What is the term for a tank that rests on the ground and has a height greater than its diameter?

The correct term for a tank that rests on the ground and has a height greater than its diameter is "Standpipe." Standpipes are vertical tanks that serve various purposes, including water storage and distribution in water systems. They are characterized by their tall, slender shape, which allows them to maintain pressure in the water distribution system as well as provide a volume of water for fire fighting and peak demand periods.

In contrast, a reservoir typically refers to a larger body of water, often created by damming rivers or other large-scale storage. A silo is usually associated with the storage of grain or feed and does not fit the context of water distribution. Meanwhile, a storage tank is a more general term that can refer to any container used for storing liquids but does not imply the specific proportions indicated in the question. Therefore, the distinctive characteristics of the standpipe make it the correct answer.