Headwater Study

Ecologists are concerned that anthropogenic changes, such as urbanization, in headwater areas can cause degradation in downstream aquatic systems. However, the process of this degradation and how it relates to the natural functions of headwater drainage features is poorly understood and likely underestimated. TRCA, in collaboration with many partners across Southern Ontario, has undertaken a series of studies to better understand these natural functions and begin to address some of the gaps in the science.

It's finally here! There is a new version of the headwater guideline and it is ready for your comments. We have made great improvements to the document, including:

1. Overhaul of the evaluation section to include connections to the new headwater sampling protocol, which is now a new module in the Ontario Stream Assessment Protocol (OSAP).
2. The evaluation section has also been modified to allow sampling to be scoped based on important criteria, such as feature sensitivity, flow and form, and proposed alteration.
3. The classification system now takes the data that were collected through the evaluation and classifies features according to hydrology, riparian condition, and if negative alterations are proposed, fish and fish habitat, and terrestrial habitat. All factors are classified using the same categories: important, valued, contributing and limited functions.
4. We have added a flow chart that helps to link the classification to the recommended management.
5. The management section now provides very specific direction on when a management recommendation applies. There is also some direction provided to possible restoration options.

There is a 30-day commenting period, so please click here to provide your comments before May 10!

Since 2006, TRCA and partners have been undertaking a series of studies to better understand the natural functions of headwater drainage features. Headwater drainage features are small, temporary streams, swales and wetlands. These studies were undertaken by the study team because agencies and scientists are beginning to recognize that the natural functions associated with headwater drainage features are poorly understood and underestimated. While the functions of perennial headwater streams are fairly well accepted, temporary systems that may flow for only parts of the year are virtually unstudied and unmonitored. Their small size and the fact that they do not necessarily flow year-round, makes them particularly vulnerable to impacts such as piping, channelization, flow diversion, grade lowering and realignment. However, there is a growing body of evidence to suggest that headwater drainage features are important sources of food, sediment, nutrients, and flow to downstream aquatic systems, and they also provide water quality, storage and attenuation functions as well.

Improving our understanding of these systems is critical, and the timing for developing land use policies and guidelines for protecting headwater functions is now. The Greater Toronto Area and surrounding municipalities are expected to grow by 2 million additional people over the next 20 to 25 years. Much of this growth could be concentrated towards the upper reaches of our watersheds where the concentration of headwater drainage features is higher. This growth has the potential to have substantial impacts on our watersheds, hence it is essential that we understand the functions of headwater drainage features such that we can properly protect these important functions.

The following reports, guidelines and presentations are the up-to-date results of TRCA's Headwater Study.

Comments

We have updated the Headwater Guideline, and we want to hear from you!

• Evaluation, Classification and Management of Headwater Drainage Features: revised April 2013 - 658K

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