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Modeling Phosphorus in the Lake Allatoona Watershed Using SWAT: I. Developing Phosphorus Parameter Values
Author(s) -
Radcliffe D. E.,
Lin Z.,
Risse L. M.,
Romeis J. J.,
Jackson C. R.
Publication year - 2009
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2007.0110
Subject(s) - phosphorus , watershed , environmental science , swat model , hydrology (agriculture) , chemistry , geology , computer science , geotechnical engineering , organic chemistry , machine learning
Lake Allatoona is a large reservoir north of Atlanta, GA, that drains an area of about 2870 km 2 scheduled for a phosphorus (P) total maximum daily load (TMDL). The Soil and Water Assessment Tool (SWAT) model has been widely used for watershed‐scale modeling of P, but there is little guidance on how to estimate P‐related parameters, especially those related to in‐stream P processes. In this paper, methods are demonstrated to individually estimate SWAT soil‐related P parameters and to collectively estimate P parameters related to stream processes. Stream related parameters were obtained using the nutrient uptake length concept. In a manner similar to experiments conducted by stream ecologists, a small point source is simulated in a headwater sub‐basin of the SWAT models, then the in‐stream parameter values are adjusted collectively to get an uptake length of P similar to the values measured in the streams in the region. After adjusting the in‐stream parameters, the P uptake length estimated in the simulations ranged from 53 to 149 km compared to uptake lengths measured by ecologists in the region of 11 to 85 km. Once the a priori P‐related parameter set was developed, the SWAT models of main tributaries to Lake Allatoona were calibrated for daily transport. Models using SWAT P parameters derived from the methods in this paper outperformed models using default parameter values when predicting total P (TP) concentrations in streams during storm events and TP annual loads to Lake Allatoona.