Converting Depth to Discharge

Converting Depth to Discharge

Hydrologists routinely use measurements of Depth and Discharge to produce what is known as a Rating Table or Curve. The Rating Table is a mathematically modelled relationship between the water surface elevation and the quantity of water moving through that location. These rating tables are typically derived from both hydraulic theory and actual field measurements of discharge taken at various water elevations, and they can be applied to the time series of water level record to determine a time series of discharge.

Before undertake this conversion, you need to have an applicable rating table, i.e. a DataSight Conversion Table, in the DataSight Conversion Table module.

 

Create a theoretical Rating Table in DataSight

(See also Create a Conversion Table for more details).

  1. Open Conversion Tables.
  2. Enter Depth and Discharge as the X and Y labels, respectively. This can be undertaken manually or by pasting directly from an electronic file to populate the conversion table.
  3. Enter dates for the Period of Applicability.
  4. Save the conversion table.

 

Use a Rating Table to Convert Depth to Discharge

  1. Ensure the Variables Depth and Discharge are displayed in your datasheet.
  2. Right-click on the datasheet and select Calculation.
  3. In the Calculation window select the appropriate Level for Master Variable A.
  4. SelectDepth as Master Variable A.
  5. Check Use Conversion Table.
  6. Select the Saved Conversion Table from the drop-down list.
  7. Select the Conversion Method.
  8. When completing conversions using a Conversion Table, the Formula entered can simply be A (or lowercase, a).
  9. Select the Output Variable Discharge at desired level.
  10. Select the Calculation Chart tab, where you can review the calculation input variables and the result of the proposed calculation.
  11. Similarly, select the Calculation Result tab to review the data in grid view, before completing the calculation.
  12. Check the Database button and click Update.
  13. Close the Calculation Tool and open/refresh your datasheet. The Discharge variable has been populated within the datasheet.

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