The overarching goal of Theme 2 is to develop a framework for the use of the sediment fingerprinting technique, supplemented by other approaches such as land use and river channel mapping and sediment quality assessment, to identify the role of key watersheds dominated by specific land uses (i.e. agriculture and forestry) and disturbances (e.g., wildfires) in supplying fine-grained sediment to the Nechako main stem. The work builds on the finding of the Phase 1 project by investigating the importance of specific sources and developing new fingerprinting properties. This information will provide the scientific basis for improved understanding of sediment sources and transfers, thereby helping to protect sensitive aquatic habitats and ecosystems from sediment and its associated contaminants.
The objectives of Phase 2 of the sediment fingerprinting are as follows:
1. To use compound-specific stable isotopes as sediment fingerprints to investigate the contribution of sediment from different land cover types (e.g. forest vs agricultural crops vs pasture) to the sediment load delivered to the Nechako main stem;
2. To use persistent organic pollutants (POPs, e.g. PAHs, PCBs, legacy pesticides) to identify the contribution of specific agricultural practices and areas impacted by forest disturbance (i.e sampling within Shovel Lake wildfire) to the sediment load delivered to the Nechako main stem;
3. To further assess (i.e. extend results from Phase 1 project) the quality of the sediment delivered to the Nechako main stem in terms of POPs and heavy metals;
Although unplanned at the outset of the project, the fires in the summer of 2018 have provided interesting opportunities to Theme 2’s project (Figure 1). We are hoping to conduct experiments to determine what kind of precipitation events and/or intensities will generate runoff that can carry burned sediments into nearby streams; and
4. To provide guidance on the likely roles of projected changes in land use, watershed management and climate change on sediment sources in the Nechako River Basin.
Figure 1. Kristen Kieta, PhD student, taking soil samples near Ormund Creek within the Shovel Lake fire.