Articles | Volume 15, issue 7
Biogeosciences, 15, 2251–2269, 2018
Biogeosciences, 15, 2251–2269, 2018

Research article 17 Apr 2018

Research article | 17 Apr 2018

QUAL-NET, a high temporal-resolution eutrophication model for large hydrographic networks

Camille Minaudo1,2, Florence Curie1, Yann Jullian3, Nathalie Gassama1, and Florentina Moatar1 Camille Minaudo et al.
  • 1E.A. 6293 GeHCO, François Rabelais Tours University, Tours, 37000, France
  • 2OSUR-CNRS, Rennes 1 University, Rennes, 35000, France
  • 3CaSciModOT, UFR Sciences et Techniques, François Rabelais Tours University, Tours, 37000, France

Abstract. To allow climate change impact assessment of water quality in river systems, the scientific community lacks efficient deterministic models able to simulate hydrological and biogeochemical processes in drainage networks at the regional scale, with high temporal resolution and water temperature explicitly determined. The model QUALity-NETwork (QUAL-NET) was developed and tested on the Middle Loire River Corridor, a sub-catchment of the Loire River in France, prone to eutrophication. Hourly variations computed efficiently by the model helped disentangle the complex interactions existing between hydrological and biological processes across different timescales. Phosphorus (P) availability was the most constraining factor for phytoplankton development in the Loire River, but simulating bacterial dynamics in QUAL-NET surprisingly evidenced large amounts of organic matter recycled within the water column through the microbial loop, which delivered significant fluxes of available P and enhanced phytoplankton growth. This explained why severe blooms still occur in the Loire River despite large P input reductions since 1990. QUAL-NET could be used to study past evolutions or predict future trajectories under climate change and land use scenarios.

Short summary
We developed the model QUALity-NETwork (QUAL-NET) to simulate water quality variations in large drainage networks. This model is accurate enough to represent processes occurring over short periods of time such as storm events and helps to fully understand water quality variations in stream networks in the context of climate change and varying human pressures. It was tested on the Loire River and provided good performances and a new understanding of the functioning of the river.
Final-revised paper