If you'd like to learn more about i-Tree's hydrology engine, with specific interest in how it differs from Curve Number and handles subsurface moisture tracking, here are some efficient options to explore:
- Slides 14-20 of http://www.itreetools.org/resources/pre ... rology.pdf offer a solid overview. A little more detail you may find helpful continues through slides 21-31.
- i-Tree Hydro models subsurface moisture using Topographic Index (TI) theory from TOPMODEL. Our above-ground processes are explicit and sub-surface processes are an improvement from CN, but we do simplify things a bit below ground. If you want to learn more about our use of TI theory, I recommend our Wang et al. 2008 model methods paper (http://www.itreetools.org/hydro/resourc ... dology.pdf), specifically: section titled "Infiltration Into Soils", and 2nd-to-last paragraph of section titled "Overland, Impervious, and Subsurface Runoff" (in other words, first paragraph on page 81).