Water Quality Monitoring of Possum Creek and Noxontown Pond, Delaware. Final Project Report. Submitted to: GreenWatch Institute, Inc.

Transcription

1 Water Quality Monitoring of Possum Creek and Noxontown Pond, Delaware Final Project Report Submitted to: GreenWatch Institute, Inc. Submitted by: Kyle Castillo, College of Engineering and Ms. Maria Pautler and Ms. Jennifer Volk, College of Agriculture and Natural Resources University of Delaware Diana Burk and Peter McLean St. Andrew s School Middletown, Delaware December 22, 2015

2 Table of Contents Acknowledgements.. 3 Project Background and Objectives..4 Background...4 Objectives.. 6 Project Methodology...6 Project Results..8 Project Summary and Conclusions..14 References

3 Acknowledgements This report summarizes the findings of an undergraduate research project conducted by Kyle Castillo, College of Engineering, at the University of Delaware (UD), under the supervision of Maria Pautler and Jennifer Volk from UD s College of Agriculture and Natural Resources (CANR). Funding for this project was provided by the GreenWatch Institute, Inc., St. Andrew s School, and UD CANR. The authors greatly appreciate the advice and assistance provided by Diana Burk and Peter McLean at St. Andrew s School. Additionally we would like to thank Andrew Homsey at UD s Water Resources Agency for providing the maps and land use chart contained within this report. We also appreciate the analytical support provided by the UD Soil Testing Program, which conducted analyses of water samples collected from Possum Creek and Noxontown Pond during the fall of Any questions or requests for information related to this report should be submitted to Maria Pautler at mpautler@udel.edu. 3

4 Project Background and Objectives Background: We have received funding from the GreenWatch Institute, Inc. for the past four years, which has enabled us to improve our understanding of the water quality of Noxontown Pond (which flows into the Appoquinimink River) and to develop specific monitoring techniques to improve our understanding of the inflows of pollutants, such as nutrients, into the Pond. Our most recent efforts, as detailed in this report, are a complement to the report submitted to GreenWatch in May 2015, entitled Soil Health and Water Quality at St. Andrew s School, Delaware. The former report focused on monitoring stormflows into the pond during the 2015 winter months. This report focuses on similar stormflow monitoring during the 2015 fall months. Figure 1. Noxontown Pond and surrounding area. 4

5 Figure 2. Possum Creek Watershed and approximate locations of sampling sites. Sample sites Figure 3. Land use of the Possum Creek Watershed. Land Cover in Possum Creek Watershed 4% 7% 19% 70% Developed Agriculture Forest Wetlands 5

6 Objectives: To build on past water quality monitoring efforts in Noxontown Pond and recommendations that were developed for best management practices on surrounding agricultural lands, we have this year begun looking at how those practices may ultimately impact water quality through more focused monitoring efforts along a tributary draining to Noxontown Pond, namely Possum Creek, which ultimately drains into the Appoquinimink River. Task 1: Continued Water Quality Monitoring For the winter 2015 project work, it had been decided with the St. Andrew s School staff that we would target our storm monitoring along a transect of Possum Creek, a tributary to the Pond. There were three locations which were all accessible by foot during the winter months: both footbridges over the creek and the on Noxontown Pond itself. Our initial goal for this second round of project work was to use the monitoring protocol established for the winter months and continue sampling storm events from the three locations between April and October 2015 to additionally capture spring, summer, and fall storm events. Task 1: Continued Water Quality Monitoring Project Methodology Due to the unavailability of a UD undergraduate student intern during the entire seven-month period of April October 2015, an adjustment was made to the timeline to sample after storms during the fall months of September, October, November, and early December Due to the inaccessibility of the Upper Footbridge in September caused by dense plant growth and nesting bees, it was decided to sample halfway between the Upper Footbridge and Lower Footbridge to ensure the intern s safety. (A sample was not taken at the Upper Footbridge or the halfway point on 9/13/2015 at the intern s discretion as he awaited further instruction from the investigators.) The investigators focused on collecting one water sample from each location during all precipitation events from September through early December A total of five storms were sampled over this fall period - on average, one event every three weeks. Samples were collected on Sunday afternoons, which coincided with the undergraduate intern s availability around his class schedule. Storms that were sampled varied in size from three approximately one-inch rain events to an almost five-inch rain event on 10/4/2015. On each occasion, samples were collected from downstream to upstream. 6

7 Table 1. Storm sample collection dates and times at three locations along Possum Creek and Noxontown Pond during the fall of Date Halfway to Upper Footbridge Lower Footbridge Precipitation Amount (inches) 9/13/2015 not collected 4:00 PM 3:45 PM /4/2015 1:38 PM 1:20 PM 12:53 PM /1/2015 3:09 PM 2:55 PM 2:35 PM /15/2015 2:17 PM 2:00 PM 1:35 PM /6/2015 1:55 PM 1:43 PM 1:15 PM 1.06 In situ measurements of temperature, dissolved oxygen, and ph were made in the field during or immediately following each storm event. (Due to the inaccessibility of the lab at St. Andrew s by the intern on 12/6/2015, ph and dissolved oxygen measurements were not taken on that date.) In addition, a one-liter sample was collected at each of the three locations for laboratory analysis after three initial rinses with Creek/Pond water. From the Creek locations, care was taken to not disturb the bottom sediments as the Creek was always too shallow to fully submerge the bottle. From the Pond location, the sample was collected at approximately two feet (0.6 meter) below the water surface. To prevent biological growth during transport, the one-liter sample was kept on ice in a cooler and then stored in a refrigerator until laboratory measurements could be performed. Each sample was analyzed for dissolved ammonium nitrogen (ammonium-n) and nitrate nitrogen (nitrate-n), dissolved orthophosphate (ortho-p), total nitrogen (Total N), and total phosphorus (Total P) by the UD Soil Testing Program (UDSTP). Water samples analyzed by the UDSTP for dissolved ammonium-n, nitrate-n, and ortho-p were first filtered through 0.45-um filter paper and then analyzed colorimetrically. Total N and P were determined on unfiltered samples by persulfate digestion and colorimetry. Table 2. Water quality analyses conducted on samples collected from Possum Creek and the T- dock of Noxontown Pond during the fall of Parameters measured (units) Method Performed by In the field In the lab Temperature ( o C) Dissolved Oxygen (ppm=mg/l) ph Dissolved Ammonium-N (mg/l) Dissolved Nitrate-N (mg/l) Dissolved Orthophosphate (mg/l) Total Nitrogen (mg/l) Total Phosphorus (mg/l) Electric Probe (SAS) LaMotte Kit (SAS) Electric Probe (SAS) Colorimetric Colorimetric Colorimetric Digestion, Colorimetric Digestion, Colorimetric Castillo Castillo Castillo UDSTP UDSTP UDSTP UDSTP UDSTP 7

8 Task 1: Continued Water Quality Monitoring Project Results Visual Observations Prior project water quality assessments of Noxontown Pond have focused on summer months when the effects of eutrophication are most evident as algal blooms and murky conditions. Earlier this year, the project work focused on the winter months and investigated a tributary corridor draining to the Pond rather than just the Pond itself. This round, the work has focused on the same sampling areas during the fall months to gain more insight into seasonal variability. The investigators observed that the Pond continued to have murky water throughout the sampling period, while the water draining from Possum Creek was at times clearer but sediment-laden conditions were frequently observed. Potential contributions of field erosion and sediment transport from surrounding agricultural fields and riparian corridors were not assessed in this round of project work. Table 3. Visual observations of water color and condition during sampling of Possum Creek and Noxontown Pond in the fall of Date Halfway to Upper Lower Footbridge Footbridge 9/13/2015 This is an observation of the Upper Footbridge location: Brownish-green; Stream appears to be extremely shallow and littered with soil debris. Greenery and plant life have also considerably overgrown the entire site area, and ecosystems have sprouted up. (The intern decided that he could not safely sample here; no alternative sample was taken on this date.) Clear-brown; Water is clear and flowing regularly. Significantly colder than water at the T- dock. Greenish; Water appears green in color, with mossy residue floating around. Considerably warm and only slightly murky. 10/4/2015 Brownish-clear; New site is located between Upper Footbridge and Lower Footbridge. Upper Footbridge is still covered with greenery. New site appears much deeper in water level than Upper Footbridge or Lower Footbridge. Stream is polluted with fine organic matter. Crystal clear; Some organic matter floating instream. Water level appears to be much deeper than usual Murky-gray; A little warmer than usual. Some dusty debris and organic matter can be seen floating around the sampling area. 8

9 11/1/2015 Dark and murky; Water appears the same as at the Lower Footbridge. Stream is heavily polluted with leaves, sticks, and other fine organic matter. Again, silty-clay soils and fines seem to dominantly pollute the site 11/15/2015 Blackish-brown; Site appeared to be much more shallow than in previous sampling periods. Site is also heavily polluted with soils, sticks and other debris. Water was barely clear, even where shallow. 12/6/2015 Mostly clear; Warmest of the three sites. Midstream appears to be generally clear, with gravel visible through the water. Border-line of the stream appears polluted with leaves and dissolved fines. Water stream appears to be flowing at a fast rate. Dark and murky; Water is noticeably deeper than usual. Very dark, murky appearance. Heavily soiled with organic debris and fines. Stream also appeared to be flowing at a slower rate than observed in previous outings. Clear, but still slightly murky; Water was heavily polluted with organic sediment. Many fallen leaves litter all over the site. Greenish-clear; Water is heavily polluted with sediment from runoff. Water level appears to be deeper than usual. Stream is border-lined with leaves and other organic debris. Brown and murky; Water has debris and runoff material visibly present. Plenty of organic material present in water as well. Murky brown; Water appears fairly cleaner than previous sampling periods. Very small organic matter can still be seen floating around, although not very apparent. Murky-green; Visibility is nearly zero. Water appears to be generally clean, with little organic debris present. 9

10 Table 4. Images from the Possum Creek and Noxontown Pond sites during the fall of Date Halfway to Upper Lower Footbridge Footbridge 9/13/ /4/ /1/ /15/ /6/2015 Parameters Assessed and Comparison of Results to Water Quality Ecological Indicators and Drinking Water Standards Following the methods listed in Table 2, each sample was assessed for a number of constituents both in the field and through laboratory analyses. We were primarily interested in data related to nutrients (nitrogen and phosphorus) and dissolved oxygen, as these parameters have both human and ecological health implications. The USEPA has established a drinking water standard for nitrate-n of 10 mg/l. If concentrations exceed this value, caution should be taken consuming the water as negative health effects could occur in certain fractions of the population especially the young, old, and those with weakened immune systems. In addition, the Delaware Department of Natural Resources and Environmental Control has established concentration thresholds for freshwater streams to assess if a waterway is impaired by nutrients. The threshold value is 3.0 mg/l for Total N and mg/l for Total P. Additionally, there is a freshwater quality standard for dissolved oxygen of 5.5 mg/l daily average concentration where the instantaneous minimum shall not be less than 4.0 mg/l. Often, when nutrient concentrations exceed the threshold values, dissolved oxygen concentrations fall below their standards and characteristics of eutrophic conditions (algal blooms, fish kills, reduced biodiversity) are observed. 10

11 The following sections describe and graphically depict the monitoring data from storm samples collected from Possum Creek and Noxontown Pond during the fall of Temperature Throughout the course of the monitoring period, water temperatures decreased as the fall progressed. As seen with the Upper Footbridge site in the winter months, the halfway point between the Lower and Upper Footbridges stayed the warmest with respect to water temperature due to the area being shallower. Figure 4. Temperature measurements from three sampling locations taken in the fall of Water T ( o C) Lower Footbridge Halfway to Upper Footbridge - 9/13/ /4/ /1/ /15/ /6/2015 ph The observed ph of the three sites ranged between about 6 and 8 units with more alkaline conditions seen at the earlier in the fall than in the winter months (when the ph range was between 6.0 and 6.9) but by 11/15/15 the ph dropped to 6.5. Without a ph measurement on 12/6/15 it is difficult to tell whether a ph reading closer to 6.5 would have again been the case. The ph did not vary much between the other two sites during the monitoring period and these fall readings were more in line with the winter ph readings. Figure 5. ph measurements from three sampling locations taken in the fall of ph (ppm) /13/2015 Lower Footbridge Halfway to Upper Footbridge 10/4/ /1/ /15/ /6/

12 Dissolved Oxygen The dissolved oxygen concentrations measured at the three monitoring locations were consistently high, between 9 and 16 parts per million (i.e., mg/l) though not as high as the 18 parts per million readings taken in the winter months. It follows that as temperatures began to drop over the fall monitoring period, biological activity began to subside, creating less of a demand on dissolved oxygen, hence concentrations were observed creeping upward. The water temperature at the was warmer than the other locations at the start of the monitoring period and roughly decreased at each ensuing sampling date - thus an increase in dissolved oxygen concentration was seen over time at this site. Variability occurred at the Lower Footbridge site but halfway to the Upper Footbridge, where temperature had only dropped one degree C at each sampling date (i.e., the water remained warmer), biological activity, hence dissolved oxygen levels, remained the same. Figure 6. Dissolved oxygen from three sampling locations taken in the fall of DO (ppm) /13/2015 Lower Footbridge Halfway to Upper Footbridge 10/4/ /1/ /15/ /6/2015 Nitrogen The predominant nitrogen species present at all three monitoring locations was nitrate-n, which made up most of the Total N concentrations. Ammonium-N concentrations were generally low, and on several occasions, were at or below the detection level of the instrumentation. There appeared to be no clear spatial or temporal trends for ammonium-n. As previously seen in the winter months, nitrate-n and Total N concentrations however, tended to be greatest upstream along Possum Creek and lowest at the site on the Pond. This likely reflects the influence of nitrate-rich groundwater and overland runoff to the tributary. The concentrations generally decrease as the water flows downstream and empties into the Pond. This could be the result of dilution with less nitrate-rich water from other tributaries and overland runoff directly to the Pond itself. With respect to temporal trends, concentrations did not vary much within each of the two upstream sites but generally did at the Pond over time. This was expected for the same reasons as dissolved oxygen changes were explained. On no occasion did the nitrate-n concentration exceed the federal drinking water standard of 10 mg/l. More the case on each of these fall sampling dates than was seen in the winter, the Total N concentrations at both the Lower Footbridge and halfway to the Upper Footbridge sites exceeded the 3.0 mg/l target threshold (blue line) indicating that nitrogen is a concern, and likely most evident during the growing season. 12

13 Figure 7. Dissolved ammonium-n (top), dissolved nitrate-n (center), and Total N (bottom) from three sampling locations in the fall of NH4-N (mg/l) /13/2015 Lower Footbridge Halfway to Upper Footbridge 10/4/ /1/ /15/ /6/2015 NO3-N (mg/l) Lower Footbridge Halfway to Upper Footbridge - 9/13/ /4/ /1/2015 TN (mg/l) 11/15/ /6/ Lower Footbridge Halfway to Upper Footbridge 9/13/ /4/ /1/ /15/ /6/

14 Phosphorus Phosphorus concentrations both total and dissolved were relatively low at the three monitoring locations over the sampling period. Often, levels were at or below the detection limit of the instrumentation and there were no temporal trends, hence the data are not shown. Phosphorus is often attached to sediment particles and enters waterways during and after rain events through overland runoff, but during this fall monitoring period it appears as if there was not enough rainfall per storm event to warrant a noticeable level of phosphorus movement from fields and riparian areas since orthophosphate concentrations were so low. Total P did not exceed the target threshold of mg/l. Project Summary and Conclusions During this last grant period, we collected storm event water samples at two locations along Possum Creek, a tributary to Noxontown Pond, and one location at the Pond, near the confluence of the Creek with the Pond. Possum Creek drains the northwest portion of the Noxontown Pond Watershed and is predominately agriculture in land use. Due to the limited availability of a UD undergraduate student intern, the water quality work did not get underway until September and results only represent fall months. In our May 8, 2015 report, we assessed soil quality data from a field within the agricultural drainage to Possum Creek. Since the soil was rated low in soil health, monitoring was advised as recommendations are made to improve soil health so as to not impact water quality. In the future if cover crops are planted in fields that drain to the Creek and/or Pond then further soil and water assessments can ascertain that what is being done is indeed an agricultural best management practice to preserve both soil and water quality. References Castillo, K., M. Pautler, J. Volk, C. Brownlee, D. Burk, and P. McLean Soil Health and Water Quality at St. Andrew s School, Delaware: Final Project Report. Submitted to GreenWatch Institute, Inc., May 8,