Dynamic phosphorus mass balance modeling of large watersheds: long-term implications of management strategies.
The principles of mass balance, compartment-flux diagramming, and dynamic simulation modeling are integrated to create computer models that estimate phosphorus (P) export from large-scale watersheds over long-term futures. These Watershed Ecosystem Nutrient Dynamics (WEND) models are applied to a 275,000 ha dairy-documented watershed and a 77,000 ha poultry-dominated watershed in northeastern USA. Model predictions of present-day P export loads are consistent with monitoring data and estimates made using P export coefficients. For both watersheds P import exceeds P export and P is accumulating in the agricultural soils. Agricultural and urban activities are major contributors to P export from both watersheds. Continued urban growth will increase P export over time unless wastewater management is substantially enhanced and/or rates of urban growth are controlled. Agriculture cannot rely solely on the implementation of increasingly stringent conservation practices to reduce long-term P export but must consider options that promote P input/output balance. The WEND modeling process is a powerful tool to integrate the diversity of activities in watersheds into a holistic framework. Model outputs are suited to assist managers to explore long-term effects of overall watershed management strategies on P export in comparison to environmental and economic goals.
Cassell
E A
EA
School of Natural Resources, University of Vermont, Burlington, VT 05405, USA.
Kort
R L
RL
Meals
D W
DW
Aschmann
S G
SG
Dorioz
J M
JM
Anderson
D P
DP
D000383:Agriculture; D002947:Cities; D003198:Computer Simulation; D017753:Ecosystem; D005068:Eutrophication; D006801:Humans; D008962:Models, Theoretical; D010758:Phosphorus / Q000737:chemistry*; D012037:Refuse Disposal; D014872:Water Movements; D014876:Water Pollution / Q000191:economics / Q000517:prevention & control*
D010758:Phosphorus