『Abstract
Watershed losses of phosphorus (P) have been a topic of concern
for water resource managers over recent decades. To evaluate environmental
policies or before implementing mitigation options at the watershed
(catchment area) scale, stakeholders often need to analyze the
patterns of point and diffuse sources of phosphorus. This information
is often not easy to obtain in field conditions. Several statistical
modeling approaches have been developed in recent years to respond
to this basic operational demand. Point and diffuse sources are
often evaluated from power functions established between phosphorus
concentration and water discharge. Such models do not explicitly
account for in-stream processes which control P concentrations
in the hydrographic network and differentiate the P export dynamics
of the various forms and inputs of P. To identify the phosphorus
sources and evaluate their change in response to environmental
policies, we developed a simple and loaded-oriented model (POPEYE
- PhOsPhorus, Evaluation of the efficiencY of Environmental policy
measures) that computes retention, settling and re-suspension
rates of fine and coarse P fractions and their relation to P concentration
of bed sediments. The model is calibrated to a long-term database
(25 years), and describes the weekly water and chemical fluxes
of a tributary of Lac Leman（eの頭に´） (Lake
Geneva, Venoge river watershed, 240 km2). It adequately
predicts observed values of fine and particulate phosphorus and
reflects the gradual decrease of point and diffuse inputs over
the studied period due to agricultural and sewage treatment policies
implemented for the control of lake pollution.
Keywords: Phosphorus; Eutrophication; Point sources; Diffuse sources;
Sediment; Pollution』
1. Introduction
2. Methodology
2.1. Study site
2.2. Water data base
2.3. Model development
2.3.1. Total phosphorus PT
2.3.2. Soluble phosphorus PS
2.4. Parameterization
2.5. Model validation
3. Results and commentary
3.1. Overview of water quality and trends over the last 30
years
3.2. Modeling
3.2.1. Model adequacy
3.2.2. Point losses
3.2.3. Water/sediment exchanges
3.2.4. Diffuse losses
4. Discussion
4.1. Relevance and limitations of the model
4.2. Outdraws
4.3. Conditions for the use of POPEYE
5. Conclusion
Acknowledgments
References