One of my student is doing her research work on eutrophication model of a lake ecosystem; since most of the modelling software are made for the system with tributaries; can anyone help me in find out the modelling tool for the assessment of eutrophication level without having any tributaries.
Could you not use a tributary model and set the tributary values at 0?
Please check this paper: Barbieri A, Simona M. Trophic evolution of Lake Lugano related to external load reduction: Changes in phosphorus and nitrogen as well as oxygen balance and biological parameters. Lakes and Reservoirs Research and Management. 2001;6(1):37–47. doi: 10.1046/j.1440-1770.2001.00120.x
As Ian said, you can assume that the nutrient and organic matter supply by point tributaries being equal to 0. However I suggest that you carefully consider all the rest of possible sources, which include, for instance, diffused runoff, atmospheric deposition, external animals dropping, internal load, etc