North Saskatchewan River

Intro: In Canada, Giardia and Cryptosporidium are the main etiologic agents of waterborne outbreaks and related illness. It has been predicted that climate change will lead to rises in temperature and increases in severity and frequency of rainfall events and droughts. Therefore, it is important to understand the impacts of these variables on the presence and distribution of Cryptosporidium and Giardia in raw water sources. 
Objective: The objective of this study is to: a) compare the distribution of Cryptosporidium and Giardia at two sites on the North Saskatchewan River - intakes of E.L. Smith and Rossdale Water Treatment Plants in Edmonton- between 2012 and 2014 (n=21); b) determine if various chemical, physical or biological water quality variables are significantly correlated with Cryptosporidium and Giardia presence in surface water; and c)construct a multivariate regression model to predict presence of Cryptosporidium and Giardia in the North Saskatchewan River when possible.
Methods: The enumeration of Cryptosporidium and Giardia was performed using US EPA Method 1623. The collection of physical and chemical water quality variables was performed using Standard Methods, while climactic data was collected from the Environment Canada site. Correlations were determined using Spearman correlations and other non-parametric statistical tests.
Results: Results indicate that there was no statistically significant difference between concentrations of Cryptosporidium at the two plant intakes (p =0.06), but there was a statistically significant difference for Giardia concentrations (p = 0.03). Mean number of Cryptosporidium and Giardia at the Rossdale water treatment plant were 6.73 ± 1.09 and 40.00 ±7.42, respectively. Mean number of Cryptosporidium and Giardia at the E. L. Smith water treatment plant were 9.88 ± 2.24 and 33.78 ± 8.94, respectively. The results also show a clear seasonal trend, with protozoan concentrations being highest in the summer time in both years (June-August). Spearman correlations showed a strong positive correlation between Cryptosporidium and Giardia numbers at each site (Rossdale p = <0.0001; Smith p = 0.008). Temperature was positively correlated with both Cryptosporidium and Giardia at both sites with p-values < 0.007. While rainfall and turbidity showed no relationships with Cryptosporidium or Giardia at Rossdale, turbidity showed a strong trend with Cryptosporidium concentrations but not Giardia at EL Smith (p <0.0001). Total coliforms correlated with Cryptosporidium (p = 0.0010) and E. coli (p = 0.0103) at Rossdale but neither correlated with Giardia, and the same trend was not observed at EL Smith. Finally, there was a negative statistically significant relationship between nitrate and Cryptosporidium and Giardia concentrations at both sites, which was much stronger with Giardia than with Cryptosporidium.         
Relevance: Understanding the prevalence of pathogens in natural ecosystems and the factors that impact their distribution are important factors in development of sound management strategies that limit risk and protect public health. This study elucidates different relationships between potentially pathogenic protozoa and various commonly-monitored water quality variables that could aid in monitoring and predicting source water quality.