Help file has not been fully updated.

New 2015 Feb

Diffusion or routing of rainfall is added. DWF is added. Routing works by spreading rainfall pulse evenly to a number of timesteps. For example, a rainfall pulse of 1 inch can be spread to 30 minutes. If each timestep is 5 minutes, each timestep gets 1/6 inch of rainfall mass. Superposition of such spreading of each rainfall pulse effectively provides routing of the runoff to the storage tank.

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The diffusion time step should be greater than 1. If no routing is needed, use 1 as default value.

Average dry weather flow is added to rainfall. No routing of DWF is needed.


Mass Balance Model

"essentially, all models are wrong, but some are useful", George E. P. Box

Mass balance calculation of timeseries data, such as rainfall, is conceptually simple. However, it has to be implementation in softwares that are difficult to comprehend or time consuming to set up. The attempt here is to make it available in a browser environment. There are minimum input parameters; yet the results are useful.


Storage, Pump, Overflow Calculation


Mass balance calculation for each timestep is performed. No hydraulic routing is used.
Pseudocode: Inflow = R*C*A Loss = R - Inflow if Inflow + S > Pump Capacity Pumped = Pump Capacity Balance = Inflow + S - Pumped if Balance > Storage Capacity Overflow = Balance - Storage Capacity Balance = Balance - Overflow else Overflow = 0 Balance = Balance endif else (Inflow + S < Pump Capacity) Pumped = Inflow + S Overflow = 0 Balance = 0 endif Terminology All terms are volume, except R is depth S'= Storage Capacity S = Balance R = Rain I = Inflow P'= Pump Capacity P = Pumped O = Overflow

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  1. Select rainfall
  2. Select
  3. Output
  4. Click Buttons


  1. Overflow
  2. Rainfall Events
  3. Tips
  4. Extra


FOB - Federal office building raingauge

CSV - Comma separated variable file

Avg Annual - a rainfall data for SF

Design Storm - Rainfall hyetographs for SF


Data Format

Rainfall data must be space or tab delimited like this:
Comment can be added like this.	
11/14/1979 17:05 0
11/14/1979 19:35 0.12
11/14/1979 20:15 0.24
11/14/1979 20:20 0.24
11/14/1979 20:25 0.12
11/14/1979 22:50 0.12
11/15/1979 3:45 0
11/15/1979 7:30 0.12
11/15/1979 7:35 0.12
11/15/1979 7:50 0.12

Choronologic order is not necessary.
Timesteps without rain can be excluded or included.
Lines not beginning with a digit character will be ignored as comments.

For example, the data above along with this text
 can be copied into the text area without any issue.


Use at your own risk

Chart for long duration takes longer

Use 3 decimals for accumulated plot

Sanitary flow is not implemented yet.

Firefox Only

Contact :

copyright BS 2013

Updated 2014 Oct