11.0  Smith Creek

              Two estuarine sites on Smith Creek proper, SC-23 and SC-CH (Fig. 11.1) are normally sampled; however, SC-23 was not sampled in 2004 due to construction activities.  Discussion of Smith Creek is thus limited to the SC-CH station on the bridge at Castle Hayne Rd.  Dissolved oxygen concentrations were below 5.0 mg/L on four occasions between May and September 2004.  Thus, low dissolved oxygen continued to be a water quality problem in Smith Creek (Appendix B).  The North Carolina turbidity standard for estuarine waters (25 NTU) was exceeded on two of seven occasions at SC-CH, similar to last year.  Suspended solids concentrations in Smith Creek were second only to Barnards Creek in the Wilmington watersheds system.

Nutrient concentrations remained similar to last year's levels (Table 11.1), and algal blooms exceeding the State standard were not found in 2004, similar to the previous year (Mallin et al. 2004).  Fecal coliform bacteria concentrations were above 200 CFU/100 mL on two of seven occasions at SC-CH, approximately the same as last year (Mallin et al. 2004) and all months tested well above the shellfishing standard (14 CFU/100 mL) in the estuarine portion of the creek (Table 11.1).  BOD5 was sampled on seven occasions in 2004 at SC-CH, with a mean value of 1.5 mg/L and a median value of 1.3 mg/L, a very slight decrease over last year. 

Table 11.1.  Selected water quality parameters in Smith Creek watershed as mean (standard deviation) / range. January - September 2004.
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Parameter                                                           SC-CH
                                                            Mean (SD)                 Range
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Salinity (ppt)                                      2.3 (3.6)                      0.0-15.7                                               

Dissolved oxygen (mg/L)                5.9 (2.9)                      3.1-11.4                                               

Turbidity (NTU)                                 19 (10)                        8-38                                               

TSS (mg/L)                                        20.1 (8.6)                   11.0-37.0                                               

Nitrate (mg/L)                                    0.117 (0.133)            0.040-0.380 

Ammonium (mg/L)                            0.096 (0.068)           0.040-0.240 

Total nitrogen (mg/L)                       1.443 (0.348)            1.070-2.010                                               

Orthophosphate (mg/L)                   0.025 (0.022)            0.005-0.060 

Total phosphorus (mg/L)                 0.101 (0.070)            0.070-0.150                                               

Mean N/P ratio                                  32.0
Median                                               31.0                       

Chlor. a (mg/L)                                   4.5 (4.1)                      0.7-9.0                                               

Fecal col. /100 mL                            104                              27-673
(geomean / range)               

BOD5 (mg/L)                                    1.5 (1.2)                      0.8-4.1

BOD20 (mg/L)                                   5.7 (3.4)                     1.8-12.9
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