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3 CAPTURE RAINWATER FOR ALL LAWN IRRIGATION

This action focuses on eliminating water used for landscape irrigation by using captured rainwater on-site.

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why?

Irrigation of our residential lawns and public spaces accounts for 10% of all water used in Minnesota annually (Minnesota DNR). This is a significant use when compared to the 15% of annual water use that makes up all other residential water consumption (including toilet flushing, showering and all other home use). Luckily, irrigation water consumption has a simple solution: capture rainwater on site and store in rain barrels until needed. In addition to saving water, capturing rainfall to use for irrigation on site has many other pollution and energy reducing affects.

As can be witnessed watching the Mississippi river rise during any rainfall in Minneapolis, all water which falls on densely paved urban areas is quickly transported into rivers and streams via gutters on city streets and storm sewers. After washing over roads collecting oil and pollutants, this water is then rapidly funneled into nearby rivers and streams. It must then be transported to water management facilities to remove the pollutants making it safe to drink. The city of Minneapolis boasts approximately 1,000 miles of water mains in the city, "enough to stretch from here to Denver" (City of Minneapolis).

Lastly, this water is transported back to exactly the locations where the water originally fell as rain.

Even more energy-intensive water management strategies exist in locations such as Orange County, California, an area which has adopted sewage treatment and desalination strategies in order to keep up with a growing demand for water. Sewage treatment required $490 million worth of pipes, filters and tanks for purification (Zimmerman). This process costs $525 per acre-foot (325,851 gallons in an acre-foot), while desalination costs up to $2,000 per acre-foot.

For the sake of comparison, lets consider the cycle of water which occurs naturally. As water falls as rain and lands on vegetated areas, many of the pollutants it captured while falling through the atmosphere are soaked up into plants. It is further cleaned as it seeps through clay, sand and rock into aquifers into the groundwater basin. It is then transported slowly into rivers and lakes, evaporating into the atmosphere. By the time water falls as rain it is clean enough to drink.

In the end, we have created a system of water distribution and cleaning which requires energy to perform all the duties that nature already provides for us, should we take advantage of them. This is a problem of both design and over-consumption. For example, the city of San Diego imports 90 percent of its water, much of it from the Colorado River. With rainfall averages of 10-15"/year, San Diego could dramatically reduce its water imports by capturing rain water.

Many people may be similarly surprised to see the quantity of water which can be collected from rainwater alone. Minneapolis gets 29.3 inches per year of rainfall which is a mid-range average precipitation when compared to the rest of the country. There are many regions of the country which get much less rain (Arizona, Southern California and Nevada), as well as regions which get more, such as the coast of Washington and Oregon. The graphic below illustrates annual average precipitation across the United States.


Precipitation across the United States

Why not take advantage of the 'free' distribution processes of nature? Collecting water on the roofs of homes and businesses requires little to no energy or cleaning and decreases the contamination of fresh water through run-off pollutants.

how to do this action:

Using average rainfall data as well as the square footage of your roof is all that is needed to calculate the amount of rainwater which can be collected on average.

Based on this example, about 90 gallons of water can be captured per day on this roof.




Calculations for rainwater collection


The second part of this action is to evaluate how much water the turf grass in your yard needs and use only that amount when irrigating.

"Many conventional lawns in Minnesota can stay healthy if they receive 1-1.5 inches of water a week, either through precipitation or irrigation. Deep, infrequent watering is generally better for lawns and plants than frequent lighter irrigations, which can cause shallow roots" (Metropolitan Council). Next time you water, place 3 to 5 empty tuna or cat food cans at varied distances from the sprinkler. The time it takes to fill the cans is about how long you should water your lawn (this should take only 15 to 30 minutes).

After calculating how long you should water your lawn, you can calculate how much water is needed for this. An average rule of thumb is 2.15 gallons are used per minute for lawn watering. If the lawn is found to need 20 minute of watering this is 43 gallons.

As you can see from this example home, 90 gallons of water on average are captured on the roof each day and only 43 gallons are needed each time the lawn is watered (which is likely not needed every day). There is more than enough water captured in the rain barrel to meet the need for lawn irrigation.

Following are some additional watering tips from the Metropolitan Council to reduce lawn watering needs further:

  • Water early in the morning to minimize evaporation.

  • Never water faster than the ground can absorb the water.

  • Know your soil and its watering needs.

  • Adjust automatic irrigation schedules at least monthly to ensure water use efficiency.

  • Step on the grass; if it springs back up when you move your foot, it does not need water.

  • Arrange plants in your garden by light and watering needs.

  • Consider drip irrigation systems around trees and shrubs (drip systems permit water to flow slowly to roots, encouraging strong root systems; these systems will also cut down evaporation).

  • Adjust sprinklers to avoid watering sidewalks and driveways.

  • Collect rain water in a rain barrel for watering your lawn and plants.

  • Cut grass no shorter than 2 inches to reduce evaporation and promote deep root growth.

  • Use shut-off nozzles on hoses.

  • Aerate your lawn as needed.

  • When hiring an irrigator, look for a certified landscape irrigation professional.

what will be measured?

KEY QUESTIONS

QUANTITATIVE QUESTION: How much water can be saved by using captured rainwater for all lawn/garden irrigation?

QUALITATIVE QUESTION: How does the experience of capturing rainwater for all lawn irrigation affect your happiness, convenience, health and costs?

BASELINE WEEK TRACKING

QUANTITATIVE
During the baseline tracking week before the project begins, use the corresponding spreadsheet (WTR3_BASELINE) to calculate how much water can be captured from the roof of your house as well as how much water you currently use to water your yard and gardens.

QUALITATIVE


Qualitative Scale

Using the above scale as a visual, rate each of the following criteria on the spreadsheet (WTR3_BASELINE) as it relates to your current lawn/garden irrigation habits:

  • 1. SATISFACTION/HAPPINESS
    (Overall, how much enjoyment or dissatisfaction do you get out of doing and completing this behavior?)

  • 2. CONVENIENCE
    (How easy/difficult and accessible/inaccessible is this behavior for you to do and complete?)

  • 3. HEALTH
    (How healthy/unhealthy and safe/unsafe does this behavior make you feel?)

  • 4. COST
    (How much does this behavior cost? Use positive numbers for being above average and negative numbers for being below average and zero for being average.)

IMPLEMENTATION PHASE TRACKING

QUANTITATIVE
Using the corresponding spreadsheet (WTR3_QUANTITATIVE) to track how much water is used to water your lawn/garden both from your rain barrel and from municipal sources.

QUALITATIVE
Part 1 - Ranking


Qualitative Scale

Using the above scale as a visual, rate each of the following criteria, at the end of the project on the spreadsheet (WTR3_QUALITATIVE). Your answers should not be rated in comparison to your baseline week, but in general as a reflection of how you are feeling.

  • 1. SATISFACTION/HAPPINESS
    (Overall, how much enjoyment or dissatisfaction do you get out of doing and completing this behavior?)

  • 2. CONVENIENCE
    (How easy/difficult and accessible/inaccessible is this behavior for you to do and complete?)

  • 3. HEALTH
    (How healthy/unhealthy and safe/unsafe does this behavior make you feel?)

  • 4. COST
    (How much does this behavior cost? Use positive numbers for being above average and negative numbers for being below average and zero for being average.)

Part 2 - Blogging
Keep a narrative log of your experiences as you implement this action and how it has affected your life. Some of the following questions might be helpful as you reflect upon your experiences.

How big of a rain barrel did you use? Did you find the process of using captured rainwater for watering your lawn and gardens to be easier or harder than your previous habits? What design/infrastructure changes would help you to make this an easier lifestyle change?


resources

Minnesota DNR
ACTION SPREADSHEETS

The spreadsheets referred to above can be found in the Excel file at the following link:

WTR3_Capture Rainwater For All Lawn Irrigation Spreadsheet

If you prefer to enter your responses by hand, printable PDFs of each spreadsheet can be found at the following links (at the end of the project, all data will have to be entered into the Excel spreadsheet):

WTR3_BASELINE
WTR3_QUANTITATIVE
WTR3_QUALITATIVE