A Management Challenge:

Transcription

1 A Management Challenge: Water Quality in Stormwater/ Homeowners Association Ponds Eugene Braig, Program Director, Aquatic Ecosystems OSU Extension, School of Environment and Natural Resources

2 Some practical pond-management references Austin, M. et al Pond management handbook: a guide to managing ponds for fishing and attracting wildlife. Ohio Department of Natural Resources, Division of Wildlife, Columbus, OH. Once available in its glorious entirety from a nicely organized and information-rich ODNR web site. Currently out of print and unavailable in any format. Many Ohio pond-management fact sheets available under Natural Resources at: Occasional articles posted to

3 A Management Challenge: Water Quality in Stormwater Ponds The Outline: The nature of the challenge Stratification as a nutrient source Management considerations Stratification Vegetation Optional fisheries

4 A Management Challenge: Water Quality in Stormwater Ponds The Outline: The nature of the challenge Stratification as a nutrient source Management considerations Stratification Vegetation Optional fisheries

5 Stormwater Ponds: The Challenge Watersheds usually thoroughly developed. Often large proportions of impervious surface. Often heavily fertilized. Basin designed to absorb problem pollutants (sedimentation, excessive nutrients, contaminants, etc.) from the landscape before they can enter natural surface waters. Wet extended detention pond (Ohio Department of Natural Resources 2014)

6 Stormwater Ponds: The Challenge Foxwood Villas (City of Toledo Engineering Services 2015) Excessive sedimentation: Functionally ages a pond. Prematurely reduces pond volume and thus capacity for storage. Becomes a nutrient and contaminant sink; can be released to the water column in low-oxygen conditions. Will require periodic dredging.

7 Stormwater Ponds: The Challenge Excessive nutrient loading: Functionally ages a pond. Can promote nuisance coverages of otherwise beneficial submerged vegetation. Can fuel the growth of nuisance organisms: e.g., duckweeds, filamentous algae, or potentially toxic harmful algal blooms. Excessive growth of green things can lead to wide oxygen fluctuations. A homeowners association lake in Geauga Co. with some substantial nutrient issues (Keith Anderson 2014)

8 Successful pond management Nutrient management In freshwater aquatic systems, phosphorus (P), tends to be rare and thus is the primary limiting nutrient. Little phosphorus = few problems.

9 A Management Challenge: Water Quality in Stormwater Ponds The Outline: The nature of the challenge Stratification as a nutrient source Management considerations Stratification Vegetation Optional fisheries

10 Limnology 101: Stratification basics The hypothetical pond-basin schematic:

11 Limnology 101: Stratification basics Spring turnover (mixed): Wind 39 F 39 F 39 F 39 F 39 F 39 F 39 F

12 Limnology 101: Stratification basics Pop quiz! Which is denser/ heavier : warm or cold water? For the most part, water s density increases (water gets heavier ) with decreasing temperature. The most important temperature in the world: However, water is densest at approx. 39 F, density again decreasing as temperature falls below that level. This fact makes life possible. Why? Freezing at 32 F, ice is less dense than cold water and floats rather than freezing from the bottom up.

13 Limnology 101: Stratification basics Late spring (initial stratification): Wind Epilimnion Thermocline Hypolimnion 60 F 60 F 58 F 54 F 50 F 46 F 46 F

14 Limnology 101: Stratification basics Summer (strongly stratified): Wind Epilimnion Thermocline Hypolimnion 76 F 76 F 64 F 54 F 50 F 46 F 46 F

15 Limnology 101: Stratification basics Fall turnover (mixed): Wind 50 F 50 F 50 F 50 F 50 F 50 F 50 F

16 Limnology 101: Stratification basics Winter (stratified): Ice cover 32 F 34 F 36 F 38 F 39 F 39 F 39 F

17 Limnology 101: Stratification basics Factors affecting stratification: Pond depth: Likelihood or strength of stratification increases with depth. Shallow ponds (perhaps < 8 feet) may not stratify or may only stratify occasionally and briefly. Deeper ponds (perhaps > 12 feet) almost always stratify.

18 Limnology 101: Stratification basics Factors affecting stratification: Wind: Stratification delayed, thermocline driven deeper, or seasonal mixing initiated earlier with increasing wind energy. Orientation of fetch (i.e., the length of open water across which wind can build up) to prevailing winds influences wind energy imparted to pond. Even deep ponds (perhaps to 16 feet) may not stratify if fully open to regular, strong winds. Even very shallow ponds are likely to stratify every season if strongly sheltered.

19 Limnology 101: Stratification basics Factors affecting stratification: Weather. During calm, hot summers, the interaction of temperature and lack of wind lead almost all ponds (even if very shallow) to stratify. Premature/Early turnover: Sudden, cold rainfall with late summer storms can chill epilimnetic water, increasing density and forcing it deeper into the water column, thus displacing and driving up hypolimnetic water. Symptom is often dark grayish or blackish cloudiness of pond water as organic muck/sediment is stirred up with movement of bottom water.

20 Internal sources of excessive P ( where DO is dissolved oxygen) Kalff, J Limnology: Inland water ecosystems. Prentice Hall, Upper Saddle River, NJ.

21 The vicious cycle (of P, that is) Low hypolimnetic oxygen renders P in sediments more soluble. Decomposition consumes oxygen in hypolimnion. Your Pond As algae die off, they settle into pond sediments, and decompose. P released to water column fuels algal blooms.

22 A Management Challenge: Water Quality in Stormwater Ponds The Outline: The nature of the challenge Stratification as a nutrient source Management considerations Stratification Vegetation Optional fisheries

23 Basic management considerations These sites are human-made and intensively managed, so consider managing to deliberately and sustainably best serve the site s intended goals and objectives, even where management might differ from natural system function. The site s primary function retention of water and pollutants must take priority if it conflicts with other intended uses. Supplemental management actions should reflect compromise to at least partially recognize the expectations of each user/owner/stakeholder. Some peripheral specifics: If at all possible, exclude Canada Geese from site! Only use herbicides specifically labeled for aquatic applications and strictly follow label recommendations!

24 Basic management considerations Keep lawn waste out of ponds. Fertilize conservatively with phosphorus-free fertilizers. Mow lawns as tall as possible to promote root growth. Do not over-water (1 2 inches/week total). Discharge downspouts to lawns rather than impervious surfaces. Maintain native plants in landscape.* Plant rain gardens. Maintain ft-wide vegetated buffer strips around ponds.* Pick up trash and pet waste before entering ponds or storm sewers. Do not dump household or automotive chemicals in yards or storm drains. The Stormwater Coalition of the Toledo Metropolitan Area Council of Governments (May 2015) * Some emergent/shoreline species recommendations provided by Ohio Department of Natural Resources (ODNR 2014).

25 Basic management considerations ODNR Rainwater and land development: Ohio s standards for stormwater management, land development and urban stream protection, 3 rd edition. ODNR Division of Soil and Water Conservation, Columbus.

26 Planning for construction Design ponds following ODNR (2014) guidelines for storage capacity and managing sediment loads. Especially if considering a fishery, at least 25% of the main basin 12-ft deep in the north of Ohio; 8-ft deep elsewhere in the state (Austin et al and differs slightly from ODNR 2014). If possible, align fetch of pond to take advantage of prevailing winds. Plan landscaping to again to take advantage of prevailing winds; plan trees along eastern/ northeastern shores (here, I differ slightly from ODNR 2014).

27 A Management Challenge: Water Quality in Stormwater Ponds The Outline: The nature of the challenge Stratification as a nutrient source Management considerations Stratification Vegetation Optional fisheries

28 Not all aerators are created equal! Minimal nutrient-management benefits (but is potentially useful to introduce dissolved oxygen directly and it is kinda pretty) Maximum nutrient-management benefits: Cheaper, efficient, and effective

29 Not all aerators are created equal! Kalff, J Limnology: Inland water ecosystems. Prentice Hall, Upper Saddle River, NJ.

30 Why aerate? Specifically, regarding moderately coarsebubble/pneumatic diffusers: Bubbles themselves directly introduce some oxygen, but contribution tends to be negligible. The finer/smaller the bubble, the greater the surface area of bubbles en masse and the more oxygen directly introduced. Coarser bubbles driving up from the bottom tend to drag water mass with them, creating circulation and disrupting stratification. While very fine bubbles introduce more oxygen directly, they cannot move enough water to disrupt stratification. Without the physical barrier imposed by dense hypolimnion, atmospheric oxygen is potentially able to penetrate to bottom waters, potentially eliminating anoxia in the hypolimnion.

31 Why aerate? Oxygenating bottom sediments: Enhances production and efficiency of aerobic bacteria, thereby increasing efficient decomposition (slowing the accumulation of organic muck) and shifting the nitrogen cycle towards harmless nitrate. Reduces possibility of summer and winter fish kills. Reduces or eliminates internal cycling of phosphorus. Circulating water mass: Circulates and suspends nutrients for rapid uptake into the planktonic food web. Reduces nuisance algae and duckweed abundance through rapid nutrient uptake by planktonic algae (fueling beneficial food webs).

32 Why aerate? How many? Ideally, 2 3 diffusers per acre positioned along deep water. How much? Estimate pond volume: i.e., surface area x average depth. Check manufacturer specs: Recommendation range: hours for one complete turnover of pond volume. Relatively common objective: turn over pond volume twice per day (i.e., 12 hours/turnover).

33 Shall we begin? Implement any aeration program (and, really, any large-scale change in management) when waters are cool, namely in the spring. Disrupting waters that have already strongly stratified for the season paradoxically, even via aeration has the potential to bring hypoxic/ anoxic water to the surface, causing premature turnover, oxygen crash, and a summer fish kill. Ideally, fire up system in the spring, run all day every day throughout warm months, and shut down in autumn.

34 A Management Challenge: Water Quality in Stormwater Ponds The Outline: The nature of the challenge Stratification as a nutrient source Management considerations Stratification Vegetation Optional fisheries

35 Submerged aquatic vegetation Westlake (Eugene Braig 2015) Tolerating the right coverage by a diverse assemblage is good for water quality and fishes, perhaps: 5 20% of the site s area for managing fisheries. As much as 30% for functions where fisheries aren t a consideration. Maintaining the right coverage will likely require a commitment to active management.

36 Submerged aquatic vegetation Westlake (Eugene Braig 2015) The right coverage provides: Nutrient storage: beneficial competition against serious nuisance organisms (like toxic blue-green algae, filamentous algae, and duckweeds). A more stable source of dissolved oxygen than planktonic algae can. Habitat for forage and cover to balance predator prey fish interactions.

37 Plant-management options Dyes. Mechanical removal. Grass Carp/White Amur. Herbicide/Algaecide applications.

38 A few words on herbicide use To limit liability concerns, private individuals should not apply herbicides to homeowners association sites; only licensed applicators should (Ohio pesticide applicator certification category 3a). Only use chemicals labeled for aquatic applications, very strictly adhering to all label requirements for application, safety, and storage. Identify the algae/plant correctly, and select a product likely to be effective. Consider any water-use restrictions associated with selected product (listed on label). Differentiate between treatment strategies: Whole-water treatment: early growing season and cool water only to calculated volume of pond water. Spot treatment: selective by area including for limited warmer season treatments. Differentiate between contact and systemic herbicides. Feel free to contact me for resources as necessary.

39 Aquatic herbicide chemical Name Absorption Selectivity Water-Use Restrictions Copper (copper sulfate and copper chelates) Contact Broad Minimal Sodium carbonate peroxyhydrate Contact Broad Minimal Diquat Contact Broad Moderate Flumioxazin* Contact Broad Moderate Carfentrazone-ethyl* Contact Broad Moderate Endothall (amine salt and potassium salt) Contact Broad Moderate Glyphosate Systemic Broad Minimal Imazamox Systemic Broad Moderate Fluridone Systemic Selective Moderate Penoxsulam* Systemic Selective Moderate Bispyribac* Systemic Selective Extended Imazapyr Systemic Selective Extended Triclopyr Systemic Selective Extended 2,4-D Systemic Selective Extended For details, see OSU fact sheet Chemical Control of Aquatic Plants (excepting *).

40 Contact Herbicide Control (not limited to ) Copper sulfate and copper chelates (a vast many: e.g., Cutrine brands, etc.): mostly algae (some submersed). Sodium carbonate peroxyhydrate (e.g., GreenClean, Pak 27, Phycomycin, etc.): near-surface and shallow algae. Diquat (e.g., Reward, Weedtrine-D, Aquastrike [Endothall-dipotassium blend], etc.): submersed plants and some filamentous algae. Flumioxazin* (e.g., Clipper): misc. submersed and free-floating plants, especially duckweeds and watermeal. Carfentrazone-ethyl* (e.g., Stingray): misc. floating and emergent plants. Endothall (e.g., Aquathol, Hydrothol, Evac Biocide, Aquastrike [Diquat blend]): submersed plants and algae. Karmex*/Diuron*, etc.: Do not use! Not labeled for aquatic applications. For details, see OSU fact sheet Chemical Control of Aquatic Plants (excepting *).

41 Systemic Herbicide Control (not limited to ) Glyphosate (e.g., Rodeo, Aquamaster, AquaPro, Eraser AQ, etc.): emergent plants. Imazamox (e.g., Clearcast): very broad effectiveness, including several submersed invasives. Fluridone (e.g., Sonar, Avast, Whitecap, etc.): primarily submersed and free-floating plants. Penoxsulam* (e.g., Galleon): emergent and some floating weeds including on exposed pond sediments. Bispyribac* (e.g., Tradewind): misc., esp. floating and submersed. Imazapyr (e.g., Habitat, Arsenal, etc.): emergent (esp. grasses) & some floating weeds. 2,4-D (e.g., AquaKleen, Navigate, Aquacide, Sculpin G, Weedar 64, etc.): specific plant species such as Eurasian watermilfoil, coontail, and limited effectiveness on waterlilies. Triclopyr (e.g., Renovate, Garlon 3A, Navitrol, etc.): selective effectiveness similar to 2,4-D. For details, see OSU fact sheet Chemical Control of Aquatic Plants (excepting *).

42 Managing aquatic plants Filamentous algae: Vascular plants: (general) (cattails) (duckweeds and watermeal) Grass Carp:

43 A Management Challenge: Water Quality in Stormwater Ponds The Outline: The nature of the challenge Stratification as a nutrient source Management considerations Stratification Vegetation Optional fisheries

44 Pond fisheries The nature of smallness: limited space and lack of habitat diversity. A pond cannot function like Lake Erie in supporting a fishery! Keep fisheries extremely simple! Usually a single level of predator prey interaction. Largemouth Bass Bluegill (supplementing with Channel Catfish if desired) is our region s tried and true. A Delaware Co. pond (Steve Collignon 2014)

45 Questions?

46 A Management Challenge: Water Quality in Stormwater Ponds Eugene Braig, Program Director, Aquatic Ecosystems