You might try to apply for the SALT program from the usda. If your watershed qualifies for erosion control or water quailty control for a qualified district they will design, build and possibly even pay you for a pond.Depending on how your watershed is ranked(if you qualify) determines how much they will help w/ construction costs.Anywhere from 50%-100% based on ranking.They built 7 ponds/lakes for my grandfather,paid 100% construction costs and gave him small yearly payments just to maintain them. All because he ranked high on erosion and water quailty issues.