Water Resource System Reporting Key

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This reporting key outlines detailed information about target setting and evaluation of current conditions and trends, including data collection and analysis methodologies, for each of the following Water Resource System indicators:

Aquatic Communities and Habitats

• Fish Communities in Streams
• Benthic Communities in Streams
• Stream Temperature

Groundwater Quantity

• Groundwater Levels

Index of Biotic Integrity

The health of fish communities in streams was evaluated using the Index of Biological Integrity (IBI). Briefly, the IBI score is determined by a combination of fish community characteristics, including species richness, local indicator species, trophic position, fish abundance, and fish condition at a sampling location. Sites are given a score based on criteria about the fish captured at each site according to the following rating scale:

• Very Good: ≥38
• Good: 28–37.9
• Fair: 20–27.9
• Poor: ≤20

Trends for fish communities in streams were assessed by comparing 2001–2010 and 2011–2019 data using a permuted t-test (p<0.05) using 999 permutations conducted using a script from  this website .

Sensitive Species

Redside Dace population status was assessed using the methodology outlined in  Recovery Potential Assessment of Redside Dace (Clinostomus elongatus) in Canada  (DFO, 2019).

Brook Trout populations were evaluated by looking at presence/absence data from TRCA's Regional Fisheries Monitoring Program for recent observations (<20 years) compared to historical observations (>20 years).

Benthic communities were sampled at riffle habitats during the summer using a travelling kick-and-sweep method following established Ontario Benthic Biomonitoring Network protocol as part of TRCA's Regional Watershed Monitoring Program.

Family Biotic Index

The Family Biotic Index is a score based on the tolerance of the macroinvertebrate species present in a stream to common types of pollution. Streams with high water quality will be occupied by pollution-sensitive species and have a lower FBI score.

Hilsenhoff’s Family Biotic Index (FBI) was used to assess stream conditions. The FBI estimates the overall tolerance of the benthic community at each sampling site, weighted by the relative abundance of each taxonomic group. Site scores were calculated as in Hilsenhoff's FBI. The categories (Good, Fair, Poor) were modified from Hilsenhoff's original categories, which included pristine streams in rural and wilderness areas, to best represent the range of conditions within the heavily urbanized Toronto region. The modified categories are as follows:

• Good: 0–5.37
• Fair: 5.37–6.88
• Poor: 6.88–10.00

Trends were determined using a test of statistical significant differences (T-test, p<0.005) for all sites in each watershed between the periods 2001–2010 and 2011–2019.

Sensitive Species

The EPT groups (mayflies, stoneflies, caddisflies) contain many groups that are sensitive to disturbances to stream habitat, and high proportions of EPT are usually found in streams that are less impacted by pollution, flow alteration, or sedimentation among other factors.

Sensitive species were evaluated using the proportion of Ephemeroptera (mayflies), Plecoptera (stoneflies), and Trichoptera (caddisflies) larvae out of the total invertebrate assemblages in riffle habitats. While these are diverse groups whose species vary widely in ecological requirements, many EPT species require clean, cool, well-oxygenated water and relatively un-impacted substrate and flow conditions.

Evaluated using both Regional Watershed Monitoring Program data and other stream temperature data that may not be collected on an ongoing basis. Data are summarized by two Assessment Periods, including 2001–2010 and 2011–2019 to compare data over time

Fluctuations in water level over the period of record have been assigned categories based on extent of the fluctuation in each well, as below:

• Stable water levels: less than 0.1 m
• Slight rise/slight decline: 0.1 to 0.2 m
• Rising/Declining: 0.2 m or greater