CLIMATE, FLOW SOURCE, AND NUTRIENTS IMPACT PHYTOPLANKTON BIOMASS IN A HYDROLOGICALLY MANAGED, SHALLOW DRINKING WATER RESERVOIR

Climate and human activities play important roles in driving phytoplankton biomass, which can strongly impact drinking water treatment, especially in shallow lakes where biomass is often both high and highly variable. We present a study that used ~40 years of data and generalized additive models to assess the factors influencing changes in chlorophyll a concentrations in a shallow reservoir that serves as a major drinking water source in Saskatchewan, Canada. We show that between 1992 and 1997, chlorophyll a levels rose significantly, coinciding with increased precipitation and catchment inflows, along with intermittent warm, dry periods linked to El Niño events—all which had considerable effects on nutrient dynamics and algal growth. Our findings demonstrate that nutrients, climate, and hydrological management are key predictors of chlorophyll a variability, with flow releases from the mesotrophic upstream reservoir having a beneficial effect by reducing algal biomass. Managing flow releases from upstream reservoirs and nutrient export from the watershed are important strategies to lower drinking water treatment costs in shallow, hydrologically managed reservoirs.

Presentation Preference: Oral

Primary Presenter: Danielle Spence, University Of Saskatchewan (danielle.spence@usask.ca)

Authors:

Danielle Spence, University of Saskatchewan  (danielle.spence@usask.ca)

Kristin Painter, University of Saskatchewan  (kristin.painter@usask.ca)

Jason Venkiteswaran, Wilfrid Laurier University  (jvenkiteswaran@wlu.ca)

Helen Baulch, University of Saskatchewan  (helen.baulch@usask.ca)