A qualitative model of the nutrient spiraling in lotic ecosystems to support decision makers for river management

The spiraling of resources in stream ecosystems is a well known phenomenon in the scientific literature. We implemented the necessary components of a nutrient cycle in a qualitative reasoning approach. The model includes entities that represent segments of a river and quantities for nutrients, autotrophs, and detritus, and employs three rates: uptake rate (from nutrients to autotrophs), retention rate (from autotrophs to detritus), and release rate (from detritus to nutrients) within the nutrient cycle. Each river segment also has a flow rate allowing only the nutrients to move from one segment to another. To enable the users to specify the character of a river segment we used attributes and to represent influences from the catchment area we used agents. The ideas presented in this paper represent our first approach to create an easy-to-use simulation setup so that stakeholders and decision makers can simulate specific scenarios and develop causal models of specific stream phenomena.