Which modern use of grassland is the most beneficial for the protection of water resources in the Polish Carpathians is scarcely known; thus, the deep outflows from organically, extensively, semi-intensively and intensively used and unused grasslands between 2019 and 2022 were measured. The studies showed that use impacted the process of deep infiltration, but the differences were clearest between the areas where management was reduced to a minimum (lowest outflow) and the areas which were mown most often (highest outflow). No effect of fertilisation was detected. To intensify groundwater recharge, it is evidently necessary to mow vegetation twice or three times per season; more frequent mowing changed the characteristics of the vegetation in an undesirable way. The fallowing of grasslands proved to be a practice unfavourable to groundwater resources.