Thanks for everyones' replies. Not sure it's possible to enlarge the pond appreciably. Most years it's not at full capacity now. We get a lot of wind evaporation on the plains of Kansas. My lowest water level is "dry" and KDWP recommends 15' to prevent winterkill in western KS. I'm not sure I can get them 15' deeper but I guess anything would help at this point.
Thanks again!