Here are a few suggestions to help with geese taking over your lawn. Let us know if you have any others that have worked for you.
Geese eat grass! They like to walk up out of the water and feed in an open area where they can look out for predators. They like short tender grass. Does your lawn fit the bill? Try one or all of these tips.
Create a natural shoreline buffer area with perennial wildflowers and shrubs - Sweet gale and red osier dogwood like to grow right at the water's edge and geese can't get over it. Leave soft bulrush and sedges to grow along shore. They also can't see if predators are hiding behind them. Add more plants like native wildflowers and attract monarch butterflies and other wildlife while deterring the geese.
If you have grass along the shore allow it to grow long. Try growing fine fescue grass varieties as geese prefer to eat Kentucky bluegrass. Eco-lawn is one brand. Southview and Botanix sell fescue seeds in bulk too. A bonus is that fescue grass needs no fertilizer, doesn't need very much water and has deep roots.
Eagle kites can scare the geese. http://www.geesedamage.com/geesecontrol2.htm
Don't use corn gluten fertilizer as the geese love it!
Short fences can work along the shoreline. Fishing line strung across the shoreline works very well as the geese can not see it until they touch it and then back off. Just remember it's there!
Good luck!