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MMWD Blog: Think Blue Marin

Welcome to our blog! Written by staff at MMWD, “Think Blue Marin” explores all things water in south and central Marin—water supplies, conservation, new projects, watershed management, and more.

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Aug 09

A Weather Station from Space

Posted on August 9, 2018 at 2:22 PM by Ann Vallee

by Christina Mountanos

Last month a few of us in the Water Conservation Department journeyed out to the far end of the driving range at Peacock Gap Golf Course for a quick refresher on how to care for our California Irrigation Management Information System (CIMIS) weather station. We met with a representative from the Department of Water Resources (DWR), who recently equipped the core of the weather station with a new data logger, and upgraded some of its other measuring components, too.

Our field trip made me realize that we often reference evapotranspiration (ET) in our Weekly Watering Schedule blog, but seldom mention how it’s actually measured and, specifically, how MMWD measures it. See the picture below and you’ll see the stately, robotic-looking weather station that does just that for us. The technology behind it is very cool, and it’s always a treat to physically visit the site; it’s fun for me to explore this particular technical aspect of our job.

As you may know, evapotranspiration (the combined amount of water that evaporates and transpires from soil and plants) is dependent on five main factors: solar radiation, temperature, humidity, wind and precipitation. Accordingly, our CIMIS weather station has devices that measure each of these factors. For example, the contraption that looks similar to a beehive is what measures temperature and humidity. (You may see a mini version of this if you have a smart controller with its own weather station.) The arm with a flat metal plate at its end has a device on it that measures solar radiation, and it’s called a pyranometer. The arm just behind and below that with the cupped, spinning component—an anemometer—measures wind speed. Finally, the cylinder/funnel-shaped piece of equipment that sits high up on the station measures rainfall. All of these components need regular cleaning and care to ensure they are measuring accurately and transmitting the correct data, hence our recent refreshment training. (You might also notice the solar panel on the base, which is what powers the station.)

The CIMIS station collects data daily and the data is uploaded online. Each week before sending out the Weekly Watering Schedule, we tally daily ET amounts from the CIMIS website, total them together (for a weekly total) and then plug them into special equations that determine suggested minutes for watering. In a nutshell, that’s the process.

And, just to leave you with a couple of last notes that you may find interesting: To measure accurately, CIMIS stations need to be placed in an open area (where buildings or trees will not affect wind speed), on top of maintained, cool-season grass. This is why stations are often located on golf courses. MMWD’s station is actually part of a much larger collection of about 145 weather stations in California, all managed by DWR since 1985, and created in an effort to encourage smarter irrigation practices. 

If you’d like to learn more about CIMIS and other details about the California network of weather stations, you can read more on the official CIMIS webpage

I hope you find this technology as interesting as we do!

CIMIS station
Aug 03


Posted on August 3, 2018 at 10:37 AM by Ann Vallee

by Charlene Burgi

The proverbial saying that “the proof is in the pudding” comes to mind as we monitor our irrigation systems during the heat of summer. During this time of year, dry spots may appear in our lawns or other groundcovers, or we may see tender plants wither or wilt due to lack of water. 

Without uniform distribution, some parts of the garden cannot get adequate water from our irrigation systems. And in trying to reach those dry areas, we end up flooding other areas and wasting water to compensate for a poorly designed system.

 Using ag risers for unblocked head to head coverage
Using ag risers for unblocked
head-to-head coverage
What does a good irrigation design look like? Appearance is easy to describe. Irrigation heads on each station or valve need to be installed so the water from one sprinkler head will reach out touching surrounding sprinkler heads. However, the calculations of friction loss through pipes, and numbers such as gallons per minute, water pressure and elevation changes are but a few of the hidden secrets that equate to good irrigation design.

For example, the aforementioned head-to-head coverage may look adequate from above the ground, but if the water pressure is lacking to push the water the distance needed to reach the other heads, the design will fail. Or, there may be adequate pressure but too many heads on one valve. As a result, the valves need more gallons per minute than the pipes can deliver, causing the water to fall short of the other targeted sprinkler heads.

Another fatal flaw in irrigation design is mixing different types of irrigation on the same valve. One common mistake I see is drip spray heads on the same valve as drip emitters. Drip sprays apply water measured in gallons per minute (GPM) while drip emitters discharge water measured in gallons per hour (GPH). By mixing the two methods of irrigation on the same valve, some plants will be flooded with GPM while other plants will be starved for water dribbling out in GPH.

The same holds true for overhead spray systems. The goal is to have the overhead irrigation sprays provide an equal gallons per minute to the area they are covering. We call this having matched precipitation rates. This can only be achieved by using the same model nozzles on the same valve. For example, mixing an impact head with a rotor on the same valve would be a disaster for the plants: Given the same pressure, a rotor will emit roughly three gallons of water per minute and an impact head will throw out over five gallons of water per minute. You can see how under this scenario some plants will lack water while others get too much. This mix-and-match problem can even occur by using the same type of spray heads but from different manufacturers.

In essence, poor irrigation system designs equate to water waste, not to mention the stress placed on your plants. Take a walk in the garden with your sprinklers on to see how well your system is working. While you are at it, check for broken lines, missing emitters and nozzles that are spraying in unintended areas. Correct the problems and you will find your efforts reflected in lower water bills and happier plants!

I will be off line next week casting a fly into the beautiful lakes above Kamloops. I promise to share more about the beauty of native plants in British Columbia upon my return. Until then, ciao!

Jul 27

A Good Soak

Posted on July 27, 2018 at 10:16 AM by Ann Vallee

by Charlene Burgi

A good soaking always feels refreshing whether it be in a hot tub or pool. The effect can leave us feeling renewed, as water often does in its various uses.

Our container plants rarely get this kind of soaking, where the whole pot or container is submerged into a bath of water covering the soil level. When your container plants are treated to this activity, you will find trapped oxygen bubbling up allowing the soil to absorb the cool water in all parts of the container.

A few weeks ago, I decided to give my tried-but-true houseplants a respite from the summer heat. I filled a bucket deep enough to cover the biggest container, then added just a hint of organic fertilizer for good measure. Each plant took a turn in the bucket. Once the pot stopped bubbling and reached saturation, I moved the plants onto a tray to collect excess water from the drain hole. (Before attempting this exercise, be certain the container has bottom drain holes.) 

The next step required some cleaning. Plants not only like a soaking, but also love showers to remove the dust of everyday living from their leaves. This can be as easy as placing them on the floor of your shower or using a clean microfiber cloth dampened with a solution of castile soap and water. After their shower, shake off the excess water on the leaves. Removing dust and dirt from the leaves allows for better absorption of light for photosynthesis. It also allows for better inspection to spot any insects such as aphids, scale or mealybugs that may have taken up hidden residence in the foliage.

 Spathiphyllum in bloom
 Spathiphyllum in bloom
It took the better part of the day for my fourteen houseplants to complete their spa day. However, the rewards for this effort came back to me tenfold. The peace lily (Spathiphyllum) provided two beautiful flowers this week. It has been years since it’s shown any sign of blooming. The orchids began growing new spikes with the promise of new color appearing within a few months. Even the cactus and jade plant looked perkier!

If you find a few extra hours on your hands, you might consider giving a treat to these oxygen-producing, carbon-dioxide absorbing wonders in your home. If your houseplants have gone the way of a ‘70s fad, you might consider bringing in a few low-maintenance varieties such as pothos, which takes low light, or let that peace lily show off its white flag. The rewards are numerous.