Lemon grass plants are a natural and beautiful alternative for keeping mosquitoes away.
If you have standing water you are going to have mosquitoes, unless you can treat the water with some form of mosquito dunk.
Sorry, guess I wasn't thinking about standing water...in that case there are pellets..I forget the name...that you can sprinkle into the water and surrounding banks to kill the pests without hurting anything else. Call your local water dept. or maybe even DNR and ask them what they recommend.