Abstract
Herbicide use varies both spatially and temporally within managed forests. While information exists on the effects of herbicide use on water quality at the site and small catchment scale, little is known about the cumulative effects of herbicide use at the landscape scale. A cumulative effects analysis was conducted in the upper Rangitaiki catchment (118,345 ha) in New Zealand, to determine the risk to water quality from two herbicides commonly used for post-plant weed control: terbuthylazine and hexazinone. Data from a 12.5 ha catchment study within the Rangitaiki Basin, where these herbicides were aerially applied in two consecutive years, were used to model herbicide concentrations entering the Rangitaiki River for the remaining treated areas in the catchment for the same two spray seasons. A spreadsheet model routed herbicide residues from their point of entry into the river to a flow gauge on the Rangitaiki River. Modeling of chemical residue loadings and concentrations of terbuthylazine and hexazinone indicated that potential herbicide residues in stream waters would be mainly below analytical detection limits and pose no risk to the aquatic environment or human health and safety. Safety factors for drinking water quality standards, aquatic organisms, and human Acceptable Daily Intake levels were very large.
Highlights
Modeling of chemical residue loadings and concentrations of terbuthylazine and hexazinone indicated that potential herbicide residues in stream waters would be mainly below analytical detection limits and pose no risk to the aquatic environment or human health and safety
The herbicide application sites were reasonably well distributed throughout the planted forest portion of the upper Rangitaiki River catchment (Figure 2)
In landscapes that have intense and extensive forest management, the big question becomes “Are there water quality effects that occur from multiple uses of herbicides within the same landscape and over time?” This is where a cumulative effects analysis becomes very important for both forest managers, regulators and the general public
Summary
Water quality is a relative concept that is based on measurable physical, chemical, and biological characteristics in relation to specific uses such as human consumption, crop irrigation, livestock watering, fisheries maintenance, recreation, and aquatic habitat [1]. Water quality integrates the current state of ecosystem health as well as the effects of disturbance within the aquatic ecosystem. Forested watersheds produce sustainable supplies of high quality water based on two fundamental reasons [6]. Forests grow under climate conditions that usually produce consistent amounts of high quality streamflow. The precipitation needed to promote and sustain forest growth is adequate to sustain stream baseflows, which is important for maintaining aquatic habitat [3,4,5,6].
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
