I am being palgued with gnats all over my garden. it is impossible to go out there to work. The walls and fence panels are covered and hovering in the air and on the plants. I live near a resevoir and they are usually in swarms there. There is also a works yard at the back of the house for the water company and they are drilling a bore hole. Could this be the problem and any ideas how i get rid of them or at least reduce the numbers.