Just a question of how much wind do you get at your site I am not knocking windmills but have several customers that have installed them and not one that has returned the investment to the customer.
If you are going to invest $2000.00 why not spend the additional cost of electric[ $40.00 per month] for a system that works 24/7. If electric is at your site you can deliver over a mile easily air to your pond. If a stream water powered pump or solar if depth is not greater than 12 foot.
Good luck


Scott Trava
Catskill Pond
http://catskillpond.com
scott@catskillpond.com
Returning Catskill Waters To A Simpler Time
EST. 1923