NotchFlow
Water flowrate calculator
By using a simple height measurement, NotchFlow can calculate the flow of water over a specially
crafted VNotch weir, and through WHO recommendations estimate the number of people that the flow could support.
NotchFlow is available in the iTunes store and you can find out more about it on my blog.
Being able to easily determine the flowrate of a water source is important for many situations. For example
a farmer may want to know how much water he has available for his crops, while an aid worker may want to know how many people
could be supported from a given spring. However when you are out in the middle of the countryside is is very likely that you will have
little in the way of tools to help you measure a flowrate. But this is where NotchFlow comes to the forefront!
The NotchFlow program is designed to help people estimate the flowrate of a water course from a single height measurement.
It works in conjunction with an easy to construct VNotch weir that funnels all the water through a well defined
Vshaped profile. This geometry simplifies all the calculations and only requires the height of the water above the bottom of the
VNotch to be measured in order for NotchFlow to determine the flowrate.
The program is easy to use and contains all the information required to guide the user in the field in how to construct
the required weir, full details on how the calculations are performed and references to external material that further expands on
measuring flowrates and the health aspects of potable water usage.
Here is a selection of some of the screens from NotchFlow:
Calculations

Preferences

Information

Weir Design

The Calculations screen shows a flow rate and supported population being calculated from a measured height value.
But NotchFlow supports three variations of this calculation:
 Calculate flowrate and supported population for a given water height.
 Calculate supported population and water height for a given flowrate.
 Calculate water height and flowrate required to support a given population.
The Preferences screen allows several items to be preset for the calculations. All of the preferences can be changed at any time and NotchFlow will
simply recalculate the results based on the current data:
 Units selects between three different units systems: Metric, Imperial and US.
 Profiles selects one of five predefined per capita daily water consumption profiles that are based
on World Health Organization usage patterns. These profiles are used to determine the supported population numbers
from a given flowrate.
 Notch Angle specifies the actual notch angle used in the weir under consideration.
The Information screen provides extended details on several areas:
 The main formulas used to perform the calculations.
 A reference design for a suitable VNotch weir.
 A summary of World Health Organization (WHO) water quality criteria and an explanation of the per capita
water profiles used by NotchFlow.
 Links to external references on weir design and the WHO water quality criteria.
 Version information of the currently installed NotchFlow program.
The Weir Design screen is an example of the depth of information that is available in the NotchFlow program.
