Available translations: English

About PDM

The Probability-Distributed Model, or PDM, is a general conceptual rainfall-runoff model which transforms time-series of rainfall and evaporation to river flow at the catchment outlet (Moore, 1985, 1999, 2007). 

The model formulation is based on a probability-distributed moisture store and translation of runoff and drainage via routing stores. 

A schematic of the Probability Distributed Model (PDM)
The Probability Distributed Model (PDM)

Hydrological Applications

The PDM is used for operational flood forecasting across the UK and abroad. It has been applied to a wide range of hydrological studies including climate change impact (e.g. Kay & Jones (2012)Kay et al. (2020)), water resource management (e.g. eFLaG) and modelling ungauged locations (e.g. Kay et al. (2007)).

Methodological developments include enhanced groundwater representation (Moore & Bell, 2002), inter-catchment water exchange and multi-zone functionality for modelling mixed urban/rural catchment responses and higher/lower rainfall areas.

PDM Functionality

The PDM software is available under licence in two forms:

  • PDM for PCs. A Windows-based application for interactive model calibration and assessment.
  • UKCEH XML Module Adapter. An executable module for use in operational flood forecasting systems (e.g. Delft-FEWS) and for batch processing on Windows and Linux systems.
PDM for PCs screenshot showing a model hydrograph
PDM for PCs screenshot showing hydrographs of modelled and observed river flow

The PDM software has the following features:

  • model toolkit to represent a variety of catchments
  • choice of time-step, such as 15 minutes and daily
  • choice of instantaneous or accumulated flows
  • forecasts created using state-updating or error-prediction methods
  • comprehensive manual

In addition, the PDM for PCs calibration application has the following functionality:

  • automatic and interactive calibration facilities
  • graphical user-interface
  • output to Excel and other graphical tools
  • automated event selection
  • performance assessment of threshold-crossings and flood peaks
  • wide range of statistical analyses
PDM for PCs: flood peak performance assessment
PDM for PCs: flood peak performance assessment

Contact for further information

For further information on PDM, please contact Bob Moore via the ForecastModelSupport@ceh.ac.uk email.

Bob Moore
UK Centre for Ecology & Hydrology
OX10 8BB
United Kingdom

Telephone: +44(0)1491 692262

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