11.0  Smith Creek

            Two estuarine sites on Smith Creek proper, SC-23 and SC-CH (Fig. 11.1) were sampled.  Dissolved oxygen concentrations were below 5.0 mg/L on five of 11 occasions at SC-23 and four of 11 occasions at SC-CH, which was worse than the previous year (Mallin et al. 2003).  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 three of 11 occasions at SC-CH and two of 11 occasions at SC-23, an increase over last year.  These two stations also maintained some of the higher suspended solids concentrations in the Wilmington watersheds system.

            Total nitrogen concentrations increased over last year (Table 11.1), but algal blooms exceeding the state standard were not found in 2002-2003, an improvement over the previous year (Mallin et al. 2003).  Fecal coliform bacteria concentrations were above 200 CFU/100 mL on five of 11 occasions at SC-23 and four of 11 occasions at SC-CH, which was worse than the previous year (Mallin et al. 2003).  The geometric mean fecal coliform concentration was above the human contact standard at SC-23, and both stations but well above the shellfishing standard (14 CFU/100 mL) in the estuarine portion of the creek (Table 11.1).  BOD5 was sampled on 11 occasions in 2002-2003 at SC-CH, with a mean value of 1.5 mg/L and a median value of 1.6 mg/L, a decrease over last year. 

Table 11.1.  Selected water quality parameters in Smith Creek watershed as mean
(standard deviation) / range. August 2002 - September 2003.
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Parameter                              SC-23                  SC-CH
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Salinity (ppt)                          1.3 (2.6)                2.9 (5.3)
                                                0.1-7.8                   0.1-15.7 

Dissolved oxygen (mg/L)      6.1 (2.4)                6.3 (2.5)
                                                 3.6-10.5                4.0-11.2 

Turbidity (NTU)                     18 (12)                    24 (13)
                                                9-43                        8-54 

TSS (mg/L)                            13.1 (7.1)              24.0 (17.2)             
                                                1.3-26.9                 1.5-49.1 

Nitrate (mg/L)                        0.124 (0.100)        0.159 (0.139)
                                                0.017-0.296          0.019-0.437

Ammonium (mg/L)                0.125 (0.113)         0.100 (0.076)
                                                0.010-0.440           0.040-0.300

Total nitrogen (mg/L)             1.236 (0.545)        1.343 (0.357)           
                                                 0.737-2.726           0.737-2.060

Phosphate (mg/L)                  0.078 (0.191)         0.053 (0.032)
                                                 0.006-0.651           0.012-0.121

Total phosphorus (mg/L)      0.207 (0.428)            0.091 (0.035)
                                                0.009-1.487              0.040-0.166

Mean N/P ratio                         31.0                        12.7
Median                                      23.6                         8.4                       

Chlor. a (mg/L)                       8.5 (8.4)                      6.5 (6.1)
                                                1.5-30.9                     1.0-19.1

Fecal col. /100 mL                   224                         144
(geomean / range)                62-1950                    33-1840

BOD5 (mg/L)                             NA                        1.5 (0.4)
                                                                                  1.0-2.0
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