Improving Vegetation in the Drawdown Zone at Williston Reservoir

Project Year: 2016-2017

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Williston Reservoir / W.A.C. Bennett Dam

Project Lead

Cooper Beauchesne and Associates Ltd.

Watershed/Sub-region

Peace Region

Parsnip Arm

Project Type

Research & Information Acquisition

FWCP Contribution

$4,920

Action Plan Alignment

Riparian and Wetlands Action Plan

Project ID

PEA-F17-W-1306

Identification of Flood- and Drought-Tolerant Plant Species

Studies on vegetation in the drawdown zone of reservoirs have identified various limiting factors for plant establishment and productivity, including time available for plant establishment prior to flooding, protection from wave action, winter ice and coarse woody debris, as well as the nutrient retention and availability of reservoir substrates. An additional factor that has received less consideration is plant tolerance to drought conditions and flooding. This project aims to identify drought- and flood-tolerant plants naturally colonizing Williston Reservoir, and assess their practicality for seed collection and seedling propagation.

Future work could utilize the results from this study, potentially combined with techniques that address other limitations for revegetation efforts.

Benefits of this work include:

  1. identifying flood- and drought-tolerant native plant species, which could be a useful reference for future revegetation efforts in B.C. interior reservoirs by acting as an important tool for habitat restoration projects;
  2. identifying challenges to seed collection and propagation for identified species (by understanding the limitations to seed collection and nursery propagation (for both identified species and in general), practitioners could avoid wasting time and money when selecting species for restoration efforts); and
  3. identifying preliminary methods for seed collection and propagation for candidate species.

Currently, information on seed collection and propagation of many flood- and drought-tolerant native plant species is limited. This information would again be helpful for future revegetation efforts in B.C. interior reservoirs.

 


Final Report: Executive Summary

Fluctuations in water levels of the Williston reservoir as a result of seasonal variability in water inflow and outflow create a zone of continuous changes in area and depth of flooding along its shoreline, defined as the drawdown zone. Within this zone, growing conditions for terrestrial and aquatic vegetation are challenging and often highly inhospitable requiring plant species that can survive both drought like conditions and often extended inundation as well as in impoverished soils. Efforts by BC Hydro to establish or enhance existing vegetation cover in upper portions of the drawdown zone of reservoirs in British Columbia (BC) have tested a variety of species, both native and non-native. Species employed have
included agronomic and native, wetland graminoids and native tree and shrub species.

The initial stage of this project outline in this report had two objectives. The first objective was to identify candidate flood and drought tolerant native plant species for use in the revegetation of the upper drawdown zone in the Williston Reservoir. Candidate species were selected from a comprehensive list of plant species known to naturally colonize the drawdown zone. The second was to assess the potential to collect seed and propagate seedlings for each of the candidate species. Identifying candidate species and assessing the potential for seed collection and propagation was conducted using relevant literature and discussions with native plant seed collectors and propagation experts, revegetation specialists and local First Nations. These objectives have been developed to support action 2a-1of BC Hydro’s Peace Basin Riparian and Wetlands Action Plan, which aims to identify flood and drought resistant plant species for bank stabilization.

Click the provincial database link below to read the full final report for this project.

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