The Phosphorus Indicators Tool: a simple model of diffuse P loss from agricultural land to water

Abstract

Abstract. The Phosphorus Indicators Tool provides a catchment‐scale estimation of diffuse phosphorus (P) loss from agricultural land to surface waters using the most appropriate indicators of P loss. The Tool provides a framework that may be applied across the UK to estimate P loss, which is sensitive not only to land use and management but also to environmental factors such as climate, soil type and topography. The model complexity incorporated in the P Indicators Tool has been adapted to the level of detail in the available data and the need to reflect the impact of changes in agriculture. Currently, the Tool runs on an annual timestep and at a 1 km2 grid scale. We demonstrate that the P Indicators Tool works in principle and that its modular structure provides a means of accounting for P loss from one layer to the next, and ultimately to receiving waters. Trial runs of the Tool suggest that modelled P delivery to water approximates measured water quality records. The transparency of the structure of the P Indicators Tool means that identification of poorly performing coefficients is possible, and further refinements of the Tool can be made to ensure it is better calibrated and subsequently validated against empirical data, as it becomes available.

The phosphorus transfer continuum: Linking source to impact with an interdisciplinary and multi-scaled approach

“…This is similar to classical dsource-pathway-receptorT models that are well proven. Its evolution can be traced back to indexing approaches (Lemunyon and Gilbert, 1993), the arrangement of a European Research Programme (Withers, 1997), conceptual models Jarvis, 1998, 1999), the structure for an international conference , and approaches which also formed the focus of modelling frameworks (Heathwaite et al, 2003). This four tiered framework is called the dP transfer continuumT to emphasise the interdisciplinary and interconnected nature of the science (Fig.…”

“…timing of manure and fertilizer applications) and over longer timescales (e.g. in response to economic drivers such as reform of European Union Common Agricultural Policy) (Heathwaite et al, 2003). Withers and Jarvis (1998) Source Refers to the raw inputs of phosphorus to the agricultural system, such as fertilizer, feed, mineralised from soil or atmospheric deposition.…”

“…Sediment tracking and fingerprinting techniques to demonstrate a direct physical link (Walling and He, 1999 (Heathwaite et al, 2003;Whitehead et al, in press). …”

Spatial Model Assessment of P Transport from Soils to Waterways in an Eastern Mediterranean Watershed

“…To achieve this, a spatial model that will run over several hydrological years is required to aid in establishing better watershed-management practices. Several models and indices have been developed for agro-watersheds in temperate climates in Europe, North America and Australia (e.g., [7,[15][16][17][18]), but little work has been done in agro-watersheds in Mediterranean climates which are characterized by a few rainfall-runoff events.…”

Prediction of storm transfers and annual loads with data-based mechanistic models using high-frequency data

“…In most models there is a balance between practical simplifications and model complexity, which depends on catchment size and knowledge (or lack thereof) of the hydrological processes, data availability and computing power. Some of the less complex models for diffuse pollution include export coefficient models (Johnes, 1996) and the phosphorus indicators tool (PIT) (Heathwaite et al, 2003;Liu et al, 2005). The most complex water quality models are idealised, process-based representations of our best understanding of reality, with a highly complex, fixed structure and many parameters, for which there is often little or no site-specific data (Dean et al, 2009).…”