Rainwater Collection & Harvesting Systems
harvesting
systems - design
installation - service
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Rainwater Collection & Harvesting Systems harvesting
systems - design
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Your total potential water capture can be calculated using the following simple formula:
The total amount of water you can collect from your roof depends on 3 things:
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Typical Rainfall and Water Collection Amounts of the BC Gulf Islands
** Catchment From a 1000 sq. ft. roof at 75% The Mediterranean climate (wet winters and dry summers) of the Gulf Islands varies dramatically between different islands. For example a house with 1000 square feet of roof area on Saturna Island would collect 12,900 gallons in a year with average rainfall (Assuming a 75% capture ratio) while a similar house on Bowen Island would collect double that amount. Remember - that every year has a different rainfall pattern. For example the Environment Canada forecast for 2005 - 2006 for the Gulf Islands and the Lower Mainland is a wetter than normal October, November, December. The outlook for winter and spring 2006 is drier than normal, and the summer is projected to be normal to below normal. |
| When calculating the amount of water you need, seriously consider what you want your system to do, and add conservation measures that fit your lifestyle. Consider your indoor and outdoor water requirements separately. |
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Indoor Water Use Calculate your total and monthly indoor water use. Many of the water districts in the Gulf Islands report use levels of 50-60 imperial gallons per person per day (G/P/D) for full time resident households. Rainwater dependent users consider 35-40 G/P/D a maximum, and some are as low as 25-30 G/P/D. Cottage/cabin users are typically in this range. If you are looking at your unique indoor water use patterns consider:
Indoor water conservation can be achieved by a combination of fixtures, appliances, and water conserving practices. Some water conserving aids require user action - such as turning off the water during teeth brushing and shaving; washing vegetables in a pan rather than under a stream of water; keeping a pitcher of water in the fridge rather than waiting for cold water to arrive from a faucet. Beware of the big soaker tub baths. Shower or bath together. To do your own calculations, consider that studies show indoor water use is accounted for in the following manner:
For a rainwater dependent household, water saving appliances can pay for themselves in one or two years because they reduce the size and the capital cost of the cistern (ie. less water needs to be stored). Low flush toilets (3 to 6 litres per flush), can lower indoor water use by as much as 15% and pay for themselves in a year by reducing storage requirements. Other water-saving appliances include - faucet aerators and efficient showerheads, low water use dishwashers, and washing machines, on-demand hot water units and composting toilets. For example, low flush etc... Outdoor Water Outdoor water use can be double your indoor use during the summer. Guidelines for determining how much water you use outdoor:
Consider your unique outdoor water uses:
The greatest savings (up to 50%) are achieved by selecting drought tolerant and native plants and setting up drip watering systems. How Much Water Do I Need to Store For Summer Water storage is the heart of a rainwater system - especially given our dry summers. To determine your minimum water storage requirements combine your monthly demand with the monthly rainfall in your area and the size of your roof. Storage size must be sufficient to get you through the dry summer months. The drier the summers and the higher the summer use - the larger the cistern required. How to Calculate Your Storage Needs The Rainwater Connection uses a Water Balance Table computer program that helps determine the minimum cistern size required to get through the summer in your area. This table combines your monthly rainwater capture, water usage, and calculates the amount of water in your cistern at the end of each month. Information required to calculate your rainwater storage needs:
Minimum Catchment Areas & Cistern Sizes in the BC Gulf Islands Different Gulf Islands and parts of Vancouver Island have different rainfall amounts and patterns. This changes the amount of roof area and the size of cistern required for a two person household to be fully dependent upon rainwater. The following table is based on 100% indoor use for a 2 person conserver household 160 Litres (35 Imp. gal) / Person / Day.
Summer garden water production also changes dramatically. On Salt Spring Island a 2,400 gallon tank would provide about 8,500 gallons of summer gardening water in a typical summer. The similar figures for Bowen Island, with almost twice the rainfall, would be about 12,000 gallons of summer garden water from a 2,400 gallon tank. |
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| Next - What are the basic components of a Rainwater Collection System? | |||||||||||||||||||||
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Phone:
250-246-2155 E-mail: info@rainwaterconnection.com |
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| Copyright The Gulf Islands Rainwater Connection Ltd 2006 | |