A case study of river temperature response to agricultural land use and environmental thermal patterns

ABSTRACT:

Water temperature standards are being implemented in various states. This may impact agricultural land management. We evaluated the association between river temperature patterns, existing agricultural land uses, and the thermal equilibrium condition of the surrounding environment (e.g. air and soil temperatures). This case study was conducted on irrigated hay (meadow and wet meadow ecological sites) and pasture (sodic meadow ecological site) land in northeastern Oregon. Shading over the river channel (approximately 12 m channel width) was estimated at 1 to 5% based on site characteristics. Daily mean and maximum stream temperature increases along approximately 1.6 km (1.0 ml) reach lengths were 0 to 0.1 and 0.1 to 0.2°C, respectively, and were not different between existing land uses/ecological sites. Mean air and water temperatures were approximately 1°C apart indicating that an equilibrium condition existed during the study. As expected when temperatures approach equilibrium, weather conditions were the dominant influence on river temperature, much more than land use influences.