Approach
This approach addresses scenarios in which wetlands may experience larger footprints of saturation and higher water levels for longer periods of time due to increased precipitation. Wetlands may also experience inundation outside the normal wet season, such as in late summer due to extreme precipitation events. Water levels may remain high for a prolonged length of time following extreme precipitation in small isolated wetlands, in wetlands downstream of managed lakes and rivers due to continued upstream water release, and in groundwater wetlands in areas underlain by shallow unconfined aquifers. In riparian systems, higher flows may also lead to greater scouring and spread invasive species propagules; and yet more frequent higher water levels can interfere with the normal low-water cycle of germination and establishment of new seedlings. These hydrologic shifts will drive changes in the plant community and other wetland ecosystem parameters linked with desirable functions (e.g., biodiversity, nutrient retention and cycling). Managers can help systems adapt by working to maintain desirable functions, such as planting species that are tolerant of anticipated hydrologic changes. Systems with impoundments may necessitate special attention to reduce the adverse impacts of prolonged higher water levels while continuing to provide ecosystem services.
Tactics
- Control the encroachment of undesirable species that respond to higher water levels (e.g., pickerel weed (Pontederia cordata) in wild rice beds, non-native cat-tails (e.g., Typha angustifolia, T. x glauca), Phragmites australis var. australis.
- Encourage seeding or planting of wetland plant species adapted to high water levels (e.g., with a wetland rating of OBL).
- Install carp barriers to anticipate increased invasion with flooding and higher water levels.
- Promote non-invasive plant species in riparian wetlands with adaptations to tolerate alternating heavy flooding with lower baseflows. FACW and FAC wetland plant species are adapted to a broader range of hydrologic conditions than OBL wetland species.
- In riparian systems influenced by an upstream hydroelectric dam, manage dam releases to mimic natural flow regimes to improve germination and establishment of plant species.
- In impoundments and lakeshores with a steep side slope, supplement wave-reducing measures by installing substrate support agents such as biodegradable geotextiles.
- Maintain a lower summer water level in impoundments and lakes managed by a dam to increase storage capacity of extreme precipitation events and reduce downstream flooding impacts.
- Where concentrated flow enters a wetland, such as at a culvert or a storm sewer outfall, install energy dissipation features to limit negative impacts of extreme runoff events on wetlands.
Strategy
Strategy Text
This strategy outlines approaches to facilitate ecosystem adjustments to cope with altered hydrology, water budget components (inputs, outputs, and storage of water) and water quality. Managers face both challenges and opportunities from a periodic lack of water (e.g., from drought and higher evaporation) as well as excess water (e.g., from larger precipitation events) that go beyond the historical range of variation in both magnitude and duration. Wetland managers will therefore need to adjust systems to maximize desirable ecosystem functions despite altered hydrology. This adjustment includes all components of wetland systems such as flood storage capacity, site nutrient cycling, as well as the habitat suitability of plants, wildlife, and aquatic species. Adjusting wetland ecosystems to climate changes applies equally to natural areas, as it does to wetland creations and enhancements, and existing hydrologically managed systems (e.g., lakes, impoundments, and rivers regulated by dams and other hard infrastructure). Proactive consideration of hydrologic change can help managers reduce future risks and take advantage of opportunities to sustain hydrologic functions into the future.