Comparison of measured and simulated phosphorus losses with indexed site vulnerability

T. L. Veith, A. N. Sharpley, J. L. Weld, W. J. Gburek

Research output: Contribution to journalArticle

54 Citations (Scopus)

Abstract

Nonpoint-source losses of agricultural phosphorus (P) at field and watershed scales must be quantified to facilitate selection and placement of P control measures. Quantification of P loss has been pursued through field monitoring, simulation models, and risk assessment indices. However, the intended users of these methods differ, impacting each method's functional design and ease-of-use. For example, the Pennsylvania P Index, a risk assessment tool for planners, requires less discipline-specific knowledge and more readily available data than the Soil and Water Assessment Tool (SWAT), a complex, watershed-level, research-based simulation model. This study compared measured losses of P from the outlet of a 39.5 ha mixed land use watershed (FD-36) in south-central Pennsylvania with watershed-level losses predicted by SWAT. Measured watershed exports of dissolved P (0.06 kg ha-1) and total P (0.24 kg ha-1) during the 7-month sampling period were similar in magnitude to SWAT-predicted losses (0.05 and 0.73 kg ha-1, respectively). Additionally, the study compared field-level P losses predicted by SWAT with field-level vulnerabilities to P loss derived by the P Index. The P Index and SWAT categorized 73% of the 22 fields similarly in terms of vulnerability to P loss, with Pearson correlation significant at p = 0.07; all except one of the remaining six fields were over- or underpredicted by a single risk category. Results indicate that while actual P loss from FD-36 was small, three fields contributed a major proportion of this loss. Additionally, this study suggests that the P Index can provide land managers with a reliable assessment of where P loss occurs within a watershed, thus allowing more effective placement and selection of conservation practices, which lead toward improved downstream water quality.

Original languageEnglish (US)
Pages (from-to)557-565
Number of pages9
JournalTransactions of the American Society of Agricultural Engineers
Volume48
Issue number2
StatePublished - Mar 1 2005

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Soil and Water Assessment Tool model
Phosphorus
vulnerability
Soil
phosphorus
Water
Watersheds
watershed
risk assessment
Soils
simulation models
Water Quality
conservation practices
Risk assessment
comparison
loss
control methods
managers
water quality
land use

All Science Journal Classification (ASJC) codes

  • Agricultural and Biological Sciences (miscellaneous)

Cite this

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title = "Comparison of measured and simulated phosphorus losses with indexed site vulnerability",
abstract = "Nonpoint-source losses of agricultural phosphorus (P) at field and watershed scales must be quantified to facilitate selection and placement of P control measures. Quantification of P loss has been pursued through field monitoring, simulation models, and risk assessment indices. However, the intended users of these methods differ, impacting each method's functional design and ease-of-use. For example, the Pennsylvania P Index, a risk assessment tool for planners, requires less discipline-specific knowledge and more readily available data than the Soil and Water Assessment Tool (SWAT), a complex, watershed-level, research-based simulation model. This study compared measured losses of P from the outlet of a 39.5 ha mixed land use watershed (FD-36) in south-central Pennsylvania with watershed-level losses predicted by SWAT. Measured watershed exports of dissolved P (0.06 kg ha-1) and total P (0.24 kg ha-1) during the 7-month sampling period were similar in magnitude to SWAT-predicted losses (0.05 and 0.73 kg ha-1, respectively). Additionally, the study compared field-level P losses predicted by SWAT with field-level vulnerabilities to P loss derived by the P Index. The P Index and SWAT categorized 73{\%} of the 22 fields similarly in terms of vulnerability to P loss, with Pearson correlation significant at p = 0.07; all except one of the remaining six fields were over- or underpredicted by a single risk category. Results indicate that while actual P loss from FD-36 was small, three fields contributed a major proportion of this loss. Additionally, this study suggests that the P Index can provide land managers with a reliable assessment of where P loss occurs within a watershed, thus allowing more effective placement and selection of conservation practices, which lead toward improved downstream water quality.",
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Comparison of measured and simulated phosphorus losses with indexed site vulnerability. / Veith, T. L.; Sharpley, A. N.; Weld, J. L.; Gburek, W. J.

In: Transactions of the American Society of Agricultural Engineers, Vol. 48, No. 2, 01.03.2005, p. 557-565.

Research output: Contribution to journalArticle

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