Water Balance Modeling Techniques

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Water Balance Modeling Techniques
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Overview

• Reservoir basics
• Overflow_Rate, Withdrawal_Rate, changing upper
  bound
• Using Extrema elements to track high and low
  extremes
• Using Status elements to track the status of a
  Reservoir (and control actions such as pumping)
• Using Time Series elements for precipitation and
  other histories
• Using Material Delay elements to simulate seepage
  and flow
• Using Convolution elements to simulate a runoff
  using a unit hydrograph
• Generating stochastic precipitation, evaporation
  and flow histories
• Using Allocators and Splitters
• Using the Reliability Module to simulate
  equipment failure
• Share your own techniques

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Reservoir Basics

• Overflow Rate
• Using the Withdrawal Rate output
• Varying the Upper Bound (to simulate silting up)
• Using an Extrema to track peaks/valleys
• Using a Status element to track status of a
  Reservoir and control actions (such as pumping)

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Using Time Series Elements in Water Balance Models

• Useful for inputting precipitation, evaporation
  and other time series
• Important to
• Differentiate between rates and values
• Differentiate between instantaneous flows and
  averages flows
• Can import data from spreadsheets

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Using Material Delay Elements to Simulate Seepage
and Flow

• Delay Time is mean velocity of flow
• Dispersion can simulate spreading
• Both can be specified as a function of
  hydrogeologic properties
• Both may change with time (e.g., is material at
  field capacity?)

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Using Convolution Elements to Simulate a Runoff
Using a Unit Hydrograph

• A Convolution element converts an input signal to
  an output signal via a transfer function
• You provide an input signal (e.g., rainfall rate)
  and a transfer function (the unit hydrograph)
• The convolution integral applies the transfer
  function and computes an output (e.g., runoff)
• A Delay is a specialized instance of a
  convolution integral

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Generating Stochastic Precipitation, Evaporation
and Flow Histories

• Option1 Build your own Markov (or other) model
  manually
• Option2 Using autocorrelated Stochastics
• Option3 Use the History Generator element

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Splitters and Allocators

• Should be very powerful elements for water
  balance models
• Splitters split (distribute) flows
• Allocators route flows based on specified demands
  and priorities

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Using the Reliability Module to Simulate Pumps
and Other Equipment

• Simulate pump failure, as well as pumps turning
  on and off

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Do you have any favorite techniques that you
would like to share?