The exact water quantity varies based on a few factors. Considering its pot size, a smaller pot may call for about a cup of water, while a larger pot could require a liter or more. Given the root depth of the 'arrowhead plant', which is generally shallow, providing a thorough watering until water runs out the drainage holes ensures adequate absorption. Over-time, as the plant grows, the water requirement may increase. It's important to evaluate water needs on a case-by-case basis considering the plant's size and growth rate.