Modeling phosphorus concentrations in Irish rivers using land use, soil type, and soil phosphorus data

• Published in: Journal of environmental quality 2002-03, Vol.31 (2), p.590-599
• Main Authors: DALY, Karen, MILLS, Paul, COULTER, Brian, MCGARRIGLE, Martin
• Format: Article
• Language: English
• Subjects: Agriculture; Applied sciences; Continental surface waters; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Environment; Environmental monitoring; Exact sciences and technology; Fertilizers; Field tests; Forecasting; Grasslands; Hydrologic data; Hydrology; Ireland; Land management; Land use; Models, Theoretical; Natural water pollution; Overland flow; Phosphorus; Phosphorus - analysis; Poaceae; Pollution; Pollution, environment geology; River catchments; Rivers; Sensitivity and Specificity; Soil hydrology; Soil Pollutants - analysis; Soil surveys; Soil testing; Soil types; Stream discharge; Stream flow; Surface water; Water Movements; Water Pollutants - analysis; Water treatment and pollution
• ISSN: 0047-2425; 1537-2537; 1537-2537
• DOI: 10.2134/jeq2002.0590

Modeling diffuse phosphorus (P) loss may indicate management strategies to minimize P loss from agricultural sources. An empirical model predicting flow-weighted phosphorus concentrations (MRP) was derived using data collected from 35 Irish river catchments. Monitoring records of riverine P and stream flow data were used to calculate MRP values averaged for the years 1991-1994. These data were modeled using land use, soil type, and soil P data. Soil type in catchments was described using soil survey classifications weighted according to their P desorption properties from laboratory results. Soil test P concentrations for the studied watersheds were obtained from a national database. Soil P levels were weighted based on the results of field experiments measuring P losses in overland flow from fields at different soil test P levels. The 35 catchments were statistically clustered into two populations (A and B) based on differences in soil type, specifically, soil hydrology. Catchments in Cluster A had predominantly poorly drained soils and comparatively higher MRP concentrations (0.03-0.17 mg L(-1)) than Cluster B areas (0.01-0.7 mg L(-1)) with mostly well-drained soils. Regression equations derived for A and B type catchments predicted MRP values with 68 and 62% of the variation explained in the models, respectively. Data extracted for the rest of the country were applied to the models to delineate areas at risk on a national scale. While the models were only moderately accurate they highlighted the influence of land management, specifically, high production grassland receiving high P inputs, in conjunction with the effect of soil type and soil hydrology on the transport of P to surface waters.