# cha\_ob | Option | Description | | ------ | ------------------ | | yes | One channel object | | no | No channel object | There cannot be more than one channel object per water allocation table. If one of the source objects is a channel, the water allocation module is called from the channel control subroutine when the simulation reaches the ID of the source channel. Otherwise, the water allocation module is called from the time control subroutine. This is important, because during a model run, there is more variability in the availability of water in a channel than in a reservoir or aquifer. Therefore, the model needs to know the current availability of water in the source channel on the day a demand is triggered. --- # 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/introduction-1/water-allocation/water_allocation.wro/cha_ob.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.