# Basin General watershed attributes are defined in two basin input files, [**codes.bsn**](/io-docs/introduction-1/basin-1/codes.bsn.md) and [**parameters.bsn**](/io-docs/introduction-1/basin-1/parameters.bsn.md). These attributes control a diversity of physical processes at the watershed level. Users can use the default values set by the interfaces or change them to better reflect what is happening in a given watershed. {% hint style="info" %} Even if nutrients are not being studied in a watershed, some attention must be paid to basin nutrient variables, because nutrient cycling impacts plant growth, which in turn affects the hydrologic cycle. \ Variables governing bacteria or pesticide transport need to be initialized only if these processes are being modeled in the watershed. {% endhint %} --- # 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/basin-1.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.