Process Based Modelling of Phosphorus Losses from Arable Land

Abstract

Improved understanding of temporal and spatial Phosphorus (P) discharge variations is needed for improved modelling and prioritisation of abatement strategies that take into account local conditions . This study is aimed at developing modelling of agricultural Phosphorus losses with improved spatial and temporal resolution, and to compare the accuracy of a detailed process-based model with a rainfall-runoff coefficient-based model. The process-based SWAT model (Soil and Water Assessment Tool) was implemented for five river basins in central Sweden, and results compared with the rainfall-runoff coefficient-based model WATSHMAN (Watershed Management System) for one of these river basins. Parameter settings and attribute values were adapted to Scandinavian soil conditions, crops and management practices. Model performance regarding flow dynamics was overall satisfactory. Comparable results were achieved at several scales. The modelled P load was of high accuracy for the days when monitoring data were available for validation, generally once a month. Modelled monthly P load did not fit as well with averaged monthly monitoring load values, mainly since monthly monitoring often partly or entirely misses the peak flows. The comparison of SWAT and WATSHMAN gave slightly better results for the processbased model (SWAT). Better spatial resolution for input data such as Soil-P content and agricultural management practices will be required to reach modelling results that enable identification of measures adapted to local conditions.

Spatial Quantification of Non-Point Source Pollution in a Meso-Scale Catchment for an Assessment of Buffer Zones Efficiency

“…In summary, our results support the findings of Ekstrand et al [58], who applied SWAT to model the TP losses in five catchments in central Sweden. Overall, Ekstrand et al [58] observed that obtaining satisfactory results for a validation period often depends on whether the range of hydroclimatological conditions is similar (as in calibration).…”

“…However, the reported values of PBIAS for most of the gauges are within the ranges of satisfactory performance for discharge (+/-25%) and the NO 3 -N and TP loads (+/-70%) [49]. In summary, our results support the findings of Ekstrand et al [58], who applied SWAT to model the TP losses in five catchments in central Sweden. Overall, Ekstrand et al [58] observed that obtaining satisfactory results for a validation period often depends on whether the range of hydroclimatological conditions is similar (as in calibration).…”

A review of phosphorus and sediment release from Irish tillage soils, the methods used to quantify losses and the current state of mitigation practice

“…In the short term, Nasr et al (2005) recommended using SWAT for TP load estimation. The SWAT model recently showed good potential for predicting TP losses from arable land in a Swedish study by Ekstrand et al (2010) (Table 4). TOPMODEL is a process based semidistributed catchment model (Irvine et al 2005) in which the major factors affecting runoff generation are the catchment topography and the soil transmissivity, which diminishes with depth (Parsons et al 2001).…”

Particulate phosphorus accumulation and net retention in constructed wetlands receiving agricultural runoff : Critical analysis of factors affecting retention estimates

“…Similarly, Pionke et al (2000) showed that 90% of the P export from an agricultural watershed in the USA occurred during storm flow, which represented 10% of the time. Ekstrand et al (2010) observed that in a >800 km 2 large catchment, 76% of the annual stream TP transport was discharged during 18 days in December and January. Such sudden events will have a significant impact on P transport from arable lands.…”