A lake side view of the reservoir.
The Reservoir of Eternity is said to represent the naturally recycling flow of water that travels throughout the village of Uzushiogakure and isle of Land of Whirlpools. Most notably once, funneled through the water systems of Uzushiogakure the water composed of the flowing streams seems to have been purified and gifted with regenerative and soothing properties. The water itself is as pure as can be, undergoing a series of natural and man-mad filtration making it a much useful resource for the island. At the very base of the village is where the known Reservoir exists, collecting all the water that travels from the peak of Uzushiogakure throughout its vast streams and canals. From then, the reservoir stretches out into the island as it spans throughout landmarks such as the Forest of Wonders and even has a stream that leads into the Cave of Echoes. Ultimately, the Reservoir of Eternity leads the water out into the Great Sea, where the highly advanced pump systems funnel the water back to the top of Uzushiogakure's Waterfall in order for the water to cycle continuously. This adds to the effect of the purified and health benefiting water given from the Reservoir.
The reservoir as it continues out through the island.
The reservoir seems to be home to many fish and marine creatures, depending on the size and depth of the area a person is in. Most notably where the Great Sea starts is where the most fish would be, especially up streams and near the Forest of Wonders is where the Grizzly Bears find most of their salmon catch. The Reservoir of Eternity provides much of the wildlife of Uzushiogakure and its island an added sense of longevity and serenity. The water compared to other samples from various parts of the Shinobi World seemed to differ greatly, having an added effect to it possibly from the abundance of flowing natural energy within the island. When applied to plants the water has served to double growth and fertility as opposed to normal water.
Various houses and structures seem to be built along the reservoir, spanning from the village itself. There also seems to be ferry rides that travel throughout the transportable regions of the reservoir, allowing villagers and travelers to travel across and venture some of the islands natural hot spots and scenic areas. The reservoir itself is maintained by the village of Uzushiogakure and preserved from being tainted or corrupted.
A stationary post building along the Reservoir.
With many scenic views and hot spots the Reservoir of Eternity is known as a sacred water source to the island and treated as such. It seems that the water plays a big role in sustaining most of the life to the island and its luscious greens. Away from the village the Reservoir seems like an actual reservoir as opposed to the various streams and canals that it is composed off throughout the village. Only once the water reaches the bottom of the village does its masses grow greatly as the streams connect with-one another to form the giant pool of water known as the Reservoir of Eternity as it flows throughout the island. It is known to be a serious violation of Uzushiogakure's law to litter and disrupt the natural flow of the lake, thus causing severe jail time or crucial punishment for such offense such as waterboarding; in order to enforce that the water is not be tampered with.