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CD-Rainfall method

CD-Rainfall method. A quick method to make a groundwater balance. CD-Rainfall method. The Cumulative Departure-Rainfall (CD-Rainfall) method is a method to rapidly understand groundwater conditions. It only requires: Periodic rainfall data Ground water level data. CD-Rainfall method.

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CD-Rainfall method

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  1. CD-Rainfall method A quick method to make a groundwater balance

  2. CD-Rainfall method The Cumulative Departure-Rainfall (CD-Rainfall) method is a method to rapidly understand groundwater conditions. It only requires: • Periodic rainfall data • Ground water level data

  3. CD-Rainfall method • Above average rainfall results in an increase of water tables. • Below average rainfall results in a decline It uses the assumption that in normal conditions groundwater levels quickly react to rainfall:

  4. Recharge - Rainfall • Water level – Mean rainfall • Water level – Above mean rainfall • Water level – Below mean rainfall

  5. In the CD rainfall you calculate: • Departure (difference) from normal rainfall for the period • Then calculate the cumulative departure (=CD) • And compare this with groundwater levels • Take a close look at the next table >>

  6. Difference with monthly average Cumulative departure

  7. Comparing the ‘cumulative rainfall departure’ with groundwater levels allows us to understand recharge and overuse

  8. ‘No overuse’: Water level follows CD-rainfall Rainfall – water level relation ‘No over-use’: Water level follows CD-rainfall

  9. Another ‘normal’ situation

  10. Overuse: water level drops even though CD rainfall goes up

  11. Recharge and discharge to a river: The relation between CD-rainfall and water levels is not clear

  12. Presentation based on work of Wim Boehmer

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