Environmental modelling is a broad subject. At the undergraduate level, I believe one should give a broad panoramic of the field and make emphasis in teaching the methodology and the process. A couple of really good books that I have used in my courses that satisfy these requirements are:
Acevedo M. 2002. Simulation of Ecological and Environmental Models (https://www.crcpress.com/Simulation-of-Ecological-and-Environmental-Models/Acevedo/p/book/9781439885062)
Haefner, J. 2005. Modeling Biological Systems: Principles and Applications. (https://www.springer.com/gp/book/9780387250113).