Which are two common forms of water storage?

The correct answer highlights two common forms of water storage: ground water and elevated tanks. Groundwater, which is water stored underground in aquifers, is a crucial source of drinking and irrigation water. It serves as a natural reservoir that can be tapped through wells. Elevated tanks, also known as water towers, are structures designed to hold water at height, providing necessary pressure for distribution within a municipal water system. This combination supports both the natural storage of water underground and the need for pressurized storage above ground, ensuring an efficient supply chain for water delivery.

In contrast, reservoir storage tanks and ponds primarily focus on surface water storage, which is less applicable when discussing the combination of forms mentioned. Similarly, underground tanks and elevated towers, while relevant, do not fully convey the broader context of water sources like groundwater. Lastly, ground water and atmospheric storage together do not represent two distinct forms, as atmospheric storage is not a recognized method of holding water in the same way as the other answers.