The ecological implications of altering the hydrologic regime, or hydroperiod, of
a wetland system include major changes to both ecosystem structure and function.
Wetland systems are generally sinks of nutrients such as phosphorus, nitrogen and
carbon, which are important to water quality. Changes in the hydroperiod such as the inundation or drainage of a wetland system alter wetland function and may switch
the system from functioning as a nutrient sink to a source.
In this study, I explored the effects from the introduction of a seasonal inundation
regime to the Begbie Lake wetland system. Begbie Lake is hydrologically connected
to the Sooke Lake reservoir, the main drinking water supply for Greater Victoria,
British Columbia. In 2002, the dam on the Sooke Lake reservoir was raised by 6
m, which led to the seasonal inundation of the Begbie Lake wetland system in 2005
and 2006. In 2005, the Begbie Lake wetland system was inundated for 57 days, from
April through May. In 2006, the wetland was inundated for 123 days, from January
through May. The seasonal inundation resulted in the release of phosphorus, nitrogen and carbon from the wetland system into Begbie Lake and the Sooke Lake reservoir.
Nutrients such as phosphorus and nitrogen are especially important in drinking water
reservoirs, where increases in concentrations often lead to increased algal biomass and possibly a shift toward cyanobacteria-dominated phytoplankton communities. Organic carbon in source water is correlated with disinfection by-product production during treatment, increases in bacterial biomass within distribution systems, and decreases in the efficacy of water treatment.
The response to inundation of the wetland system, in terms of the release of key
water quality nutrients into Begbie Lake was assessed. Water chemistry data collected
from 2005 and 2006 were compared to pre-inundation baseline data (2003 and 2004)
over the growing season. Phosphorus, nitrogen and organic carbon concentrations
above the flooded wetland soils increased significantly during the inundation periods.
Following drawdown, the total phosphorus concentration in Begbie Lake increased
signi cantly. Total nitrogen and total organic carbon concentrations in Begbie Lake
did not increase over this same period; the microbial mineralization and reduction of
nitrogen and organic carbon, as well as the export of these nutrients into the Sooke
Lake reservoir, are proposed as in
uencing the observations.
The inundation of the Begbie Lake wetland system also resulted in the export of large amounts of nitrogen and organic carbon to the Sooke Lake reservoir. The increase in the duration and extent of inundation in 2006 resulted in higher contributions from the Begbie Lake wetland system. The export of nitrogen increased from 3.8 kg in 2005 to 4.4 kg in 2006. Carbon export increased from 77.7 kg in 2005 to 171.1 kg in 2006. The export of high amounts of phosphorus were not observed during the study. While phosphorus concentrations increased above wetland soils, the data suggest that much of the phosphorus remained cycling within Begbie Lake.
| Identifer | oai:union.ndltd.org:uvic.ca/oai:dspace.library.uvic.ca:1828/3118 |
| Date | 16 November 2010 |
| Creators | Sinclair, Jesse |
| Contributors | Mazumder, Asit |
| Source Sets | University of Victoria |
| Language | English, English |
| Detected Language | English |
| Type | Thesis |
| Rights | Available to the World Wide Web |
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