The Obelisk of Water is located on the Water Obelisk Island off the shore of Catherby. It can be reached by climbing the ladder near the black dragons in Taverley dungeon. Players may only grapple from the island to Catherby, players cannot grapple from the shore to the island.
The obelisk is used to charge an unpowered orb into a water orb using the Charge Water Orb spell (with level 56 Magic, 3 cosmic runes and 30 water runes). A staff of water, or another staff that provides water runes, is recommended. A water orb is needed to craft a water battlestaff.
An effective route for charging multiple orbs is to bank in Catherby, grapple over White Wolf Mountain and head south to Taverley dungeon. Upon navigating the dungeon reaching the obelisk, the player can then charge, bank and repeat as required. This method requires a mithril grapple and any crossbow of mithril or higher quality, 39 Ranged, 36 Agility and 35 Strength. Level 70 or 80 Agility is very helpful for navigating Taverley dungeon more quickly.