The pH results for May were consistent with our findings in April, with sites showing only small changes from last month’s results, if any.
The air and water temperatures for the Greenville sites in May increased once again, with the air temperature average increasing by 3.3 degrees from April’s average of only 16C to 19.3C this month. The air temperatures ranged from 17C at Falls Park to 21.5 at Cedar Falls Park. The water temperatures also increased significantly, with the average water temperature increasing by 2.9C. The range of water temperatures this month were between 18C at both Swamp Rabbit Café and Falls Park and 20C at Greenville Tech Brashier.
May’s dissolved oxygen (DO) results ranged from 7.2 mg/L to 7.9 mg/L. Overall, the average DO levels only dropped 0.6 mg/L, but this came as a large decrease at some sites like Mauldin Road and Swamp Rabbit Café, which dropped 0.9 and 0.8 mg/L from April’s results, respectively. The consistent decrease in DO levels is once again expected due to the inverse correlation between water temperature and DO. Warmer water has less capacity for dissolved oxygen. We expect the DO levels to continue to decrease with an eventual plateau as temperatures increase throughout the spring and summer.
The E. coli bacteria results were higher this month than they were in April, but were still below the state-defined “high threshold” of 349 cfu/100mL with the exception of Cedar Falls Park, which only slightly surpassed the threshold at 400 cfu/100mL. This increase in E. coli colony forming units can likely be attributed to the noted presence of woody and plastic debris along the trail and, even more importantly, new evidence of stream bank erosion that occurred after the last major storm event on April 28, 2023 where the river was 6 feet above normal stream height as measured at the nearby USGS stream gauge. We will monitor this site’s E. coli and turbidity readings closely in the coming months. All other sites’ E. coli levels ranged from 66 to 266.67 cfu/100mL.
FORR has begun sampling water transparency by using a transparency tube, which quantifies the clearness (or clarity) of water. Color, algae, and suspended sediments can alter this result. In the Reedy, transparency is most likely to be impacted by sediments in the water column due to high runoff rates and failing streambanks due to the urban nature of our watershed. This measure of transparency can be converted and utilized to approximate water turbidity, which is a measure of the cloudiness of water. Turbidity can impact photosynthesis and water temperature and can be indicative of too much unmanaged stormwater runoff in the watershed. This month’s turbidity results ranged from 5 NTU at Falls Park and Greenville Tech Brashier and 27 NTU at Cedar Falls Park. The high turbidity at Cedar Falls Park can be attributed to the previously mentioned erosion issues due to recent rains. This higher result brings our average turbidity result across all sites to 10.8, which we hope to see decrease during our next sampling event.
May’s results and the SC state standards are included for comparison below. All results were within SC state standards.