Fon Koemans studied law in Utrecht, and completed his military duties, after which he worked for ten years at ABN Bank. In 1981 he became a board member and in 1991 chairman of The Nederlandse Waterschapsbank N.V. (NWB or Dutch Bank for Water Boards).

Mr Fon Koemans is also a member of the Task Force on Financing Water for All. This Task Force was formed at the end of 2005 and provided a cross-sector perspective on Innovative Financing Mechanisms for Local Actions for the World Water Forum in Mexico.