Tag Archives: runoff

Rainwater Catchment

Consider Future Demands on Rainwater Collection System

rain-gauge-907678_640When you calculate area rainfall – measured annually, monthly and daily, plus factor in how the water will be used in the future, you can determine how much is storage is necessary to meet your needs.

Being aware of current water use is helpful with knowing how to size a system, but don’t neglect to consider potential future demands. If you’re planning a family, entertaining, have a growing business, or may sell the dwelling and property, you want to account for those scenarios when you calculate storage. At best, the system should be professionally designed and built to meet future demands as well. Here are more reasons to consider future demands when building a rainwater collection system:

Possible drought or longer periods of dry season should also be considered when designing or building a system. Incorporating back up water supplies into a system can be as easy as hauled water, or drawing from a well, community or city water system and should be an available option for those times. Residential rainwater systems in the city are often limited in space for storage, leaving the volume of the cisterns inadequate for year round use. Having the ability to switch to this alternate source can be a necessity in design. However, a more rural environment lends itself to larger storage capacities.

Water demand is an important part of design and the American Water Works Association (AWWA) has conducted a study of various fixtures and appliances. Knowing these demands will help estimate usage and assist the designer to adapt the design accordingly. Single flush toilets use 1.28 gal/ flush, dual flush toilets 1.0 gal/ flush for liquids and 1.28 gal/ flush for solid. Average use is 6 flushes per person, per day. Low use fixtures such as shower heads, faucets, cloths washer (front loading) are recommended for the overall design of the house and can be found in publications from manufacturers.

Outdoor demand should be limited as much as possible. Drought tolerant plantings, drip irrigation, and general conservation will help limit outdoor usage.

For specific irrigation needs, Evapotranspiration (ET) is the measurement of amount of water in inches that is needed to grow plants. All plants have a different watering requirements, also being affected by temperature, wind, humidity, and sunlight. A state climatologist can be contacted to attain an ET standard reference for your area. Careful consideration of outdoor use must be given if irrigation is part of the RWC design. An average city lot can use as much as 1,800 gallons of water for watering a lawn.

In order to get the best performance from your rainwater collection system, indoor and outdoor demands must be carefully calculated using best storage capacities, surplus and defect, level of storage, daily, monthly, and annual use/demand for the entire year. Simply calculating the average annual rainfall amounts will not produce the end goal of a well designed RWC system. It is best to determine average potential of collection and use. Determine average daily, monthly, and annual rainfall amounts. Calculate collection area, and determine runoff. Identify highs and lows of rainfall amounts and demands. Determine those months of low amounts of rainfall along with the carryovers from months prior. Certainly, identify those months of zero rainfall.

When you know how you currently and potentially will consume collected rainwater, plus install water efficient fixtures and by employing best conservation practices, you will have enough during periods of high demand or drought, when you might have to cut back or switch to an alternate source. If you plan for this during the design process, you will have a system that works for you far into the future.

This article was originally published under the title Estimating Water Usage for a Rainwater Collection System at RainBank.info

Commercial Rainwater Harvesting, Rainwater Catchment

How Rainwater Collection Protects Water Supplies

Federal Way Washdown_RainBankLLC_webCan Rainwater Collection Protect Water Supplies?

As mentioned in Ken Blair’s previous article, rainwater collection for residential and commercial construction helps protect our water supplies by using rainwater for irrigation, toilet facility, and other uses.

For example, the city of Federal Way, WA uses a rainwater collection system for its school maintenance facility. It collects rainwater for washing  its school bus fleet, and during the summer, the collected water is used for irrigation.

In Harvesting Nature’s Supply, ARCSA (American Rainwater Catchment Systems Association) board member, Neal Shapiro writes about a city library using rainwater collection for toilet flushing, Santa Monica’s first municipal building to implement rooftop rainwater harvesting for indoor use.

Shapiro, watershed management program coordinator for the Office of Sustainability and the Environment for the city of Santa Monica, CA, goes on to document the library’s rainwater harvesting system, showing  how rainwater can be collected on site for non-potable use in a commercial setting. This approach promotes the use of “local water resources and local self-sufficiency; reduces dependence on imported potable water, which benefits distant watersheds by keeping more water there; and reduces negative impacts from stormwater, which carries numerous pollutants to Santa Monica Bay”.

To read the full article, published on eStormwater.com, please click here.

Rainwater Catchment, Sustainability

Should I Collect Rainwater From My Roof ?

rain-432770_1280There are many good reasons for collecting rainwater from your roof. By doing so, you would be helping to protect our rivers, streams, lakes, sounds, bays, and oceans from pollutants entering these bodies of water through stormwater runoff.

A combined sewer is a type of sewer system that collects sewage and surface runoff in a single pipe system. Combined sewers can cause serious water pollution problems due to combined sewer overflows, which are caused by large variations in flow between dry and wet weather. This type of sewer design is no longer used in building new communities (because modern design separates sanitary sewers from runoff), but many older cities continue to operate combined sewers.

By reducing runoff from our roofs, less water is entering the combined sewer system, reducing amounts of discharge into our bodies of water.

Collecting rainwater from our roofs reduces demand on our centralized water systems.

The overwhelming majority of the water used in the U.S. comes from freshwater supplies of surface and groundwater. Water extracted for public systems is treated to potable standards as defined by the Safe Drinking Water Act. Access to high quality water has greatly benefited public health, but it has also resulted in our current system which utilizes potable water for virtually every end use, even when lesser quality water would be sufficient. In addition to conservation methods, using alternative sources of water will be necessary for more efficient use of water resources.

Rainwater collection reduces electrical usage.

According to the EPA’S Rainwater Harvesting Policies, Municipal Handbook, the connection between water and energy is often overlooked, but the process of extracting water from surface or groundwater supplies, bringing it to treatment facilities, treating it to drinking water standards, and delivering it to residential and commercial customers expends energy – primarily because of pumping and treatment costs. The water sector consumes 3% of the electricity generated in the U.S. and electricity accounts for approximately one-third of utilities’ operating costs. Reducing potable water demand by 10% could save approximately 300 billion kilowatt- hours of energy each year. Water reuse systems, like rainwater harvesting, supplant potable water and reduce demand. The reduced water demand provided by rainwater harvesting systems translates directly to energy savings.

Collecting rainwater provides a safe, clean, reliable source of water and has many benefits available to the consumer.