# 2:2.3.2 Transpiration If the Penman-Monteith equation is selected as the potential evapotranspiration method, transpiration is also calculated with the equations summarized in Section 2:2.2.1. For the other potential evapotranspiration methods, transpiration is calculated as: $$E\_t=\frac{E'\_o\*LAI}{3.0}$$ when $$0 \le LAI \le 3.0$$ 2:2.3.5 $$E\_t=E'\_o$$ when $$LAI>3.0$$ 2:2.3.6 where $$E\_t$$ is the maximum transpiration on a given day (mm H$$\_2$$O), $$E'\_o$$ is the potential evapotranspiration adjusted for evaporation of free water in the canopy (mm H$$\_2$$O), and $$LAI$$ is the leaf area index. The value for transpiration calculated by equations 2:2.3.5 and 2:2.3.6 is the amount of transpiration that will occur on a given day when the plant is growing under ideal conditions. The actual amount of transpiration may be less than this due to lack of available water in the soil profile. Calculation of actual plant water uptake and transpiration is reviewed in Chapters 5:2 and 5:3. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://swatplus.gitbook.io/io-docs/theoretical-documentation/section-2-hydrology/chapter-2-2-evapotranspiration/2-2.3-actual-evapotranspiration/2-2.3.2-transpiration.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.