The thin reservoir reached 20% heat depletion faster than the thick reservoir. For the thin reservoir, all approaches (analytical and numerical with and without conduction) predicted <10 years before 20% heat depletion, whereas all approaches predict >20 years before 20% depletion for the thicker, base-case reservoir. 6. Reservoir temperature is more sensitive to conduction from the surroundings in cases with low flow rates (see ) or a high ratio of surface area to volume (e.g., the thin reservoir in Sec. 3.4).