Introduction to the Model Merger Exercise

Chapter 4 describes a model to simulate changes in the size of Mono Lake based on different policies governing the amount of water exported to Los Angeles. The model helps us understand the long term changes in the size of the lake, but it provides little understanding of whether the food web is in danger. Chapter 4 relies on the "proxy" approach. It simulates changes in the lake's elevation, and we interpret low values of the elevation as an indicator of an endangered ecosystem. In this exercise, we want move beyond the "proxy" approach. Our goal is to make our assumptions about the ecosystem more explicit. Mono Lake is home to an interesting food web comprised of planktonic and benthic algae, brine shrimp, brine flies and a variety of migrating and nesting birds. (Click here to see a large drawing of the food web.). This exercise focuses on the brine shrimp, a key participant in the ecosystem.

The Brine Shrimp (photo courtesy of the Mono Lake Committee)

This exercise begins with a model of the brine shrimp population. You are to imagine that the population model has been developed independently of the hydrology model in Chapter 4. Your job is to merge the two models to provide an internally consistent simulation of size of the brine shrimp population as well as the size of the lake.

You will discover what many modeling teams discover when working in large organizations --independently developed models do not necessarily fit together just because they deal with the same topic. You will need to make some adjustments in one or both of the models in order to combine them into a holistic picture of Mono Lake. If you succeed, you may use the combined model to simulate a new policy governing the amount of water exported from the basin.