Intrepid cows have been taking impromptu dips and soiling the Waikato River - with Hamilton's city council sitting on the fence to save $8500.

The council received three complaints in the past year about cows entering the east side of the river from the capped Horotiu landfill land it leases to a farmer.

City council property manager Nicolas Wells said that rather than spend $8500 on a fence along 852m of riverbank, the council decided to ask the farmer to better manage his stock.

But the farmer was unsuccessful and the council has now decided to fence the property.