Here are the layers that I have:

* State / Province polygon file (With Area Field)
* County / Ward polygon (with no area field), but all the polygons are within the state boundaries
* Water ways for the whole province / state. (includes rivers, lakes, creeks, brooks, etc) with no area fields

Here is what I want to do:

* Determine the gross land area of counties without the rivers and lakes.

Notes:

* The area doesn't have to be extremely precise (nearest 5 sq km is fine with me)
* Has to work on ArcMap