The Stochastic Data Import tool (SDI) facilitates incorporating externally generated data into an HEC-WAT FRA compute. The SDI plugin greatly increases the flexibility of HEC-WAT FRA computes by allowing the user to have greater control of the input data – if the Hydrologic Sampler or other event generator plugins are not adequate for a study, a pre-computed set of input data may be used.  This plugin performs two critical functions within the FRA compute: it creates the input DataLocations so that other plugins in the program order can be linked to the input data supplied to the SDI, and it uses the input data to determine the time window for computing each event within the lifecycle.  These functions require specific data formatting of the input data provided to the SDI.  This document also demonstrates how to create an SDI alternative and the components of the SDI alternative editor, and how to incorporate the SDI plugin into an HEC-WAT FRA compute.

A number of studies have used the Stochastic Data Importer to enhance their modeling workflow, and make large-scale hydrologic model computes efficient:

  • A study on non-stationarity effects on reservoir operations used the SDI plugin to feed an ensemble of 160 continuous simulations of inflows for 1950 to 2099 through a HEC-ResSim model of a large watershed to understand impacts of future conditions in the watershed on USACE mission areas within the basin.
  • Numerous studies have used the SDI plugin to feed pre-computed flood events or a large period of record into HEC-RAS models, combined with the HEC-WAT distributed compute plugin to reduce the time to compute all of the events from several months to a couple of days.
  • A study modeling gate failures at reservoirs used SDI to run the same pre-computed scaled events through HEC-ResSim many times while sampling different gate failure conditions.
  • Studies using a "weather generator" approach to sample hydrologic inputs have used SDI to take pre-computed meteorology to feed a HEC-HMS model.


What is this plugin called?

The Stochastic Data Importer plugin has had a few names over the course of it's development.  Due to some challenges with how plugins register with HEC-WAT, the original name Stochastic Hydrologic Data Importer shows up in a few places of the user interface.  For that matter – we don't even want to call it Stochastic Data Importer any more, as a number of places where it has been used are not generating stochastic data.  Think of it as the Static or Structured Data Importer -- bringing in a set of pre-computed (or static) datasets, arranged in a consistent structure  via HEC-DSS files into the HEC-WAT FRA compute, instead of dynamically creating them at compute time.

The name "Stochastic Hydrologic Data Importer" persists for backwards compatibility in two places, the list of models (shown in the first figure below) and as part of the F-part of the DSS records output by the plugin – where it says "StochHydro" as the model name.  Addressing this is planned for the next version of HEC-WAT.