodgepole pine depth-to-water uptake and water-use strategies. Lodgepole pine's primary source is spring snowmelt and shifts to rely on deeper soil water to maintain water uptake. There was no effect of decreased stand density on depth-to-water uptake. It will become more critical that we know how much water forests are using and which strategies trees use to sustain their water supply.