Uncertainty in nutrient loads from tile-drained landscapes: Effect of sampling frequency, calculation algorithm, and compositing strategy

摘要: Summary Accurate estimates of annual nutrient loads are required to evaluate trends in water quality following changes land use or management and calibrate validate models. While much emphasis has been placed on understanding the uncertainty load large, naturally drained watersheds, few studies have focused tile-drained fields small headwater watersheds. The objective this study was quantify dissolved reactive phosphorus (DRP) nitrate-nitrogen (NO 3 -N) from four two watersheds Ohio, USA Ontario, Canada. High temporal resolution datasets discharge (10–30 min) concentration (2 h 1 d) were collected over a 1–2 year period at each site used calculate reference load. Monte Carlo simulations subsample measured data assess effects sample frequency, calculation algorithm, compositing strategy estimates. Results showed that DRP NO -N influenced by both sampling interval estimation algorithm. Uncertainty increased with increasing for all algorithms tested. Continuous measurements linear interpolation concentrations yielded least amount uncertainty, but still tended underestimate Compositing strategies generally improved precision compared discrete grab samples; however, they often reduced accuracy. Based results study, we recommended be every 13–26 h 2.7–17.5 d accurately (±10%) estimate loads.