Guiding riparian management in a transboundary watershed through high resolution spatial statistical network models

Area of Science:

• Environmental Science
• Hydrology
• Spatial Statistics

Background:

• Stream temperature is a critical factor for aquatic ecosystems, influencing fish survival and habitat suitability.
• Transboundary watersheds present unique challenges for environmental monitoring and data management due to political boundaries.
• Riparian buffers are essential for regulating stream temperature and maintaining aquatic ecosystem health.

Purpose of the Study:

• To develop a high-resolution spatial statistical network (SSN) model for predicting stream temperatures in the Meduxnekeag Watershed.
• To assess the impact of different riparian buffer restoration scenarios on stream temperatures and cold water habitat.
• To provide data-driven guidance for riparian restoration projects aimed at enhancing cold water fish habitat.

Main Methods:

• Development of a spatial statistical network (SSN) model using the High-Resolution National Hydrology Dataset Plus for fine-resolution (1:24,000) temperature predictions.
• Modeling of median stream temperatures for July, August, and September, and growing season maximum (GSM) temperatures.
• Prediction of stream temperatures under dry (2010) and wet (2011) year conditions and evaluation of restoration scenarios with 30-m and 90-m riparian buffers.

Main Results:

• Fitted SSN models demonstrated high accuracy (R²: 0.88-0.96) with significant parameters including solar radiation, reference flow, air temperature, and bankfull dimensions.
• Monthly models indicated fewer cold water reaches in July (28% dry year, 68% wet year) and over 99% cold water reaches in September.
• Growing season maximum predictions showed 81% of reaches unsuitable for salmonids in the dry year and 59% as warmwater habitat in the wet year.

Conclusions:

• Riparian restoration scenarios, specifically 30-m and 90-m buffers, effectively expanded cold water habitat and reduced areas exceeding salmonid survival thresholds.
• Both buffer widths showed similar effectiveness in improving stream temperatures for cold water species.
• The developed SSN model serves as a valuable tool for guiding the Houlton Band of Maliseet Indians' riparian restoration efforts to benefit cold water fishes.