Occasionally over the life of the pool water will have to be drained. Whether for the winter or repairs, all that water has to go somewhere. However, the chemicals used to support clean water are damaging to the local wildlife. You can take a few measures to prevent damage to the environment and the yard the pool occupies.
Balance the water to a neutral pH before draining, which should not be a problem as a normal pH balance in a pool stays pretty neutral. Highly acidic water could destroy the grass, plants, flowers and trees in your yard. If the water runs off into a neighbor's yard, it could also damage their landscaping.
Chlorine is particularly toxic to local wildlife and aquatic life when high levels, such as that in pool water, drains into the environment. To protect wildlife, do not add any chemicals to the pool 3 to 10 days before draining to remove all of the chlorine present. Before draining, test the water for chlorine, and only drain if the level is zero or extremely close to it. Even if you do not intend for the water to enter the storm drains, most likely at least some of it will.
The flat, level ground that was so essential when installing your pool can be your downfall when draining it. Depending on the capacity of your pool and the saturation level of the ground, your yard likely can't absorb all the water at once. To keep your yard from flooding, insert a hose attached to the spigot and turn on the water for a minute or two. Turn off the water, and remove the hose from the spigot, which will create a siphon and will drain the pool slowly. Move the hose around to different parts of the yard to prevent flooding. Stagnant water can begin breeding mosquitoes in 48 to 72 hours. If draining into your yard is your only option, drain the pool slowly over a period of a week to a week and a half to ensure that the water can be absorbed fully.
The storm drains in most towns and cities are for diverting rainwater from streets and yards. Not only are these drains not meant to handle large loads of water all at once, but they could also cause flooding and damage further down the drain line. They are not meant for draining of chlorinated water as the drains lead directly to local bodies of water. In many states, draining any pool or spa into a drainage ditch or storm drain is illegal. However, there are, in some cities, sanitary sewer systems that lead to the water treatment plant. Call your local water utility or environmental service to find out if your town has one of these systems and the best way to drain your pool.