Effects of stream channelization on the distribution of nutrients and metals

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THE EFFECTS OF STREAM CHANNELIZATION ON THE DISTRIBUTION OF NUTRIENTS AND METALS

by

C h a r l e s W. O'Rear, Jr. Department of Biology E a s t C a r o l i n a U n i v e r s i t y G r e e n v i l l e , North C a r o l i n a 27834

The work upon which t h e p u b l i c a t i o n i s based was s u p p o r t e d i n p a r t by f u n d s p r o v i d e d by t h e O f f i c e of Water Research and Technology, Department of t h e I n t e r i o r , t h r o u g h the Water Resources Research I n s t i t u t e of The U n i v e r s i t y of North C a r o l i n a as a u t h o r i z e d under t h e Water Resources R e s e a r c h Act of 1964, a s amended.

P r o j e c t No. ; A-080-NC

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TABLE OF CONTENTS

Page ACKNOWLEGDENTS

. . .

iii

. . .

ABSTRACT

.

LIST OF FIGURES

. . .

vii

. . .

LISTOFTABLES viii

. . .

CONCLUSIONS

AND

RECOMMENDATIONS

. . .

INTRODUCTION

METHODS . . . a .

. . .

Studyareas

. . .

Discharge measurements

. . .

Water sample analysis

. . .

Metalanalysis

. . .

Sediment analysis

RESULTS

AND

DISCUSSION. e e e

.

. . .

Discharge

. . .

Temperature

. . .

Dissolved oxygen

. . .

Conductivity

. . .

pH

. . .

Nutrients-Nitrogen

Nutrients-Phosphorus . . . a s . . . . .

. . .

Nutrients-Chicod Creek

. . .

Dissolved Metals

Metals-Sediment . . . m e . . . e

Metals-Insects and benthic organisms

. . . .

Aquatic Plants.Nitrogen. Phosphorus. and Metals

.

. . .

Meta1,pFis.h

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ACKNOWLEDGEMENTS

The f a c u l t y of t h e Biology Department have c o n t r i b u t e d t o t h i s p r o j e c t by t h e i r s u g g e s t i o n s , c r i t i c i s m , r e v i e w , and t h e i r a b i l i t y t o l i s t e n . With- o u t t h e i r s u p p o r t t h e accomplishment of t h i s s t u d y would n o t have been

p o s s i b l e .

The g r a d u a t e s t u d e n t s a s s o c i a t e d w i t h t h i s s t u d y ; J a y Chapin, Ed Grune, D a r r e l l Vodopich, and Dan Kornegay, were r e s p o n s i b l e f o r most of t h e f i e l d work and t h e i r a t t e n t i o n t o d e t a i l and d e d i c a t i o n was o u t s t a n d i n g .

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ABSTRACT

The p r o j e c t was d e s i g n e d t o d e t e r m i n e t h e d i s t r i b u t i o n p a t t e r n s of

n u t r i e n t s and m e t a l s i n c h a n n e l i z e d and u n c h a n n e l i z e d s t r e a m segments and t o d e t e r m i n e i f m o d i f i c a t i o n s o c c u r i n t h e d i s t r i b u t i o n of n u t r i e n t s . A d j a c e n t segments of S w i f t Creek, P i t t County, North C a r o l i n a were u s e d a s t h e s i t e s . An upstream segment c h a n n e l i z e d i n 1937 was used a s a r e p r e s e n t a t i v e n a t u r a l s t r e a m w h i l e a segment a p p r o x i m a t e l y one k i l o m e t e r downstream, c h a n n e l i z e d i n 1965, was u s e d a s a r e p r e s e n t a t i v e c h a n n e l i z e d s t r e a m . Sampling was performed from September, 1973, t h r o u g h November, 1974.

Flows i n t h e s t r e a m segment show a t y p i c a l p a t t e r n f o r e a s t e r n North C a r o l i n a w i t h h i g h f l o w p e r i o d s from J a n u a r y through A p r i l and August t h r o u g h September. The h i g h e s t f l o w s r e c o r d e d were d u r i n g A p r i l , 1974. Low f l o w p e r i o d s o c c u r r e d d u r i n g May t h r o u g h J u l y and October t h r o u g h December. The l o w e s t f l o w s were r e c o r d e d d u r i n g November, 1973. The median f l o w observed d u r i n g t h e s t u d y p e r i o d was 0.65 c u b i c m e t e r s p e r second (CMS), w i t h 75% of t h e f l o w s observed l e s s t h a n 4.0 CMS.

Water t e m p e r a t u r e s i n t h e n a t u r a l segment t e n d e d t o b e lower t h a n i n t h e c h a n n e l i z e d segment due t o a g r e a t e r canopy c o v e r i n t h e n a t u r a l segment. Average t e m p e r a t u r e s d u r i n g b o t h t h e w i n t e r and summer h i g h f l o w p e r i o d s , 12OC and 23°C r e s p e c t i v e l y , s t a y e d t o g e t h e r r a t h e r c o n s i s t a n t l y e x c e p t f o r a l a r g e d i u r n a l v a r i a t i o n d u r i n g t h e summer p e r i o d . During t h e low flow p e r i o d s o f e a r l y summer and l a t e f a l l a v e r a g e d i f f e r e n c e s i n t h e n a t u r a l and c h a n n e l i z e d segment exceeded 1.5OC and i n some i n d i v i d u a l measurements t h e d i f f e r e n c e s exceeded 4OC.

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Most of the nitrogen and phosphorus moved through both stream segments during the high flow periods. The highest concentrations were observed during the low flow period of October through December. Ammonia-N accounted for most of the increased nitrogen concentrations while particulate phosphorus accounted for the rise in total phosphorus. Nutrient concentrations in Chicod Creek were lower than the unchannelized segment of Swift Creek. Modification of the nutrient distribution patterns could not be directly

determined from the measured nutrient concentrations and flows. Other observations, such as longer times of travel in the unchannelized segment and the large amount of plant biomass produced in the channelized segment, still support the contention that nutrient modification could take place in natural segments and has in the channelized segment by conversion to plant biomass.

I

feel that it would be better to compare ratios of the nutrient fractions from similar watersheds so that longer stream segments could be used.

Dissolved metal concentrations between the two segments showed no significant differences. The highest c o n c e n t r a t i o n s o c c u r r e d d u r i n g the

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LIST OF FIGURES

Page Fig

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Fig

.

Fig

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Fig

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Fig

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Fig

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Fig

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Fig

.

Fig

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Fig

.

Fig

.

Fig. Fig

.

Fig

.

. . .

Location map of study areas

Seasonal stream flow pattern-Swift Creek

.

Seasonal water temperature pattern-Swift Creek Seasonal dissolved oxygen pattern-Swift Creek

.

Diurnal percent saturation pattern. June-

. . .

Swift Creek

Diurnal percent saturation pattern. October-

. . .

Swift Creek

Seasonal conductivity pattern-Swift Creek

. .

. . .

Seasonal pH pattern-Swift Creek

. . . .

Seasonal pattern. NH3-N-Swift Creek

Seasonal pattern. N02-N-Swift Creek

. . . .

Seasonal pattern. N03-N-Swift Creek

. . .

Seasonal pattern. TON-Swift Creek

. . .

Seasonal pattern. DIP-Swift Creek

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LIST OF TABLES

Page T a b l e 1. Land u s a g e p a t t e r n s i n Chicod Creek and S w i f t Creek

Watersheds.

. . .

.

. . .

5

T a b l e 2 . Y e a r l y summary of d i s c h a r g e measurements i n S w i f t

Creek.

. .

.

. .

.

. .

.

8

Table 3. S e a s o n a l summary o f d i s c h a r g e i n S w i f t Creek and

Chicod Creek.

. . . .

.

,

.

. . . .

.

10

Table

4.

Times of t r a v e l .

. .

.

. . . .

.

. .

.

. . .

11

T a b l e 5. S e a s o n a l summary of w a t e r t e m p e r a t u r e - S w i f t Creek

.

. . .

1 2 T a b l e 6. S e a s o n a l summary of d i s s o l v e d oxygen-Swift Creek.

. .

.

1 3 T a b l e 7. D i u r n a l oxygen-temperature measurements.

. .

.

. .

.

17 T a b l e 8. S e a s o n a l summary of c o n d u c t i v i t y - S w i f t Creek

.

. .

. . .

1 9 T a b l e 9. R e l a t i o n s h i p of d i s c h a r g e and c o n d u c t i v i t y -

S w i f t C r e e k .

.

. . .

.

. .

.

1 9

Table 10. S e a s o n a l summary of pH-Swift Creek.

. . . . .

. .

.

2 1

T a b l e 11. D i u r n a l pH changes, June-October-Swift Creek.

. .

.

. .

21 T a b l e 1 2 , S e a s o n a l summary of n i t r o g e n , u n c h a n n e l i z e d a r e a -

. .

,

. .

.

,

. . .

,

. . .

23

T a b l e 13. S e a s o n a l summary of n i t r o g e n , c h a n n e l i z e d a r e a -

. .

*

. .

. . .

. .

.

2 3

T a b l e 14. S e a s o n a l r e l a t i o n s h i p of f l o w t o n i t r o g e n d i s t r i b u t i o n -

.

. .

.

,

. . .

.

*

.

. .

* 26

T a b l e 15. R e l a t i o n s h i p of f l o w t o n i t r o g e n d i s t r i b u t i o n -

. . .

. .

. . .

. . . .

. .

2 6 T a b l e 16. S e a s o n a l summary of phosphorus-Swift Creek

. . . .

.

2 9 Table 17. R e l a t i o n s h i p of f l o w t o phosphorus d i s t r i b u t i o n -

.

. .

.

,

.

. .

.

2 9

Table 18. Summary of f i e l d o b s e r v a t i o n s - C h i c o d Creek

. .

.

32 T a b l e 19. Summary of n i t r o g e n and phosphorus l e v e l s -

Chicod Creek, June-August, 1974.

.

. .

.

. . .

32

T a b l e 20. S e a s o n a l summary o f d i s s o l v e d m e t a l s , c h a n n e l i z e d

a r e a - S w i f t Creek.

.

. . . .

. .

. . .

35

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Page Table 21. Seasonal summary of dissolved metals, unchannelized

area-Swift Creek,

. . . .

.

. .

.

. . . .

35

Table 2 2 . Cumulative metal content in ppm of sediments in channel-

ized and unchannelized stream segments

. . . .

.

3

7

Table

23.

Percentage ratios of exchangeable and extractable

metals to total metals.

. .

.

. .

.

. .

.

37

Table 2 4 . Description of sediments-Swift Creek.

.

. .

.

3 8

Table 2 5 . Percentage by weight of sediments below 4 phi

and percent weight loss on combustion.

.

. . . .

.

..

3 9

Table 2 6 . Metal Content of insects and benthic organisms.

. . .

..

41 Table 2 7 . Concentration ratios of benthic orgnaisms.

. .

.

42

Table 2 8 . Concentrations of nitrogen, phosphorus, and metals

found in rooted plants,

. . . .

. . .

43

Table 2 9 . Metal Content of fish found in channelized and

unchannelized segments-Swift Creek.

.

,

. . .

4 5

Table 3 0 , Metal content of fish found in unchannelized

segment only.

.

. .

. . . .

.

,

. . . . . . .

4 6

Table 31. Comparison of some of Odum's ecosystem attributes

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CONCLUSIONS

AND

RECOMMENDATIONS

Conclusions

1. During the period; September, 1973-December, 1974; high flows occurred during the months of January-April, August, and September while low flows occurred during the remaining months. The median observed flow was 0.65 CMS. During low flow periods, the flow characteristics of the channelized and unchannelized area differ; the channelized area having higher velocities and shallower depths.

2 . The lack of canopy and shallow water depths in the channelized area caused a significant rise in the water temperature.

3 .

A

greater water velocity and the large amount of plants and algae

in the channelized segment caused significantly more dissolved oxygen in this area. Diurnal saturation values in the channelized segment varied as much as

90%.

4.

The short segments used with a lack of precision in flow and chemical measurements prevented the determination of within-segment changes in nutrient or metal distributions.

5. No significant differences were found between the channelized and unchannelized segments in nitrogen or phosphorus levels. Seasonal differences noted are the result of runoff and dilution during high flow periods.

6.

Nutrient levels in Chicod Creek are significantly lower than those in Swift Creek due to the presence of waste treatment facilities in the Swift Creek watershed.

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During low f l o w p e r i o d s , m e t a l s v s . f l o w a r e n e g a t i v e l y c o r r e l a t e d and d u r i n g h i g h f l o w p e r i o d s t h e r e i s a p o s i t i v e c o r r e l a t i o n . The p r e s e n c e of a r e d u c i n g environment d u r i n g t h e l o w e s t f l o w s would f r e e m e t a l s t o t h e w a t e r column t h e n a s f l o w s i n c r e a s e t h e r e d u c i n g environment would be l o s t . A t h i g h e r f l o w s d i s s o l v e d m e t a l s would come i n t o t h e s t r e a m w i t h s u r f a c e r u n o f f .

8. The u n c h a n n e l i z e d s t r e a m segment t e n d s t o have g r e a t e r c o n c e n t r a t i o n s of s e d i m e n t r y m e t a l s , e x c e p t f o r g r e a t e r amounts o f z i n c . The

s o u r c e of t h e l a r g e r c o n c e n t r a t i o n of z i n c i n t h e c h a n n e l i z e d segment p r o b a b l y r e s u l t s from t h e e f f u l e n t o f an a d j a c e n t p i g farm. The h i g h e r p e r c e n t a g e of o r g a n i c m a t e r i a l i n t h e sediment o f t h e u n c h a n n e l i z e d a r e a p r o b a b l y a c c o u n t s f o r t h e h i g h e r c o n c e n t r a t i o n of t h e o t h e r m e t a l s .

9. Rooted a q u a t i c p l a n t s i n t h e c h a n n e l i z e d segment s e r v e a s a concen- t r a t i o n mechanism f o r n u t r i e n t s and m e t a l s d u r i n g t h e summer low f l o w p e r i o d c o n s e q u e n t l y t h e normal p a t t e r n of n u t r i e n t and m e t a l movement downstream i s a l t e r e d .

10. No d i f f e r e n c e s i n m e t a l c o n c e n t r a t i o n s f o r two s p e c i e s o f f i s h w i t h d i f f e r e n t f e e d i n g h a b i t s i n t h e two s t r e a m segments were found. D i f f e r e n c e s were found between largemouth b a s s and s u c k e r s i n t h e u n c h a n n e l i z e d segment f o r c o n c e n t r a t i o n s o f i r o n , z i n c and c o p p e r . 11. No q u a n t i t a t i v e judgement can be made from t h i s s t u d y on t h e d i r e c t

e f f e c t o f c h a n n e l i z a t i o n on n u t r i e n t and m e t a l d i s t r i b u t i o n , b u t q u a l i t a t i v e e v i d e n c e i s p r e s e n t e d t h a t shows c h a n n e l i z a t i o n can a l t e r t h e s e a s o n a l p a t t e r n o f n u t r i e n t and m e t a l movemnet t o r e c e i v i n g w a t e r s .

Recommendations I

1. A move d e f i n a t i v e s t u d y be made on t h e d i r e c t comparisons of p a r t -

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2 . M o d i f i c a t i o n s be made i n t h e d e s i g n of c h a n n e l s s o t h a t canopy i s

p r o v i d e d t o p r e v e n t t h e b u i l d u p of p l a n t m a t e r i a l d u r i n g low f l o w p e r i o d s .

3 . M o d i f i c a t i o n s b e made i n t h e d e s i g n of channels s o t h a t a g r e a t e r

d e p t h of w a t e r w i t h s l o w e r t r a v e l t i m e s can be m a i n t a i n e d d u r i n g low f l o w p e r i o d s . These m o d i f i c a t i o n s would have t o i n c l u d e p r o v i s i o n s f o r m a i n t a i n i n g canopy c o v e r t o p r e v e n t a q u a t i c p l a n t b u i l d u p d u r i n g t h e spring-summer p e r i o d t h u s p r o v i d i n g a more n a t u r a l ecosystem.

x i i

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-INTRODUCTION

The t r a n s p o r t o f m a t e r i a l s by North C a r o l i n a C o a s t a l P l a i n s s t r e a m s from t h e t e r r e s t r i a l p o r t i o n s o f t h e i r w a t e r s h e d s i s a n i m p o r t a n t l i n k i n u n d e r s t a n d i n g t h e c a u s e s and e f f e c t s of e u t r o p h i c a t i o n i n E a s t e r n North C a r o l i n a e s t u a r i e s . These s t r e a m s , i n t h e i r o r i g i n a l s t a t e , c o u l d be c o n s i d e r e d components o f mature ecosystems w i t h a low o u t p u t of n i t r i e n t s and m i n e r a l s b e c a u s e of i n t e r n a l c y c l i n g . Man's i n f l u e n c e on t h e s e e c o s y s - tems h a s c o n s i s t e d of p o i n t d i s c h a r g e s of d o m e s t i c and i n d u s t r i a l w a s t e s , p o i n t d i s c h a r g e s of w a s t e s from l i v e s t o c k and p o u l t r y o p e r a t i o n s , and t h e non-point, d i f f u s e d i s c h a r g e s r e s u l t i n g from a g r i c u l t u r a l o p e r a t i o n s and u r b a n i z a t i o n . A s l o n g a s t h e s t r e a m s y s t e m i s p a r t of a mature ecosystem and i t s a b i l i t y t o a s s i m i l a t e m a t e r i a l i s n o t exceeded, i t s n u t r i e n t and m i n e r a l o u t p u t s h o u l d remain low. An a d d i t i o n a l s t r e s s h a s been p l a c e d on many o f t h e s e s t r e a m s i n t h e l a s t twenty y e a r s , c h a n n e l i z a t i o n .

A l t e r a t i o n of t h e s e s t r e a m s by c h a n n e l i z a t i o n t h e o r e t i c a l l y s h i f t s t h e s e s t r e a m s from a m a t u r e system t o e a r l i e r s t a g e s where n u t r i e n t and m i n e r a l o u t p u t i s h i g h w i t h t h e a s s o c i a t e d open c y c l e s f o r m i n e r a l s and n u t r i e n t s .

There i s an o b v i o u s d i f f e r e n c e i n t h e p h y s i c a l c h a r a c t e r of c h a n n e l i z e d and u n c h a n n e l i z e d s t r e a m s . The u n c h a n n e l i z e d s t r e a m i s g e n e r a l l y a s e r i e s of p o o l s and s h a l l o w a r e a s i n t e r r u p t e d by d e b r i s w i t h a h i g h p e r c e n t a g e of

canopy c o v e r . The t i m e o f t r a v e l f o r a w a t e r mass i s g e n e r a l l y s l o w w i t h low v e l o c i t i e s . The c h a n n e l i z e d s t r e a m u s u a l l y h a s a u n i f o r m bed w i t h p o o l s becomming a p p a r e n t o n l y a t v e r y low f l o w s . The c h a n n e l becomes t h e f l o o d p l a i n d u r i n g low flows. There i s v e r y l i t t l e canopy s i n c e c l e a r i n g t h e s i d e s o f v e g e t a t i o n i s t h e common p r a c t i c e , t h i s a l l o w s t h e b u i l d up o f v e g e t a t i o n i n t h e s t r e a m bed.

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can provide environments for the mineralization of organic material and for changes in the distribution of nutrients. Since the possibility exists for the differential modification of water quality by channelized and unchannelized streams, this study was initiated to determine if these modifications could be documented in adjacent channelized and unchannelized stream segments. The specific objectives were:

1. To evaluate and compare modifications of dissolved nitrate and dissolved phosphate levels in natural stream segments and in channelized stream segments.

2 . To evaluate and compare modifications in dissolved essential micronutrient elements (iron, zinc, copper) and dissolved toxic elements (zinc, copper, lead) in

the two stream segments.

3. To compare distribution patterns of the metals in fish, bottom fauna, rooted aquatic plants, and sediments in the two stream segments.

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MATERIAL

AND

METHODS

S t u d y A r e a s

The s t u d y a r e a s a r e l o c a t e d i n P i t t County, N o r t h C a r o l i n a . The

u n c h a n n e l i z e d and c h a n n e l i z e d s t r e a m s e g m e n t s a r e on S w i f t C r e e k , s o u t h e a s t of Ayden, N . C. ( F i g u r e 1 ) . The c h a n n e l i z e d s t r e a m segment i s l o c a t e d up- s t r e a m from County Road # I 7 5 3 (Area A). The u n c h a n n e l i z e d s t r e a m segment i s l o c a t e d a p p r o x i m a t e l y 1 . 2 k i l o m e t e r s ( 0 . 7 5 m i l e ) u p s t r e a m from County Road ill753 (Area B ) . Each segment was a p p r o x i m a t e l y 460 m e t e r s (1500 f e e t ) l o n g . N e i t h e r o f t h e s t r e a m s e g m e n t s had plowed c r o p l a n d a d j a c e n t t o t h e s t r e a m .

The u n c h a n n e l i z e d s t r e a m segment was c l e a r e d and d i t c h e d d u r i n g t h e l a t e 1 9 3 0 ' s . No s t r e a m improvement work h a s o c c u r r e d i n t h e main c h a n n e l s i n c e t h a t t i m e a c c o r d i n g t o d r a i n a g e d i s t r i c t r e c o r d s a n d t h e l o c a l S o i l C o n s e r v a t i o n S e r v i c e O f f i c e . T h i s a p p e a r s t o b e a t y p i c a l s t r e a m improvem,ent h i s t o r y o f many streams i n E a s t e r n N o r t h C a r o l i n a . The b a n k s of t h i s s t r e a m segment a r e r e l a t i v e l y s t a b l e a n d s t r a i g h t s i d e d w i t h a few a r e a s showing e r o s i o n . The stream b e d , e x c e p t i n low e n e r g y e n v i r o n m e n t s a r o u n d d e b r i s and i n p o o l s a s w e l l as t h e l o w e r two t h i r d s of t h e bank i s a g r a y s i l t y c l a y . The d e p t h o f t h e c h a n n e l f r o m t h e s u r r o u n d i n g f o r e s t f l o o r was a p p r o x i m a t e l y

4 m e t e r s . The o l d s p o i l b a n k s w e r e d i s c e r n a b l e t h r o u g h most o f t h e a r e a and had b e e n b r e a c h e d by h i g h f l o w s i n s e v e r a l p l a c e s . I n s e v e r a l l o c a t i o n s t h e s p o i l b a n k s a c t a s a dam, h o l d i n g s u r f a c e water and f l o o d w a t e r i n t h e swamp a l l o w i n g i t t o r e t u r n t o t h e s t r e a m a t a s l o w r a t e . The canopy c o v e r o f t h i s s t r e a m segment was e s t i m a t e d t o b e 75 t o 8 5 p e r c e n t .

(18)

Fig. 1. Location map of study areas

Upper right 1, 2, & 3 Chicod Creek study area

Lower center

A

channelized study area

(19)

construction was completed. The stream bed of the channelized segment varied from 15 to 20 meters wide. During low flow conditions the stream meandered through the bed. Approximately 50 percent of the stream bed was covered with rooted vegetation during low flow periods. Trees on the southwest bank provided afternoon shade of the channelized segment but there was no overhead canopy. Erosion had exposed the gray clay in several areas along the banks of the channelized area but not in the stream bed.

The Chicod Creek segment used for cmmparision is located south of

Grimesland, Pitt Co.,

N.

C. Sampling locations where bridges at the crossing of County Roads /I1565 (1 on Fig. l), ill777 (2 on Fig. l), ill760 (3 on Fig. 1).

A

comparison of land-usage patterns in the two watersheds is shown in Table 1. There were no discernable instances of recent ditching in the area of sampling, but in several cases plowed farmlandcamewithin 20 meters of the stream

channel. There was a well-defined channel with a silty bottom composed primarily of fine sand and organic material. Canopy cover was estimated to be 60% to 70%.

Table 1

Land Usage Patterns in Chicod Creek and Swift Creek Watersheds* Swift Creek Chicod Creek Total acreage _{51,640 (25,5976 hectares)} _{35,100 (17,364 hectares)}

Cropland-percent _46.3

_44.4

Pasture-percent

1.4

1.0

Woodland-percent _43.5 _44.3

Miscellaneous-percent 10.3 _8.8

(20)

Discharge Measurements

Stream discharge was measured by the use of standard techniques with a current meter. A rating curve was established at the downstream end of both the channelized and unchannelized stream segments. A minimum of ten discharge measurements at each point was used to establish the rating curves. The rating curves were used primarily for establishing flows above 1 (one) cubic meter/ second (cms). Most low flow measurements were made with the current meter. Visual time of travel measurements were made during low flow over the entire length of each stream segment.

Water Sample Analysis

Field measurements of dissolved ozygen, pH, and conductivity were made using standard instruments: YSI Model 51A for dissolved oxygen, YSI Model

33

Conductivity Meter, and Fisher pH meter, Model 150. The above measurements were made at each water sample collection site.

Water samples for laboratory analysis were collected in plastic bottles and stored on ice. Upon return to the laboratory, samples for dissolved fractions were filtered using Gelman type E glass filters or Metricel type GA filters. All samples were refrigerated at 4OC. until analyzed, which was usually less than

24

hours. If samples were kept longer before analysis, they were frozen.

Total organic nitrogen was determined by Kjeldal digestion and measure- ment of the resulting ammonia-N with an ammonia probe. Ammonia-N in the

water was also measured with the probe. Nitrite-N and nitrate-N were measured by the diazotation and brucine methods respectively (EPA, 1971). Total

(21)

Metal A n a l y s i s

A l l r a e t a l s were measured by t h e u s e of atomic a b s o r p t i o n s p e c t r o p h o t o m e t r y . Water samples used f o r d i s s o l v e d m e t a l a n a l y s i s were a c i d i f i e d w i t h 1 m l 0 . 1 N HN03 p e r 100 m l sample and r e f r i g e r a t e d u n t i l a n a l y z e d . Organisms, b o t h p l a n t and a n i m a l , were wet d i g e s t e d w i t h a n i t r i c - p e r c h l o r i c a c i d m i x t u r e and t h e n a n a l y z e d f o r m e t a l s .

Sediment A n a l y s i s

(22)

RESULTS & DISCUSSION

Discharge

The summary of discharge data for the study areas in Swift Creek is shown in Table 2. Discharge measurements were taken in Swift Creek from September, 1973, through November, 1974. Chicod Creek was sampled from June, 1974, through August, 1974. The U. S.

G.

S. estimated 7 day110 year low flow for the Swift Creek Study area is 0.001-0.0014 CMS (0.04-0.05 CFS). No 7 day110 year low flow estimate was available for Chicod Creek.

The seasonal pattern of streamflow for the Swift Creek Study area is shown in Figure 2 and Table

3.

The pattern shown appears to be typical of streamflows in this area when compared to the U. S. G. S. gaging stations on Creeping Swamp, unchannelized, a tributary of Swift Creek, and 19.6 Km (12.2 mi) downstream from the study area.

Table 2

Yearly Summary of Discharge Measurements in Swift Creek Units are Cubic Meters Per Second (CMS)

Swift Creek

Mean

7 Median Range

-

N

(23)

Fig. 2. Seasonal stream flow pattern-Swift Creek channelized area

.

unchannelized area

(24)

There a r e two t r i b u t a r i e s e n t e r i n g S w i f t Creek between t h e c h a n n e l i z e d and u n c h a n n e l i z e d stream segments, one i s a n a t u r a l t r i b u t a r y and t h e o t h e r i s t h e e f f l u e n t from a waste t r e a t m e n t lagoon f o r a hog farming o p e r a t i o n . The n a t u r a l t r i b u t a r y showed a c o n s i s t a n t p a t t e r n of d i s c h a r g e l i k e t h a t of t h e u n c h a n n e l i z e d s t r e a m segment. The e f f l u e n t from t h e p i g o p e r a t i o n c o u l d n o t be measured a d e q u a t e l y b u t was e s t i m a t e d by measuring t h e l e n g t h of t i m e i t t o o k t o f i l l a one l i t e r sample b o t t l e , u s i n g t h i s method t h e d i s c h a r g e

?.

was n e v e r g r e a t e r t h a n 0 . 1 l i t e r p e r second.

S e a s o n a l Summary of D i s c h a r g e i n S w i f t Creek and Chicod Creek U n i t s a r e i n CMS

S w i f t Creek

Channelized

P e r i o d Me an Median Range N

Jan-Apr 9.4 6.7 0.8

-

1 8 . 8 14

May-July 0.6 0.3 0.2

-

1.6 25

Aug-Sep t 4.5 2.7 0.6

-

7.9 16

Oc t-Dec 0.9 0.6 0 . 1

-

2.2 1 8

Unchannelized Jan-Apr 8.2 6 . 5 0.8

-

1 8 . 8 1 2

May-July 0.4 0.2 0 . 1

-

1.0 1 4

Aug-Sep t 3.6 2.1 0.5

-

5 . 1 7

Oct-Dec 0.5 0.4 0.1

-

1.54 1 4

Chicod Creek

June-Aug

(25)

This effect was apparent during the high flow periods of August and September.

Chapin (1975), in a tributary of Swift Creek, Creeping Swamp, found that

macro benthic biomass in the unchannelized swamp increased during high flows

while the same biomass measurements in the channelized segment decreased dur-

ing high flows. High dominance and low diversity indices characterized the

channelized stream while the reverse was characteristic of the unchannelized

stream. Chapin attributed these characteristics of the benthic invertebrate

population to the relative instability of the channelized stream substrate

during high flow periods.

There appeared to be no distinct differences in the flow pattern of

Swift and Chicod Creeks. The major difference noted in the three areas was

the water velocity as measured by times of travel (Table

4).

All measurements

for Swift Creek were made the same day usually within

s

six hour time period.

Time of travel measurements were made during June, July, and October.

Table

4 Times of

ravel-~eters/Minute

Discharge

Swift Creek

Unchannelized

Channelized

(26)

Temperature

The temperature of the water in Swift Creek was directly related to the

characteristics of channel and flow as well as the ambient air temperature.

Table 5 and Figure 3 shows the seasonal variation in temperature of the

channelized and unchannelized stream segments, Appendix Table 1 shows the

yearly summary.

During high flow periods, January-April and August-September, the

velocity of the flow and the associated turbulence maintained the two stream

segments at essentially the same temperature. Since the two stream segments

were so close together, four temperature measurements were made approximately

2 kilometers (2.5 miles) downstream during both high flow periods. During

the January-April high flow period the temperature was 1 to 1.5 degrees higher

then in the channelized segment. These measurements were made on sunny days,

therefore, the lack of canopy allowed additional warming by the sun. During

the August-September high flow period the temperature was 0.5 to 1 degree

higher downstream.

Table 5

Seasonal Summary of Water Temperaure-Swift Creek

Channelized

Unchannelized

Period

**%*s .E.**

Range

-

N

Z2s.E.

Range

-

N

Jan-Ap

r

12.5k1.2

6-19.5

16

12.021.1 5.5-18

16 May-July

22.8k0.5

18-29

34*

20.8k0.3

18 -22.5

2

0 Aug-Sep

t

22.7k0.2

21-24.5

20 22.8k0.4

21.5-25.5

9 Oc

t-Dec

18.6+1. 8

14-24

6*

15.8+1.4

10 -21

8

(27)

During the low flow periods there was a statistically significant rise

in the water temperature between the channelized and unchannelized stream

segments. This rise in temperature can be attributed to the lack of canopy

in the channelized stream segment and the shallow water depth. Daylight

measurements of temperature during June indicate a difference of 2.g°C

between the downstream stations of the unchannelized and the channelized

stream segments. Daylight measurements during October show a 1.4OC differ-

ence between the two stream segments.

The observed differences in temperature in the channelized segment do

not appear to exceed known limits for the organisms known to be present in

this stream system. The temperature variations do contribute to a general

pattern of instability

in

the channelized stream segment.

Dissolved Oxygen

Dissolved oxygen concentrations in the two stream segments is related to

flow and the characteristics of the stream channel. The yearly summary of

oxygen concentrations is found in Appendix Table 1. The seasonal pattern is

shown in Figure 4 and Table 6.

Seasonal Summary of Dissolved Oxygen-Swift Creek

Channelized

Unchannelized

Period

W5S.E.

Range

-

N

I+S.E.

Range

-

N

Jan-Ap

r

9.5C0.8

2.8-14.8

16

9.550.8 4.0-15

16 May-

July

9.7+0.5*

5.4-16.3

32 6.2t0.2

4.6- 8.2

18 Aug-Sept

6.4k0.1

5.3- 7.2

20 6.3k0.2

5.2- 7.2

9 Oct-Dec

9.9+1.2*

5.6-14.8

6 5.1k1.2

1.8-10.2

8

(28)

Jan MW A L ~ Oct

A P r July Sopt Doc

Fig.

3.

Seasonal water temperature pattern-Swift Creek

channelized area

.

- -

Fig.

4.

Seasonal dissolved oxygen pattern-Swift Creek

.

(29)

No s i g n i f i c a n t d i f f e r e n c e s were found i n oxygen c o n c e n t r a t i o n s between t h e c h a n n e l i z e d and u n c h a n n e l i z e d s t r e a m segments d u r i n g h i g h f l o w p e r i o d s

(Jan.-Apr. and Aug.-Sept.). The d i f f e r e n c e s n o t e d i n t h e d i s s o l v e d oxygen c o n c e n t r a t i o n between t h e w i n t e r and l a t e summer h i g h f l o w p e r i o d s was r e l a t e d t o t e m p e r a t u r e d i f f e r e n c e s , t h e r e were no s t a t i s t i c a l d i f f e r e n c e s i n t h e p e r c e n t s a t u r a t i o n v a l u e s f o r t h e two t i m e p e r i o d s .

During low f l o w p e r i o d s (May-July and 0ct.-Dec.), t h e r e was a s i g n i f i - c n a t d i f f e r e n c e i n t h e oxygen c o n c e n t r a t i o n i n t h e two s t r e a m segments. P e r c e n t s a t u r a t i o n i n t h e c h a n n e l i z e d s t r e a m approached 100% f o r most

o b s e r v a t i o n s , and s e v e r a l t i m e s exceeded 100%. I n t h e u n c h a n n e l i z e d segment t h e p e r c e n t s a t u r a t i o n was between 50 and 75. A l l of t h e oxygen determina- t i o n s d i s c u s s e d h e r e were made between 1 1 : O O AM and 3:00 PM.

D i u r n a l oxygen measurements were made d u r i n g J u n e and October. The r e s u l t s of t h e s e s t u d i e s i s shown i n Table

7

and F i g u r e s 5 and 6.

S e v e r a l oxygen measurements were made a t n i g h t d u r i n g h i g h f l o w p e r i o d s t o d e t e r m i n e i f changes due t o b i o l o g i c a l a c t i v i t y could be d e t e c t e d . No changes were d e t e c t e d t h a t c o u l d n o t be a t t r i b u t e d t o i n c r e a s e d s o l u b i l i t y due t o lower n i g h t t e m p e r a t u r e s .

(30)

10 12 1 4 16 18 2 0 2 2 ii 2 4 6 e 1 0 12 '4 t t m e o f day D S T

Fig. 5. Diurnal percent saturation pattern, June-Swift Creek

.

-

t l m e o f day D \ l

Fig. 6. Diurnal percent saturation pattern, October-Swift Creek

.

(31)

Table

7 Diurnal Oxygen-Temperature Measurements

Channelized

Unchannelized

Time

-

Temperature

O C

Dissolved

Temperature

Oxygen,mg/l

O

C

June 13-14, 1974

October 23-24, 1974

Dissolved

Oxygen,mg/l

The channelized stream bed during low flows provides an environment for

the establishment of rooted aquatic plants, diatoms, and algae that is not

present except in isolated areas of the natural segment. Swicegood and Kriz

(1973) reported that aquatic weeds were a major problem in other coastal

plains streams so the situation with regard to the establishment of plant

communities in the stream bed is not unique to Swift Creek but appears to be

typical of channelized coastal plains streams.

The character of the plant communities in the channelized stream bed

changes from the summer to late fall low flow periods. During the summer low

flow periods, thirty to forty percent of the stream bed is covered with

emergent and underwater beds of rooted aquatic plants, the rest of the stream

bed including damp sand, is covered by algal mats and brown material. The

brown material was examined microscopically several times from different

locations and was composed of diatoms. After the late summer high flow period,

(32)

t h e r o o t e d a q u a t i c p l a n t s were swept downstream o r were i n a decomposed s t a t e ; a l g a l mats and d i a t o m s were r e e s t a b l i s h e d by t h e end o f October.

The oxygen regime i n t h e c h a n n e l i z e d segment of S w i f t Creek d u r i n g t h e low f l o w p e r i o d s n e e d s t o be c o n s i d e r e d i n d e t e r m i n i n g w a t e r q u a l i t y c r i t e r i a f o r oxygen. During low f l o w p e r i o d s , t h e r e i s a l a r g e d i u r n a l f l u c t i o n i n t h e amount of oxygen a v a i l a b l e f o r a q u a t i c organisms, t h i s combined w i t h t h e h i g h t e m p e r a t u r e s a s s o c i a t e d w i t h t h e uncanopied c h a n n e l i z e d segment could r e s u l t i n s t r e s s c o n d i t i o n s t o organisms i n t h e e a r l y morning h o u r s . T h i s

\

s t u d y e x t e n d s H a l l ' s (1971) s i m i l a r comments on piedmont North C a r o l i n a s t r e a m s t o c o a s t a l p l a i n s s t r e a m s .

C o n d u c t i v i t y

The c o n d u c t i v i t y of w a t e r i s an i n d i c a t i o n of t h e amount o f i o n i z e d d i s s o l v e d m a t e r i a l . G e n e r a l l y , c o n d u c t i v i t y h a s a n i n v e r s e r e l a t i o n s h i p w i t h flow i n r e l a t i v e l y n o n - p o l l u t e d s t r e a m s (Hem, 1 9 7 1 ) .

The s e a s o n a l summaries f o r S w i f t Creek a r e shown i n T a b l e 8 and F i g u r e 7 .

Y e a r l y summaries a r e shown i n Appendix Table 1. C o o r e l a t i o n a n a l y s i s was used t o t e s t f o r r e l a t i o n s h i p s of c o n d u c t i v i t y and f l o w . Table

9

shows t h e r e l a t i o n - s h i p s t e s t e d and t h e r e s u l t s . The low c o r r e l a t i o n s o b t a i n e d r e f l e c t t h e g e n e r a l p a t t e r n mentioned e a r l i e r and show t h e wide v a r i a t i o n t h a t i s c h a r a c t e r i s t i c of s t r e a m s i n t h e c o a s t a l p l a i n (Sherwani, 1971).

(33)

Table 8

Seasonal Summary of Conductivity*-Swift Creek

Channelized

Unchannelized

Period

Z+S

.E.

Range

-

N

3S.E.

Range

-

N

Jan-Ap

r

May-

July

Aug-Sept

Oct-Dec

*Units are umhos

Table

9

Relationship of Discharge and Conductivity-Swift Creek

Relationships*

Channelized-flows by season

Unchannelized-flows by season

Channelized-all flows

Unchannelized-all flows

Channelized-flows<4.O crns

Unchannelized-flows<4.0 crns

Channelized-flows<O.65 crns

Unchannelized-flows<0.65

crns

All flows, channelized

&

unchannelized

All flows, channelized

&

unchannelized

Flows<4.0 cms-channelized

&

unchannelized

Flows<0.65 cms-channelized

&

unchannelized

Correlation

Significance

Coefficient

Level

NS

*Both raw flows and log (base 10) flows were tested. The correlations

obtained were from log-transformed flows.

The pH of a natural water system is generally controlled by chemical

equilibria associated with the material dissolved in it and in poorly buffered

systems or highly productive systems by photosynthesis. The pH and buffering

capacity of most coastal plains creeks is generally low due to the low quantity

(34)

Jan M ~ Y A!g _{O c t}I

AFr July Sept _D&

Fig. 8. Seasonal conductivity pattern-Swift Creek

.

-

Fig.

7.

Seasonal conductivity pattern-Swift Creek

.

(35)

of d i s s o l v e d m a t e r i a l s and t h e r e l a t i v e l y l a r g e amount of o r g a n i c m a t e r i a l a s s o c i a t e d w i t h t h e low-land a r e a s .

The pH observed d u r i n g t h e s t u d y p e r i o d on S w i f t Creek i s shown i n T a b l e 1 0 , Appendix T a b l e 1, and F i g u r e 8. D i u r n a l pH changes a s s o c i a t e d w i t h changes i n p h o t o s y n t h e s i s a r e shown i n T a b l e 11.

There a p p e a r s t o b e v e r y l i t t l e pH change i n b o t h t h e c h a n n e l i z e d and n a t u r a l segments. The d i f f e r e n c e s n o t e d c a n be d i r e c t l y r e l a t e d t o t h e g r e a t e r amount of p h o t o s y n t h e t i c a c t i v i t y i n t h e c h a n n e l i z e d segment. T h i s i s i l l u s t r a t e d by T a b l e 11 t h a t shows d i u r n a l pH measurements t a k e n a t t h e same t i m e t h e d i u r n a l oxygen measurements were taken.

P e r i o d Jan-Apr May- J u l y Aug-Sep t Oc t -Dec

Time

-

S e a s o n a l Summary o f pH-Swift Creek

Channelized Unchannelized

2 S . E . Range

N

ZtS.E. Range

-

N

Table 11

D i u r n a l pH Changes, June and October-Swift Creek

Channelized Unchannelized

June

(36)

N u t r i e n t s - N i t r o g e n

The n i t r o g e n c y c l e i n n a t u r a l w a t e r s i s a l m o s t always r e l a t e d t o t h e b i o c h e m i c a l a c t i v i t y of t h e organisms i n t h e a q u a t i c community ( B r e z o n i k ,

1973). I n c o a s t a l p l a i n s s t r e a m s of North C a r o l i n a , c u l t u r a l a d d i t i o n s of n i t r o g e n t o n a t u r a l w a t e r s u s u a l l y t a k e s p l a c e i n t h e form of p o i n t and non-point d i s c h a r g e s from w a s t e t r e a t m e n t f a c i l i t i e s and s p e c t i c t a n k s , run- o f f and d r a i n a g e from a g r i c u l t u r a l o p e r a t i o n s , and r u n o f f from u r b a n a r e a s

(Howells, 1974; WRRI, 1969). The S w i f t Creek s t u d y a r e a s have a l l of t h e s e s o u r c e s o f n i t r o g e n l o c a t e d i n t h e w a t e r s h e d .

The s e a s o n a l summary and v a r i a t i o n i n n i t r o g e n i s shown i n T a b l e s 1 2 , and 1 3 , and F i g u r e s 9, 1 0 , 11, and 12. The y e a r l y summary i s shown i n Appendix T a b l e 2. The f o l l o w i n g a b b r e v i a t i o n s w i l l be u s e d t o d e n o t e t h e s p e c i e s of n i t r o g e n measured and d i s c u s s e d :

S p e c i e s Ammonia

-

N N i t r i t e

-

N N i t r a t e

-

N P a r t i c u l a t e and

d i s s o l v e d o r g a n i c

-

N

A b b r e v i a t i o n

TON

C o r r e l a t i o n c o e f f i c i e n t s were used t o e s t a b l i s h t h e p a t t e r n s o f n i t r o g e n d i s t r i b u t i o n w i t h flows. The c o r r e l a t i o n c o e f f i c i e n t s a r e shown i n T a b l e s 1 4 , and 15. A t t e m p t s were made t o u s e mass b a l a n c e t e c h n i q u e s t o d e t e r m i n e upstream- downstream changes i n e a c h segment. Lack of p r e c i s i o n and a c c u r a c y i n b o t h

f l o w d e t e r m i n a t i o n s and chemical a n a l y s i s of t h e w a t e r p r e v e n t e d t h e u s e o f mass b a l a n c e t o d e t e c t w i t h i n s t r e a m segment changes i n n i t r o g e n d i s t r i b u t i o n .

No s i g n i f i c a n t d i f f e r e n c e s were found between t h e c h a n n e l i z e d and unchannel- i z e d s t r e a m segments on a y e a r l y o r a s e a s o n a l b a s i s . The g r e a t e s t v a r i a t i o n was found from s e a s o n t o s e a s o n i n b o t h segments. The o r i g i n a l j u s t i f i c a t i o n f o r d i v i d i n g t h e s e a s o n s was t h e d i s c h a r g e p a t t e r n ( s e e F i g . 2 ) , b u t t h e f l o w

(37)

Table 12

Seasonal Summary of Nitrogen, Unchannelized Area-Swift Creek

Period

Jan-Apr

May-

July

Aug-Sept

Oct-Dec

3S.E.

.19+.07

.

041. 02

1.44+ .23

Range

.01-. 65

.O

-.I5

.44-3.0

N

12

11

12 E2S.E.

.31+.

05 .

16+.

02 1.212 .18

Range

.01-. 82

.05-. 36

.01-1.93

N

14

14 ZtS

.E.

.05+.

01 .02+.

003 1.332 .05

Range

.02-. 1

.01- .03

1.19-1.5

N

7

7 Z2S.E.

1.89t.61

.

03+.

007 .95t .26

Range

.06-7.2

.005-. 064

.01-2.5

N

14

10

15 TON

-

.63+ .23

.o

-2.9

12 1.52+ .07

.11-1.0

14 .16+ ,09

.05- - 7

7 .53t .19

.03-2.0

14 All nitrogen measurements are in mg-nitrogen11

Table 13

Seasonal Summary

of

Nitrogen, Channelized Area-Swift Creek

Period

Jan-Apr

May-

July

Aug-Sept

Oct-Dec

't2S.E.

Range

N

E2S.E.

Range

N

E2S.E.

Range

N

B2S.E.

Range

N

All ni

en measuremen

~ t s

are in mg-nitrogen11

TON

-

.4

+

.15

0 -2.3

14

.76+ -15

.1 -3.6

25 .07? ,003

.05- .1

15 .69+ .22

.05-2.88

(38)

Fig. 10. Seasonal pattern, N02-N-Swift Creek channelized area

.

-

J an MW _{A 9} _Ost

A-F July Sept Doc

Fig. 9. Seasonal pattern, NH3-N-Swift Creek

.

(39)

Fig. 12. Seasonal pattern, TON-Swift Creek channelized area

.

-

I

Jan M"Y Aug. O c t.

A 6r J U ' ) 9 5 t D%C

Fig. 11. Seasonal pattern, N03-N-Swift Creek

.

(40)

Table 14

Seasonal Relationships of Flow to Nitrogen Distribution-Swift Creek*

Period NH3 -N N02-N N03-N

-

TON Jan-Ap

r

Channelized

-.

82

-.

6 4 N S

-.

54

Unchannelized

-.

71 -.61 NS NS May-July Channelized

-.

21

-.

86

N

S N S Unchannelized NS

-.

62 NS NS Aug-Sept Channelized NS NS NS NS Unchannelized NS NS -.78 NS Oct-Dec Channelized -.53 NS NS .78

Unchannelized

-.

60

N

S NS .63 *All correlation coefficients are significantly different from 0 at the

.05

level. All flows used were log-transformed.

Table 15

Relationship of Flow to Nitrogen Distribution-Swift Creek

Flow

-

A1 1

Less than 0.65 CMS

More than 0.65 CMS

Area

-

Channelized &

Unchanneli zed Channelized only Unchannelized only

Channelized &

Unchannelized Channelized only Unchannelized only

Channelized &

Unchannelized Channelized only Unchannelized only TON

-

-.37

-.

39

-.

42

-.

43 -.

39

NS

-.

37

-.

46

(41)

Ammonia-N a p p e a r e d t o f o l l o w t h e most c o n s i s t a n t r e l a t i o n s h i p w i t h f l o w (Table 1 5 ) on a y e a r l y b a s i s . S e a s o n a l r e l a t i o n s h i p s t o f l o w were l e s s

c o n s i s t a n t (Table

1 4 ) .

The d i f f e r e n c e between t h e c h a n n e l i z e d and u n c h a n n e l i z e d s t r e a m segments i n ammonia-N c o n c e n t r a t i o n d u r i n g t h e August-September h i g h d i s c h a r g e p e r i o d i s d i r e c t l y r e l a t e d t o e f f u l e n t from t h e p i g farming o p e r a t i o n . Three ammonia and d i s c h a r g e measurements were made of t h i s e f f u l e n t d u r i n g t h e August-September p e r i o d . Ammonia-N measurements a v e r a g e d 8.6 mg/l and d i s c h a r g e averaged 0.01 cms. D i f f e r e n c e s n o t e d i n t h e c o n c e n t r a t i o n of ammonia between t h e low f l o w p e r i o d of e a r l y summer and t h e low f l o w p e r i o d of l a t e f a l l i s p r o b a b l y r e l a t e d t o t h e amount of o r g a n i c m a t e r i a l a v a i l a b l e f o r decomposition. S i n c e most of t h e o r g a n i c m a t e r i a l i n t h e w a t e r s h e d was f l u s e d by w i n t e r and s p r i n g r a i n s . The h i g h ammonia c o n c e n t r a t i o n s d u r i n g l a t e f a l l c o u l d t h e n r e s u l t from t h e decomposition of o r g a n i c m a t e r i a l f l u s e d i n t o t h e s t r e a m by t h e l a t e summer r a i n s and l e a f f a l l d u r i n g t h i s p e r i o d .

N i t r i t e - N d i s t r i b u t i o n w i t h f l o w s on a y e a r l y b a s i s do n o t show a

c o n s i s t a n t p a t t e r n e x c e p t when f l o w s a r e h i g h e r t h a n 0,65 crns (median f l o w ) . On a s e a s o n a l b a s i s a c o n s i s t a n t p a t t e r n was shown o n l y d u r i n g t h e January- A p r i l h i g h f l o w p e r i o d and t h e May-July low flow p e r i o d w i t h c o n c e n t r a t i o n s n e g a t i v e l y c o r r e l a t e d w i t h f l o w s a s would be e x p e c t e d .

(42)

(Gambrel1 e t a l , 1 9 7 4 ) , s i n c e most of t h e f l o w s g r e a t e r t h a n 0.65 cms would o c c u r d u r i n g f e r t i l i z e r a p p l i c a t i o n s i n t h e s p r i n g and t h e plowing u n d e r of

c r o p r e s i d u e s d u r i n g t h e August-September h i g h f l o w p e r i o d s .

T o t a l o r g a n i c n i t r o g e n on a y e a r l y b a s i s f o l l o w s a r e l a t i v e l y c o n s i s t a n t p a t t e r n (Table 1 5 ) w i t h flow b u t does n o t on a s e a s o n a l b a s i s (Table 1 4 ) . The r e l a t i v e l y h i g h p o s i t i v e c o r r e l a t i o n s found d u r i n g t h e October-December were unexpected. T h i s r e l a t i o n s h i p of t o t a l o r g a n i c n i t r o g e n t o f l o w i s p r o b a b l y r e l a t e d t o l e a f f a l l d u r i n g t h i s time p e r i o d and t o a g r i c u l t u r a l p r a c t i c e s i n t h i s a r e a . D i s c u s s i o n s w i t h f a r m e r s i n t h e a r e a and P i t t County A g r i c u l t u r a l E x t e n s i o n p e r s o n n e l e s t a b l i s h e d t h a t c r o p r e s i d u e s a r e most common i n t h e f i e l d s d u r i n g September and October, t h i s a c t i v i t y coupled w i t h t h e thunder- s t o r m a c t i v i t y d u r i n g t h i s p e r i o d and t h e l e a f f a l l would p r o v i d e i n c r e a s i n g amounts o f p a r t i c u l a t e m a t e r i a l w i t h i n c r e a s i n g d i s c h a r g e .

Nutrients-Phosphorus

The c u l t u r a l s o u r c e s of phosphorus i n t h e S w i f t Creek w a t e r s h e d a r e t h e same a s t h o s e of n i t r o g e n . An a d d i t i o n a l s o u r c e of phosphorus i n t h e c a s e o f b o t h r e c e n t l y c h a n n e l i z e d and t h e o l d c h a n n e l i z e d streams i s t h e e x p o s u r e t o

l e a c h i n g of Yorktown Formation s h e l l beds. T h i s f o r m a t i o n forms t h e s t r e a m bed and i s exposed on t h e bank of t h e u n c h a n n e l i z e d ( c h a n n e l i z e d 1937) s t u d y a r e a . T h i s same f o r m a t i o n p r o b a b l y forms t h e impervious l a y e r u n d e r t h e s a n d s e d i m e n t and s p o i l banks o f t h e c h a n n e l i z e d s t u d y a r e a .

(43)

Table 16

Seasonal Sumnary of Phosphorus-Swift Creek

Period

Jan-Apr

Channelized

Unchannelized

D.I.P.

T.P.P.

D.I.P.

T.P.P.

.24+.06

,21+.03

.15+.

03 .24+.

03 Range

.003-.

8 ,01-. 38

.02-.

3 .12-.

41 N

12

14

10

12 May-July

Z+S

.E.

.43+.

04 .46+.

03 .41+.06

.46+

.04

Range

.13--99

.19-.68

$04-.

7 .22-.

68 N

25

14

14 Aug-Sep

t

3S.E.

.41k.

24 .19+.

01 1.11+. 91

.454.19

Range

.06-4.0

.08-. 26

,045-6.5

.

17k1.

58 N

16

1 5

7

7 Oct-Dec

jZ2S.E.

.92+.28

2.19t.7

.79+.31

1.85 .6

Range

.07-4.2

.16-8.6

.l-4.0

.1 -6.8

N

20

15

16 All phosphorus measurements are in mg phosphorus/l.

Table 17

Relationship of Flow to Phosphorus Distribution-Swift Creek

Seasonal

Period

Jan-Apr

DIP

TPP

May-July

DIP

TPP

Aug-Sept

DIP

TPP

Oct-Dec

DIP

TPP

Channelized

Unchannelized

NS*

NS

Flow

-

Channelized

Unchannelized

All flows

DIP

NS

N

S

TPP

Flows less

DIP

than 0.65 CMS

TPP

Flows greater

DIP

than 0.65 CMS

TPP

(44)

Fig. 14. Seasonal pattern, TPP-Swift Creek channelized area

.

- -

Fig. 13. seasonal pat tern, DIP-Swif t Creek

.

(45)

August-September h i g h f l o w p e r i o d i n t o t a l p a r t i c u l a t e phosphate. T h i s r e s u l t e d from two measurements made d u r i n g r i s i n g f l o w s r e s u l t i n g from thundershowers i n t h e upper r e a c h e s of t h e w a t e r s h e d and t h e phosphorus b e i n g d i l u t e d by low p h o s p h a t e w a t e r from a t r i b u t a r y b e f o r e r e a c h i n g t h e c h a n n e l i z e d segment. T h i s was a l s o r e s p o n s i b l e f o r t h e l a r g e d i f f e r e n c e i n t h e means of d i s s o l v e d i n o r g a n i c p h o s p h a t e i n t h e two s t r e a m segment,

The g r e a t e s t s e a s o n a l movement of b o t h d i s s o l v e d i n o r g a n i c and p a r t i c u l a t e p h o s p h a t e o c c u r s d u r i n g t h e J a n u a r y - A p r i l p e r i o d . S i g n i f i c a n t amounts would a l s o b e t r a n s p o r t e d d u r i n g t h e August-September h i g h f l o w p e r i o d . The August- September movement of phosphorus may be t h e most s i g n i f i c a n t i n terms of

e s t u a r y e u t r o p h i c a t i o n . Hobbie e t a 1 (1972) r e p o r t e d t h a t t o t a l phosphorus c o n c e n t r a t i o n s i n t h e Pamlico R i v e r show i n c r e a s e s d u r i n g t h e August-September p e r i o d . S i n c e phosphorus i n t h e Pamlico i s n o t l i m i t i n g t h i s s e a s o n a l change i n phosphorus i n p u t h a s l i t t l e i m p o r t a n c e i n t h i s p a r t i c u l a r system. I n o t h e r North C a r o l i n a e s t u a r i e s where phosphorus i s l i m i t i n g t h i s s e a s o n a l i n p u t of phosphorus c o u l d p r o v i d e t h e n e c e s s a r y n u t r i e n t s f o r n u i s a n c e a l g a e blooms.

C o r r e l a t i o n s w i t h flow on b o t h a s e a s o n a l and y e a r l y b a s i s were c o n s i s t a n t w i t h what was e x p e c t e d , n e g a t i v e c o r r e l a t i o n s w i t h flow. The e x c e p t i o n was a p o s i t i v e c o r r e l a t i o n o f t o t a l p a r t i c u l a t e phosphorus w i t h f l o w d u r i n g t h e J a n u a r y - A p r i l p e r i o d .

Nutrients-Chicod Creek

(46)

Table 18

Summary of Field Observations

Chicod Creek, Pitt CO., N. C.

June, 1974-August, 1974

Dissolved

Water

Oxygen

Temperature

pH

Conductivity

_-

Flow

jL7S.E.

5.7550.33

6.220.04 0.05 (median)

Range

1.0 -7.9

19-24

5.7-6.7

54-150

0.01-2.8

N

33

8

3

2

7

, 8

No significant correlation was found between conductivities and flow in

Chicod Creek. Several oxygen determinations were made during pre-dawn hours

to determine if photosynthesis was contributing to day-time oxygen levels. The

average difference for three pre-dawn and three early afternoon oxygen determi-

nations was 0.9 mg/l. This indicates the similarity of primary production in

the unchannelized Swift Creek area and Chicod Creek.

The summary of nitrogen and phosphorus determinations is shown in Table 19.

Total particulate phosphorus was the only significant nutrient correlation with

flow. This value was -.54. All of the nutrient concentrations in Chicod Creek

are significantly different at the .05 level from those in Swift Creek during

Table 19

Summary of Nitrogen and Phosphorus Levels-Chicod Creek,

June-August, 1974

NH3-N

N02-N

N03-N

-

TON

-

DIP

-

TPP

3S.E.

.17*. 07

.02

6+. 007

.36+.

07 .04+.008

.204 .04

.27k.05

Range

.01-

.9

-005-.

074 -06-.95

.014-.11

.014- .57

.09-.88

(47)

(48)

D i s s o l v e d M e t a l s

Heavy m e t a l s i n an ecosystem have two a s p e c t s o f b i o l o g i c a l i m p o r t a n c e , t h e y a r e e s s e n t i a l p a r t s of b i o c h e m i c a l p r o c e s s e s i n an organism and t h e y can b e t o x i c i n e x c e s s i v e amounts. I n some c a s e s f o r a p a r t i c u l a r m e t a l t h e r e i s o n l y a s m a l l d i f f e r e n c e s e p a r a t i n g t h e e s s e n t i a l r e q u i r e m e n t and a t o x i c amount. I r o n , z i n c , c o p p e r , and l e a d were chosen a s r e p r e s e n t a t i v e of heavy m e t a l s i n t h i s s t u d y b e c a u s e o f t h e e s s e n t i a l r e q u i r e m e n t s o f t h e f i r s t t h r e e and t h e d e c r e a s i n g amounts r e q u i r e d f o r t o x i c e f f e c t s .

The s e a s o n a l summaries of t h e i r c o n c e n t r a t i o n s i s found i n T a b l e s 2 0 , and 21. The y e a r l y summary i s found i n Appendix Table 3. There were no s i g n i f i c - a n t d i f f e r e n c e s found between t h e c h a n n e l i z e d a r e a and t h e u n c h a n n e l i z e d a r e a e i t h e r on a s e a s o n a l o r y e a r l y b a s i s . The o n l y s i g n i f i c a n t d i f f e r e n c e n o t e d between s e a s o n s i n e i t h e r segment was t h e low f l o w p e r i o d of October-December. None o f t h e l e v e l s o f c o n c e n t r a t i o n found i n S w i f t Creek a r e c o n s i d e r e d t o x i c .

C o r r e l a t i o n c o e f f i c i e n t s t o t e s t f o r t h e r e l a t i o n s h i p of f l o w t o t h e d i s s o l v e d m e t a l s on a s e a s o n a l b a s i s were d e t e r m i n e d f o r i r o n and z i n c o n l y . Copper and l e a d were n o t t e s t e d b e c a u s e o f t h e i r e x t r e m e low l e v e l s . The o n l y s i g n i f i c a n t c o r r e l a t i o n f o r i r o n v s . f l o w , -.68, was found d u r i n g t h e low f l o w p e r i o d of May-July. The c o r r e l a t i o n c o e f f i c i e n t f o r z i n c was n e g a t i v e , t h e c o r r e l a t i o n c o e f f i c i e n t f o r i r o n d u r i n g t h e October-December low f l o w p e r i o d was a l s o n e g a t i v e . Even though t h e s e c o r r e l a t i o n c o e f f i c i e n t s were n o t s t a t i s t i c a l l y s i g n i f i c a n t t h e r e a p p e a r s t o b e a n i n v e r s e r e l a t i o n s h i p o f t h e d i s s o l v e d m e t a l s t o f l o w d u r i n g low f l o w p e r i o d s . S i g n i f i c a n t c o r r e l a t i o n c o e f f i c i e n t s f o r z i n c v s . f l o w were found d u r i n g t h e h i g h f l o w p e r i o d s o f J a n u a r y - A p r i l and August-September

.

These were .74 f o r t h e J a n u a r y - A p r i l p e r i o d and .64 f o r t h e August-September p e r i o d . I r o n v s . f l o w c o r r e l a t i o n c o e f f i c i e n t s , even though n o t s i g n i f i c a n t , were a l s o p o s i t i v e . These c o r r e l a - t i o n c o e f f i c i e n t s i n d i c a t e t h a t d i f f e r e n t mechanisms could be c o n t r o l l i n g t h e