Fox Creek Park Ecolological Assessment - Water Quality
IV. Water Quality Assessment
All North Carolina streams are classified according to their water quality. Fox Creek currently does not have a stream quality classification assigned by NC Division of Water Resources (NCDWR). Classifications are applied to streams, rivers and lakes, which define the best uses to be protected within these waters (for example swimming, fishing, drinking water supply) and carry with them an associated set of water quality standards to protect those uses.
NUTRIENT AND WATER QUALITY PARAMETERS
Water samples were collected in May 2023 to document existing conditions of primary in-stream nutrient and water quality measurements. To establish trends, sampling would need to occur on a routine basis, however the following parameters and results provide a snapshot of stream water quality as of 2
A Nutrient and Water Quality Results
Sampled nutrient and water quality parameters are listed below with water sample data from five sample sites listed in Table 1 below. Sample Site #1 is along the wetland tributary at the footbridge stream crossing and Sites 2 & 3 are along the primary Fox Creek channel (Figure 3).
Parameter Descriptions + NC regulatory limits
*NH3-N = ammonia-nitrogen; standard to protect trout waters = 1.0mg/L in summer and 2.0mg/L in winter
*NO3-N = nitrate/nitrite-nitrogen; standard to protect aquatic ecosystems = 10mg/L
*PO4 = orthophosphate (biologically available P); recommended limit <0.15mg/L to prevent downstream eutrophication
*Turb = turbidity (clarity); limit 50 NTU for aquatic life and 10 NTU for trout waters
*TSS = total suspended solids; no standard
*Cond = conductivity; no standard - dissolved ions in water can be variable
*Alk = alkalinity; no standard - low is normal for WNC but higher values protect against pH changes
*pH: recommended limit 6.0-9.0[1]
Ammonia (NH3) 0.08-0.21mg/L. These measurements are normal, and close to the regional average for the Blue Ridge. NH3 is the principal form of toxic ammonia. NH3 is toxic to freshwater organisms at concentrations between 0.53 and 22.8 mg/L. Toxic NH3 is both pH and temperature dependent: toxicity increases as pH and temperature decrease. Plants are more NH3 tolerant than wildlife, and aquatic invertebrates have greater tolerance than fish. In toxic conditions, hatching and growth rates of fish may be affected as well as structural development such as flaws in gills, liver, and kidneys tissues.
Nitrites (NO2) and Nitrates (NO3) - Measure of the Nitrogen present as Nitrite and Nitrate. NO2 and NO3 are low in Fox Creek with the wetland tributary having the highest concentration (0.08 mg/L) – all below the NC threshold. Nitrite in elevated levels is toxic to aquatic organisms and usually indicatesindicate contamination from fertilizer run-off.
Bacteria convert Ammonia to Nitrite (NO2) and then Nitrite to Nitrate (NO3) as part of the natural nitrogen cycle. Nitrate becomes toxic to most aquatic life at extremely elevated levels (>10 mg/L – far higher levels than found in Fox Creek). NO3 is also a necessary nutrient for plant and algae growth, but high nitrate levels in water are an indicator of fertilizer run-off contamination from adjacent lands or from elevated levels of wastewater. They are almost always associated with algal blooms, excess plant growth and oxygen depletion (which kills aquatic life).
Orthophosphate (PO4) - the bioavailable form of phosphorus, used by plants and algae for growth - is well below recommended base levels of 0.15 mg/L (or 0.05 mg/L P only) which is good. The elevated level of 0.12 mg/L at Site 3, at the northwest stream boundary, is likely due to runoff from yards upstream.
Turbidity – Turbidity, a measure of water clarity, is measured in Nephelometric Turbidity Units (NTU’s). Low NTUs signify relatively clear water during or after rain events while higher numbers represent less water clarity and higher levels of suspended solids. NTU levels of ten or lower are characteristic of relatively clean, clear water with low sedimentation. Sites 1 and 3 exceeded the NC trout water standard (10 NTU) but again, not surprising given recent rainfall, however brook trout have long been extirpated from the Swannanoa River and Fox Creek. All sites harbored turbidity levels lower than the NC standard of 50 NTU- the minimum for other aquatic life. Site 1, below the wetland, featured the highest turbidity levels, which make sense given slow-moving water and eroding streambanks near the sample site.
Total suspended solids (TSS) – like turbidity but a slightly more accurate measurement, TSS measures the actual dry-weight of solids larger than 2 microns within a 1-liter sample rather than light penetration through water (turbidity). Thus, sites ranged from a low of 9.2 mg/L at site 2 to a high of 36.7 at Site 1 (wetland drainage) again, mirroring turbidity and reflecting the slow-moving status in this channel.
Conductivity, Alkalinity, and pH are easily within range for a natural, forested stream in Blue Ridge. Conductivity and alkalinity do not have NC standards but are typically low in western NC and vary widely with changing geography. Higher levels are not necessarily bad but can indicate human impacts, with Sites 2 and 3 being more elevated than Site 1.
Fecal Coliform – Fecal coliform is elevated (310-460 CFU/100 mL) - not very surprising given the rain in the preceding days. The NC regulatory limit is based on 5 consecutive samplings in 30 days, recreation should be avoided if 200 CFU/100 mL or "looks muddy." The bacteria is likely coming from pet waste on land, from leaking pipes (Grovemont is an old neighborhood) or could just have been stirred up from the bottom and pond-sediments during the rain. Acceptable levels of fecal coliform in a 30-day mean is 126 cfu/100mL) and a single-sample number below 235 cfu/100mL t 575 cfu/100mL.
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