---
title: "Rating Curve | Technical Reference"
slug: "rating-curve"
description: "Find the theory and guidance for the rating curve unit. "
tags: ["1D river modelling", "rating curve"]
updated: 2022-09-21T18:22:39Z
published: 2022-09-21T18:22:39Z
canonical: "help.floodmodeller.com/rating-curve"
stale: true
---

> ## Documentation Index
> Fetch the complete documentation index at: https://help.floodmodeller.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Rating Curve

This unit specifies a rating curve at a given node. Its primary purpose is to allow water levels to be generated at Muskingum routing nodes.

## Theory and Guidance

### General

This unit specifies a rating curve at a given node. Its primary purpose is to allow water levels to be generated at Muskingum routing nodes.

This unit only gives information when required: it does not have any computation phase and can be placed anywhere in the data file. Basically, this unit is used when the flow is split at a rating junction, or when solving mixed reaches (those formed by combining hydrodynamic reaches solved by the full Saint Venant equations) and flood routing reaches.

### Usage

To add a rating curve unit into your network, right-click on the network table and select 'insert' > 'rating curve', as shown below.

![RiverNodesimagesratingimage185.png](https://cdn.document360.io/5074bc26-a9ef-4bf4-b1de-a5c6ce628aca/Images/Documentation/RiverNodesimagesratingimage185.png)

Only one node is attached to this unit.

## Data

| Field in Data Entry Form | Description | Name in Datafile |
| --- | --- | --- |
| Node Label | label of node at which rating curve is defined | Label |
| n/a | number of q, h data pairs | ndat |
| Flow | flow associated with water level hi (m3/s) | qi |
| Water Level | water level at flow qi (mAD) | hi |

## Datafile Format

### General

Line 1 : keyword 'QRATING' [comment]

Line 2 : Label

Line 3 : ndat

Line 4 to Line 3+ndat : qi, hi

where ndat is the number of data sets following, items in square brackets are optional, and other parameters are as defined in the [data section](/v1/docs/rating-curve#data).

### Example

```none
QRATING
UNIT056
         4
     0.000     0.000
     1.000     0.100
     2.000     0.200
     3.000     0.300
```