Your water feature will be the most popular bird bath in your
neighborhood lol. I have a friend that installed a large water feature
in his yard but it has fish in it and the pumps and filters keep the
water clean and circulating. If I were you I'd buy some activated carbon
and put it where the water passes over and that should help keep the
water fresh for some time. Pet stores that sell fish have the activated
carbon.
I also use some activated carbon in my potting soil to keep the soil
fresh. Good luck on your oudoor water feature.