Modification of Runoff from Upland Watersheds - the Influence of a Diverse Riparian Ecosystem

Rhode R i v e r s y s t e m have shown t h a t a d i v e r s e w e t l a n d ( M i l l Swamp) h a s a s i g n i f i c a n t i m p a c t on n u t r i e n t r u n o f f f r o m u p l a n d w a t e r s h e d s . I n t h i s p a p e r we p r e s e n t d a t a t o d e m o n s t r a t e how w a t e r q u a l i t y p a r a m e t e r s change as s u r f a c e and s u b s u r f a c e w a t e r moves t h r o u g h d i f f e r e n t h a b i t a t s w i t h i n Mi 11 Swamp. M i 1 1 Swamp c a n b e d i v i d e d i n t o t h r e e h a b i t a t s : (1) a f l o o d p l a i n f o r e s t t h a t has been h y d r o l o g i c a l l y m o d i f i e d and f l o o d s r e g u l a r l y , ( 2 ) a f l o o d p l a i n f o r e s t t h a t r a r e l y f l o o d s , and ( 3 ) a w e t l a n d t h a t i s p r i m a r i l y d o m i n a t e d b y h e r b a c e o u s v e g e t a t i o n . W h i l e t h e r e a r e s e a s o n a l changes i n a l l s u r f a c e w a t e r q u a l i t y p a r a m e t e r s , f e w changes o c c u r a s s u r f a c e w a t e r moves t h r o u g h t h e t w o f o r e s t e d h a b i t a t s . I n c o n t r a s t , a1 1 p a r a m e t e r s change t e m p o r a l l y and s p a t i a l l y a s s u r f a c e w a t e r moves i n t o and t h r o u g h t h e h e r b a c e o u s h a b i t a t . Ammonium a n d p h o s p h a t e conc e n t r a t i o n s d e c r e a s e d u r i n g s p r i n g and w i n t e r months and i n c r e a s e d u r i n g summer months . N u t r i e n t changes i n t h e h e r b a c e o u s h a h i t a t a r e e s p e c i a l l y p r o nounced d u r i n g summer months when p e r i o d s o f a n o x i a o c c u r i n t h e w a t e r co lumn. N i t r a t e n i t r i t e and pH a l s o d e c r e a s e a s s u r f a c e w a t e r moves t h r o u g h t h e h e r b a ceous h a b i t a t . T h e r e a r e a l s o changes i n n u t r i e n t c o n c e n t r a t i o n s i n subs u r f a c e w a t e r , e s p e c i a l l y n i t r a t e n i t r i t e and t o t a l K j e l d a h l n i t r o g e n , i n t h e f o r e s t e d a r e a t h a t r a r e l y f 1 oods . A f t e r t w o y e a r s o f d a t a c o l l e c t i o n , i t a p p e a r s t h a t s u r f a c e w a t e r c h e m i s t r y i s p r i m a r i l y c o n t r o l l e d b y changes t h a t o c c u r as w a t e r moves t h r o u g h t h e h e r b a c e o u s p o r t i o n o f Mi 11 Swamp. Changes i n g r o u n d w a t e r c h e m i s t r y a p p e a r t o b e a s s o c i a t e d w i t h f o r e s t e d a r e a s w h i c h a r e n o t r e g u l a r l y f l o o d e d w i t h s u r f a c e w a t e r and where t h e w a t e r t a b l e e l e v a t i o n f l u c t u a t e s w i d e l y d u r i n g t h e y e a r .