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Description: The extraction of felsic melts, from crystallizing crustal magma reservoirs, is essential for the chemical evolution of the crust and is a phenomenon preceding some of the largest eruptions on Earth. The physical properties of residual melt and magma and the time at which the conditions remain appropriate for melt extraction are the most important factors controlling the efficiency of melt extraction and the distribution of melt in magma reservoirs. We use rhyolite-MELTS simulations to evaluate the physical evolution of crystallizing granodioritic (or dacitic) hydrous magma (i.e. ≥1 wt.% H2O) at 200 MPa. These results allow us to estimate extraction velocities of residual melt and to identify the optimal conditions at which melt segregation occurs. We additionally estimate the time that magma reservoirs of different thicknesses spend within the window that is best suited for magma extraction. Hydrous magmas that attain water saturation after 40 wt.% crystallization (rheological locking point) are best suited for melt extraction. In fact, once water-saturation is achieved, the rate of release of latent heat of crystallization increases while the viscosity of the residual liquid and crystal-liquid density contrast remain favorable for melt segregation. We test our findings on the Takidani pluton (Japan) because it shows clear evidences of residual melt segregation from crystallizing magma, and was associated with caldera-forming eruptions. In agreement with geochemistry, the calculations show that most of the melt-rich body at the top of the pluton was formed once the pluton crystallized to 40-50 wt.% and water-saturation was achieved. Estimates of the duration of cooling in this system suggest that residual melt properties were appropriate to allow the formation of a single melt-rich lens at the top of the reservoir. Our results can be generalized to upper crustal magma reservoirs and suggest that sufficiently large upper crustal reservoirs containing granodioritic (i.e. dacitic) magma with more than 3 wt.% H2O can produce large melt-rich caps at the top of partially crystallized magma within relatively short timescales. In H2O-poorer magmas the time available for melt extraction is not sufficient for complete extraction of the residual melt, which, therefore, accumulates in isolated pockets. The tendency of water-poorer magmas to form melt-rich lenses within partially crystallized magma may decrease our capacity of detecting eruptible magma using geophysical methods in volcanic systems such as Yellowstone.