Notable Improvement in Water Quality – What a Pond Assessment Before and After PondHawk Installation Revealed
Author(s): LINNE Industries primary research
Summary: In this edition of BRIEFS, we deliver the results from our own PondHawk field research. We collected water quality data from the ponds of one of our repeat customers, a Midwest municipal golf course. The course has installed 15 PondHawk systems – five per year since 2018.
In August 2020, LINNE Industries learned that this client had procured a comprehensive assessment of their golf course ponds in 2018, just a few months before installing their first five PondHawk systems. The objective of their research was to understand the baseline conditions and provide best management solutions for the development of an operations and maintenance plan. The baseline data was collected and analyzed by STONE Environmental Engineering & Science, Inc. (STONE) and included measuring temperature, total phosphorus and nitrogen, dissolved oxygen, ammonia, nitrite, nitrate, pH, turbidity, conductivity, sediment buildup, and observational data.
Key Takeaways
- PondHawk has delivered notable improvement in dissolved oxygen (DO) levels and destratification of temperature throughout the water column.
- Bubblers and diffused aerators are more proficient at adding oxygen to the entire water column than surface aerators.
- Using solar aeration allows for the systems to be installed throughout the golf course without disruption to the existing infrastructure.
- The report summarizing the 2018 assessment by STONE presented several potential management solutions, including installing subsurface aerators as a long-term, low cost tool to mitigate pond stratification and improve DO concentration throughout the entire water column. Other pond management tools include: community education, nutrient management, natural buffers, dredging, littoral shelves, and chemical, dye, and biological treatments.
The Study
Motivation for Original Assessment
The client had concerns with aesthetics, water quality, and the functionality of its stormwater ponds. Pond aesthetics were deteriorating due to excessive algae growth, and buildup was beginning to impair stormwater management capability.
The golf course ponds are in an EPA-designated impaired watershed that covers an area approximately 48 square miles (30,720 acres). In the watershed, 78% of the land is developed, 15% is in row crops, 4% is forested, 2% is grass/pasture, and 1% is “other.” The golf course maintains 50 acres of fairways, 18 acres of rough, five acres of greens, and six acres of driving range around 34 acres of water. While designated buffer areas are not mowed, golf carts frequently drive through buffer areas as an alternative path when paved cart paths are intermittently blocked. The golf course employs best management practices in mowing height and frequency, but the observational research found that the residents surrounding the golf course mow grassy buffers to the shoreline, employ haphazard lawn fertilization, and feed the wildlife.
STONE’s Recommendations
In addition to citing subsurface aeration as a potential management solution as a long-term, low cost tool, STONE recommended a range of best management practices including community education on mowing habits and ending wildlife feeding, increasing buffer widths, adding littoral shelves and forebays, chemical and biological treatments, and examining the feasibility of dredging.
What LINNE Replicated
With the valuable baseline data that was collected before the PondHawk installations, LINNE Industries sought to measure the changes after two years of PondHawk aeration. We deployed an Aqua-Troll 500 multiparameter sonde to collect temperature, pH, conductivity, turbidity, and DO levels at various locations and compared the parameters with those documented in 2018.
Our comparative assessment focused on the pond that originates at Hole 14 and drains into the pond on Hole 15. These ponds are part of an interconnected series that act as a filter before the water exits the property and drains into a nearby stream. The pond is directly adjacent to areas of recent or active construction and collects run-off from an agricultural field, giving it a regular source of nutrients and sediments.
From the boat with the Aqua-Troll 500 multiparameter sonde, LINNE industries collected samples from 151 locations across the pond at 1, 2, 4 and 6’ depths.
A Boost in Dissolved Oxygen
Low DO levels are unable to support aquatic life and lead to anoxic conditions in the bottom sediment. The anoxic condition allows an internal nutrient-loading process by re-released nutrients that were formerly bound to the sediments. Pond stratification can also lead to low DO when a barrier or thermocline prevents mixing oxygen-rich surface water with the deeper water that is low in DO. By adding subsurface aeration, the thermocline is disrupted, and oxygen-rich surface water is circulated throughout the water column while reducing temperature stratification that can lead to “turnover” in the water that is harmful to aquatic life.
The Best Management Practices Planning Guide, by the United States Golf Association and the Golf Course Superintendents Association of America, recommends DO levels above 2 mg/L to prevent fish kills. The United States Geological Survey recommends that DO levels be a minimum of 5.0 mg/L.
The 2018 baseline sampling of Pond 15 measured the DO of 0.45 mg/L at 6 feet. The sample at 6 feet in 2020 was up to 6.27 mg/L at the same 6’-deep location, an improvement of 5.82 mg/L at 6 feet.
Other Results
The temperature samples from 2018 indicated higher water temperatures at 2 feet of depth and lower temperatures at 6 feet of depth. In 2020, the Aqua-Troll monitor readings found reduced temperature stratification with lower surface temperatures and higher bottom temperatures than the baseline values. When subsurface aeration was added to the pond, the colder water at the bottom was mixed with the warmer surface water and circulated throughout the water column, eliminating the thermocline barrier.
Turbidity levels at 2- and 6-foot depths also improved since 2018. Reduction in turbidity is indicative of reduced suspended sediment and/or plant material in the water column. The recommended range is 1 – 50 NTU[i]. In the baseline study, turbidity measured 11 NTU and 231 NTU at 2 and 6 depths, respectively. The samples taken in 2020 measured turbidity at 1.29 NTU and 5.51 NTU at 2- and 6-feet depths, indicating a reduction in suspending matter in the water column.
While the conductivity of the 2018 water samples were within the goal range (100-800 µS/cm is considered acceptable with readings less than 600 µS/cm considered optimal[ii]), the 2020 samples ticked down slightly, indicating reduced pollution or dissolved material in the water column.
Conclusion
As STONE noted in their 2019 report, the golf course observed a “large aesthetic improvement within one week” of PondHawk installation. The client continues to incrementally add PondHawk aeration systems every year. Pond aesthetics are important to community wellbeing, but improving the pond water quality before it moves downstream is the real objective. LINNE Industries recognizes that water sampling is a snapshot in time and conditions that influence values can fluctuate hourly, daily, and seasonally. Nutrients and sediment from the watershed, detritus from trees, algae blooms, and aquatic plants, rain or lack of rain, and wind or lack of wind can all instantaneously change the water conditions. With these variables in mind, LINNE Industries continues to conduct primary water quality research and create innovative product developments that improve water quality in stormwater, golf course, and community ponds.
[i] Nephelometric Turbidity Units
[ii] microSiemens per centimeter
View a similar article in the Philadelphia Golf Course Superintendents Association’s newsletter The Bonnie Greensward page 21.
