Water lillies in farm pond

Question
The farm pond is about 30 years old.  This is the first year that we have had any problem with water lillies or some sort of lily in the pond.
We have had less rainfall than normal here and the pond water level is lower than in previous years. My question is: What can I do to eradicate these lily plants in my pond.. They are entirely around the outer edge of the pond.
Thank you

Answer
Hi Patsy,
Thanx for your question.  Farm ponds are out of my expertise however, if you can tell me your county and state, I can provide you contact information for your local Extension service.  I have worked with mine as a volunteer before here in Kansas and the service is a wealth of information and assistance.  I hope this helps.
Tom