The waters of earthly rivers are not crystal clear. Many of them are muddy and contaminated with sewerage. This wonderful river is called the River of the Water of Life, because of its life giving properties.
Earthly streams have their source in some mountain spring, but the River of Life has its source in the throne of God (22:1). In the centre of the City, probably on its summit, will rest the Throne of God, from under the seat of which shall flow down the crystal stream that shall feed that wonderful River of Life.
In this immense city there will be a street lined with trees, as are also the banks of a wonderful river. These trees are not mere shade trees, but beautiful fruit trees, called the Tree of Life, that bear twelve kinds of fruit, a different kind each month. The fruit of these trees is for the overcomers (Gen.2:7), and the leaves of the trees are for the healing of the nations that shall occupy the New Earth.
It is not implied that there will be any sickness, but the leaves are to preserve health, as Adam would have been preserved in health to live for ever if he had been allowed to continue to eat of the Tree of Life in the Garden of Eden (Genesis 3:22-24).
This confirms that the population outside New Jerusalem will live in their natural bodies, like Adam, but recovered from the imperfections brought on by sin, having their vitality renewed by the leaves of the tree.
"Tree of Life" is probably the name of its kind and, as happens with fruit trees, it will produce seeds so it will multiply and there will be enough leaves for the use of all the population on earth.
The River and the Tree of Life
1 And he showed me a pure river of water of life, clear as crystal, proceeding from the throne of God and of the Lamb.
2 In the middle of its street, and on either side of the river, was the tree of life, which bore twelve fruits, each tree yielding its fruit every month. The leaves of the tree were for the healing of the nations.
3 And there shall be no more curse, but the throne of God and of the Lamb shall be in it, and His servants shall serve Him.
Rev 22:1-3 (NKJV)