> For the complete documentation index, see [llms.txt](https://swatplus.gitbook.io/io-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://swatplus.gitbook.io/io-docs/theoretical-documentation/section-7-main-channel-processes/in-stream-nutrient-processes/algae/algal-growth.md).

# Algal Growth

Growth and decay of algae/chlorophyll $$a$$ is calculated as a function of the growth rate, the respiration rate, the settling rate and the amount of algae present in the stream. The change in algal biomass for a given day is:

$$\Delta algae=((\mu \_a*algae)-(\rho\_a*algae)-(\frac{\sigma\_1}{depth}\*algae))\*TT$$                             7:3.1.2

where $$\Delta algae$$ is the change in algal biomass concentration (mg alg/L), $$\mu\_a$$ is the local specific growth rate of algae (day$$^{-1}$$ or hr$$^{-1}$$), $$\rho\_a$$ is the local respiration or death rate of algae (day$$^{-1}$$ or hr$$^{-1}$$), $$\sigma\_1$$ is the local settling rate for algae (m/day or m/hr), $$depth$$ is the depth of water in the channel (m), $$algae$$ is the algal biomass concentration at the beginning of the day (mg alg/L), and $$TT$$ is the flow travel time in the reach segment (day or hr). The calculation of depth and travel time are reviewed in Chapter 7:1.


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## 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, and the optional `goal` query parameter:

```
GET https://swatplus.gitbook.io/io-docs/theoretical-documentation/section-7-main-channel-processes/in-stream-nutrient-processes/algae/algal-growth.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

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.