All daily rainfall data was obtained from Environment Canada for 397 stations across Canada, for 55 years, from 1955 to 2010.
Our software automatically selects the geographically closest station to your project site, feel free to view our station list here (Station List)
An essential element in the design of a Rainwater Harvesting System is the water demand. The use of improper water figures can result in either the system being unable to consistently meet daily water demand of users, hence, requiring tank to be top up form trucked water or secondary water supply, or in the case of an over-designed cistern, wasteful capital investment. In either situation it is critical that the water demand value employed in the design process be a representative as possible.
There are two methods to determine the the Water Demand.
- Historical Records - Water records or meter readings that provide an accurate water demand.
- Estimated - We estimate your water demand based on:
- Number of occupants
- Days used per week
The Rainwater Tanks is the heart of the rainwater system and should be carefully selected. We identify the optimal tank size to maximize water savings, when any larger tank would provide only a small additional amount of Usable Rainwater.
Tanks are sized by the following criteria:
- 15%” Dead space” Rainwater harvesting tanks often have unused volume referred to as “Dead space” to account for, undisturbed rainwater at the bottom of the tank, and the head space a the top of the tank.
- Rainfall Collection Loss - Not all rainwater contacting the catchment surface (roof) is collected in the tank, some is lost due to collection loss. Initial loss factor - The initial amount of rainfall loss before collection takes place, Continuous loss factor - the percentage of rainfall that is lost during the rainfall event (due to roof, wind, leaky gutters, etc.)
How does the tank sizing work?
Our software will automatically analyze the useable rainwater from various rainwater tanks, it starts at 1000 liters (cubic meter) and increases by 1000 liters (IE: 1000L, 2000L, 3000L…) The the software compares the useable rainwater for each of these tank sizes, and will determines the useable rainwater Per liter of rainwater storage. By comparing the useable rainwater Per liter of rainwater storage it is possible to determine an “optimum” tank size. When selecting a larger tank it will not provide a significant increase in usable rainwater. The software will continue to increase tank sizes until the largest tank is found that provide a 1% increase in useable rainwater for a 1,000 liter increase in rainwater storage capacity.
What does the report include?
The Rainwater Hydrology Report is 9 Pages and provides a complete picture of the systems hydrology. With breakdowns of all the major sections.
- Cover Page
- Project details
- Rainwater Demand - Indoor
- Rainwater Demand - Outdoor
- Tank Sizing
- Tank Performance Details
- Tank Performance Analysis
- Rainwater Demand Daily
- Tank Overflow analysis
Assumptions Used to Make Hydrology Model and Size Rainwater Tank
The simulation of an operating Rainwater Harvesting system through the use of the computer software was performed while making some assumptions. The following list the assumption associated with the software projections.
- The rainfall data obtained from Environment Canada are assumed to be both accurate representation of historical rainfall patterns and an indicator of future trends.
- The initial and continuous loss factor are assumed to be accurate.
- Snowfall will accumulate on the roof surface we assume a continuous loss of 50% for snow melt that is collected in the rainwater tank.
- The model assumes a uniform rate of daily household water consumption for the winter months and possibly a separate rate for summer months.