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To properly capture water flow from rainfall, you need to assess where it naturally flows first. Photo: Tae Wook, Creative Commons License

Where Does Water Flow in Your Landscaping?

To capture rainwater and any excess irrigation inthe soil or rain barrels, it is first necessary to understand what happens when water comes off the roof of buildings and moves across the property.  

Where is water moving? 

Make a copy of your landscaping site plan, and label it “Water Plan.” It should have the position of the buildings and major landscaping structures. During a rainstorm, watch what happens to water as it comes off the roof of the house and moves through the property. 

  • Are there any low spots where water pools? 
  • Does water run entirely off the property anywhere? 
  • Do any buildings or hard surfaces such as patios appear to be damaged by water? Is the damage caused by rain, by irrigation, or by both?

Note the direction water moves around the property from one area to another, or through multiple areas. 

Turn on irrigation systems for three minutes, and make a note about where there is any pooling or runoff.  

Assess the downspouts for water volume

Use the following process to figure out how much water comes off any hard surface, whether it is a roof, patio, driveway, or sidewalk. 

First, imagine the total roof area of your garage is 20 by 20 feet square, or 400 square feet, and water flows off it in two downspouts.  

If half the water goes into each downspout, the roof size for one downspout is half your total area. In this example, that is 200 square feet. 

Multiply the square footage for your downspout area by 0.62 to get the gallons of water per inch of rain coming from your downspout. Using our example of 200 square feet, the formula is 200 x 0.62 = 124 gallons.  

Once you have this number, you can plan for the resources needed to capture this water runoff for later use using tools such as rain barrels.  


This article was inspired by the 71-page Sustainable Landscapes Program guidebook available at The Water Authority and its partners also offer other great resources for landscaping upgrades, including free WaterSmart classes at 




OPINION: Gov. Newsom must mop up Brown’s water mess

Despite many high priority issues on his plate, one of Gov. Gavin Newsom’s first tests will be how he deals with California’s water challenges and opportunities. Unfortunately, in the last days of his term Gov. Jerry Brown made a bad bargain with the Trump administration and special interests. It’s yet another mess for the new governor to mop up. During his last month, Brown quietly signed an agreement with the Trump administration to transfer water from Southern California and portions of the Bay Area to corporate farms in the San Joaquin Valley.

New Scale Will Measure Atmospheric Rivers In California From 1 To 5, Like Hurricanes

Marty Ralph was sitting in a San Francisco restaurant a couple of years ago when the morning forecast came on the TV, showing the typical weather symbols indicating what the week ahead would bring: a sun, a cloud, a rainy cloud and a darker, more ominous rainy cloud. Ralph, the director of the Center for Western Weather and Water Extremes, knew that at the end of the week, an intense atmospheric river storm was coming through the area. But he didn’t think the TV meteorologists could convey that very well with the icons on the screen. So he and a team of researchers got to work creating a ranking system that would be more helpful.

Will Trump’s California Water Plan Send More To Republican Farmers And Short Democratic Cities?

While campaigning for president in 2016, Donald Trump promised a cheering Fresno crowd he would be “opening up the water” for Central Valley farmers who’d been victimized by “insane” environmental rules to protect fish. Trump took one of the most aggressive steps to date to fulfill that promise Tuesday by proposing to relax environmental regulations governing how water is shared between fish and human uses throughout the Central Valley. The U.S. Bureau of Reclamation released an 871-page “biological assessment” of conditions in the Delta that it said is designed to “maximize water supply and delivery” while maintaining protections for fish.

All Yosemite Roads Closed; 7 Feet Of New Sierra Nevada Snow

All roads in and out of Yosemite National Park were closed Tuesday due to heavy snow and fallen trees, following four days of winter storms that blanketed the Sierra Nevada mountains. Some ski resorts near Lake Tahoe received 7 feet or more between Friday and Tuesday morning. “We’ve had incidents throughout the park,” said Yosemite spokesman Scott Gediman. “We’ve had trees come down. We’ve had vehicles slide off the road. Power is out at Wawona.” Gediman said all hotel reservations for Tuesday evening have been cancelled. The park’s ski area at Badger Pass also was closed Tuesday.