Water p o l l u t i o n assoc ia ted w i t h l a n d use a c t i v i t i e s (i.e., nonpo in t source p01 l u t i o n ) has r e c e i v e d p a r t i c u l a r l y d e t a i l e d s t u d y w i t h i n t h e Great Lakes Basin. Through a s e r i e s o f U.S.-Canadian i n v e s t i g a t i o n s c o o r d i n a t e d by t h e I n t e r n a t i o n a l J o i n t Commission's P o l l u t i o n f rom Land Use A c t i v i t i e s Reference Group (PLUARG), a comprehensive overv iew o f nonpo in t source p01 l u t i o n i n t h e Great Lakes was developed ( I n t e r n a t i o n a l J o i n t Commission, 1978, 1980, 1983). These s t u d i e s r e v e a l e d t h a t l a n d use a c t i v i t i e s adverse ly impact g r e a t lakes wate r q u a l i t y . A g r i c u l t u r a l l a n d use was s i n g l e d o u t as a ma jo r source o f sediments, n u t r i e n t s and p e s t i c i d e s impac t ing severa l reg ions , i n c l u d i n g Green Bay. Saginaw Bay and much o f t h e western and c e n t r a l bas ins o f Lake Er ie . These s t u d i e s i n d i c a t e d t h a t . a l though t h e l a n d area d r a i n i n g i n t o Lake E r i e occupies o n l y 11.5% o f t h e t o t a l l a n d area i n t h e Great Lakes Basin, Lake E r i e t r i b u t a r i e s c a r r i e d 58% o f t h e t o t a l t r i b u t a r y suspended s o l i d s l o a d e n t e r i n g t h e Great Lakes ( I n t e r n a t i o n a l J o i n t Commission. 1978). Maps o f u n i t area phosphorus y i e l d s f o r t h e Great Lakes i n d i c a t e d t h a t t h e l a r g e s t aggrega t ion o f l ands w i t h h i g h u n i t area phosphorus y i e l d s occur red i n t h e watersheds d r a i n i n g i n t o t h e western and c e n t r a l bas ins o f Lake Er ie . These h i g h sediment and phosphorus losses a r e assoc ia ted w i t h t h e i n t e n s i v e row c rop a g r i c u l t u r e which dominates l a n d use i n l a r g e p o r t i o n s o f t h e Lake E r i e Basin. Consequently, a g r i c u l t u r a l nonpo in t

p o l l u t i o n has been s t u d i e d most e x t e n s i v e l y i n t h e Lake E r i e Basin.