Step-by-Step Guide

Site Overview and Controller Configuration

This site is a Fortune 500 company headquarters in Seattle, Washington, featuring a total of five controllers: four BaseStation 3200 units managing the landscape irrigation and one BaseStation 1000 dedicated to a rooftop garden. The hydraulic setup is straightforward, with each controller operating independently on a one-to-one configuration—one water meter, one master valve, one flow sensor, and one controller per system.

Because the main lines and points of connection are completely separate with no interlinking between controllers, this site does not require a FlowStation. A FlowStation would only be necessary if multiple controllers shared water sources or if there was potential for conflict when one controller attempted to access water while another was in use. For simple hydraulic configurations like this one, keeping the system straightforward is the best approach.

Understanding Site-Specific Microclimates

The building architecture creates several distinct microclimates that require different irrigation strategies. The headquarters features extensive curved glass surfaces that create reflected glare onto turf areas below, resulting in zones that receive significantly more heat and light exposure than others. Additionally, courtyard areas and spaces beneath bridges remain shaded and may not receive rainfall at all.

Wind patterns also affect water distribution across the site. Rain coming from the west may leave the east side of the building relatively dry, depending on prevailing winds. These factors—reflected light, shade, and rain shadow—all create unique watering needs that must be addressed through programming.

Leveraging Multiple Programs for Microclimate Management

The BaseStation 3200 offers 99 different programs, which should be fully utilized to address the various microclimates on this site. Rather than lumping all turf areas into a single program, separate programs should be created for turf exposed to additional sunlight from reflected light versus turf on the opposite side of the building that remains shaded.

This approach allows for independent scheduling and water management for each microclimate. Even when using timed watering (without sensors), different programs can run on different schedules to accommodate varying water needs. This strategy eliminates the need to compromise by applying the same watering schedule to areas with different requirements.

An important advantage of the BaseStation system is that having multiple programs does not create scheduling conflicts or hydraulic problems. When the system is configured correctly with proper flow learning, the controller will run programs concurrently based on available hydraulics. The limiting factors are the size of the hydraulics and the available water window, not the number of programs. The controller manages flow automatically, allowing you to take full advantage of available water capacity within your watering window.

Implementing Soil Moisture Sensors in Landscape Areas

For landscape areas, soil moisture sensors should be deployed using a lower limit watering strategy. In the example configuration, a soil moisture sensor is assigned to zone 25, which serves as the control zone. All other zones in that hydrozone are then linked to zone 25 and its associated sensor, meaning the sensor reading from zone 25 influences when all linked zones will irrigate.

Critical sensor placement principle: Always install the sensor in the "good" control zone—the area with typical, representative conditions—not in the problem zone. A common mistake is placing the sensor where the landscape is always wet or always dry, hoping the sensor will fix the problem. Instead, place the sensor in the area with normal drainage, typical exposure, and good plant health, then use other programming tools to compensate for problem areas.

Using Tracking Ratios to Fine-Tune Microclimates

Once zones are linked to a control sensor, tracking ratios provide an additional tool for addressing microclimates and problem areas within the same hydrozone. The tracking ratio adjusts the runtime for individual zones relative to the control zone.

For example, if zone 25 (the control zone with the sensor) is scheduled to run for 45 minutes:

• Zone 27 with a tracking ratio of 90% will run for approximately 40 minutes (90% of 45 minutes)
• Zone 30 with a tracking ratio of 105% will run for approximately 47 minutes (105% of 45 minutes)

This allows you to reduce watering in areas that tend to stay wet or increase watering in areas that dry out faster, all while maintaining sensor control over the entire hydrozone. Tracking ratios can also compensate for known system inefficiencies, such as zones without head-to-head coverage that require longer runtimes, or zones on slopes with different drainage characteristics.

The best practice is to leave the majority of zones at 100% tracking ratio and only adjust the few problem zones up or down as needed, rather than adjusting all zones and potentially creating new imbalances.

Sensor Calibration Options and Strategies

In BaseManager, you have three calibration options for soil moisture sensors: Auto Calibrate, Calibrate Once, or Never. Understanding these options is essential for proper sensor setup.

Calibration primarily determines field capacity—the maximum amount of water the soil can hold after excess water has drained away. This is a measurable point. The dry-down or depletion threshold is set by the user based on plant needs and site conditions, but field capacity must be accurately established first.

Manual observation method: For new construction, contractors can install the sensor and observe soil moisture levels over time, manually setting field capacity based on what they observe after irrigation events. This approach works well when you have time to monitor the system and make adjustments.

Auto Calibrate method: This unique feature automates the field capacity determination process. When you select Auto Calibrate, the system operates similarly to upper limit watering during the calibration period:

1. On the first scheduled irrigation cycle, the system waters for the programmed runtime and monitors whether the sensor reaches field capacity.

2. If field capacity is reached, the system automatically sets that level as the calibration point and establishes a lower limit threshold (typically 20-25% below field capacity) as a safety set point.

3. If field capacity is not reached during the first cycle, the next scheduled irrigation will run for the programmed time plus an additional 20% to push more water to the sensor.

4. This process repeats, adding 20% more water each cycle, until field capacity is detected and calibration is complete.

The calibration process may take several days depending on irrigation frequency, and you may observe longer-than-expected runtimes during this period. For example, if you programmed rotors for one hour but the distribution uniformity or application rate wasn't sufficient to reach field capacity, the next cycle might run for 80 or 90 minutes. This is normal behavior—the system is working to push enough water to the sensor to establish the proper calibration point.

Upper Limit Watering for the Green Roof

The rooftop garden features shallow-rooted sedums planted in a growing media that dries out much more quickly than field soil. This makes it an ideal candidate for upper limit watering rather than lower limit watering.

With upper limit watering, the system irrigates every scheduled water day, running until the soil reaches field capacity, then shuts off. The zone will not necessarily run for the entire programmed runtime—it runs only as long as needed to bring the soil up to field capacity. This strategy ensures the shallow growing media is regularly replenished before it becomes too dry, which is critical for the health of shallow-rooted plants in a rooftop environment.

The choice between upper limit and lower limit watering is a tool that should be selected based on the specific needs of the site, the plant material, the soil or growing media characteristics, and the water management philosophy of the landscape manager. There is no universal rule that certain applications must use one strategy or the other—athletic fields, green roofs, and other specialized areas can be managed with either approach depending on the desired outcomes.

Seasonal Adjustments to Sensor Thresholds

Sensor thresholds often require seasonal adjustment based on plant stress levels and environmental conditions. In spring, when nights are cooler and plants are not heat-stressed, turf and other plants can typically tolerate drier soil conditions. The depletion threshold can be set lower, allowing the soil to dry out more before triggering irrigation.

In summer, when temperatures are high and plants are under greater stress, the same plants may require a higher threshold (less depletion) to maintain health. These seasonal adjustments should be made based on observation of plant health, temperature patterns, and site-specific stress factors.

Proper Sensor Installation on Slopes

Correct sensor installation is critical for accurate readings, especially on sloped terrain. Sensors must always be installed vertically, like a knife cutting into the soil, never horizontally or flat against the ground. Installing a sensor flat can cause water to pool on the sensor blade and create cooling effects that result in erroneous moisture readings.

On slopes, the sensor should be oriented parallel to the direction of the slope (up and down the slope) rather than perpendicular to it. This prevents the sensor from acting as a dam that causes water to accumulate against the sensor blade as it moves downhill. The orientation of the sensor—whether the black portion with the biCoder faces uphill or downhill—does not matter for performance.

Managing Runoff with Intelligent Cycle and Soak

The site includes sloping landscape areas that meet hardscape surfaces, with a water feature nearby. This configuration creates significant risk for runoff, which could carry fertilizer, grass clippings, and other contaminants into the water feature. Intelligent cycle and soak programming is the solution for managing this runoff risk.

To set up cycle and soak:

1. Determine the total runtime needed for each zone based on plant needs and system precipitation rate. In this example, spray head zones require between 9 and 12 minutes of total runtime.

2. Determine the cycle time—the maximum amount of time water can be applied before runoff begins. This is best determined through field observation: turn on the zone and watch how long it takes before water begins running off the slope. In this example, the cycle time is set at 4 minutes, meaning runoff begins around 5 minutes of continuous watering.

3. Set the soak time—the period between cycles that allows water to penetrate the soil. In this example, a 45-minute soak time is used between cycles.

4. The controller automatically calculates the number of cycles needed. For zone 94 with a 12-minute total runtime and 4-minute cycle time, the system will run three 4-minute cycles with 45-minute soak periods between them. For zone 98 with a 9-minute total runtime, it will run two 4-minute cycles and one final 1-minute cycle to complete the total.

A critical advantage of the BaseStation system is that during soak periods, the controller looks for other zones to run, maximizing the use of available water and hydraulic capacity. While zone 94 is soaking, the system can run zone 95, and while zone 95 is soaking, it can run zone 96. This keeps water flowing continuously through the system rather than having idle time, which would extend the total watering window unnecessarily.

Research shows that once runoff is initiated during an irrigation cycle, 80% of the water applied after that point is wasted—it does not reach the root zone. Cycle and soak prevents this waste by keeping application rates below the soil infiltration rate.

Setting Up a Salt Leaching Program

Due to the site's waterfront location with offshore breezes and potential tidal influences, salt accumulation in the soil is a concern. Salt-sensitive plant material may show burn symptoms or decline in health if salts are not periodically flushed from the root zone.

A dedicated leaching program can be set up to address this issue:

1. Create a separate program specifically for salt leaching (in this example, Program 99 is designated as "Salt Leaching Rotors").

2. Keep this program disabled when not in use, enabling it only when leaching is needed—typically quarterly or annually depending on site conditions and plant response.

3. Set runtimes at 2-3 times the normal irrigation runtime to ensure sufficient water volume moves through the soil profile to flush out accumulated salts. In this example, a 90-minute runtime is used for leaching, compared to typical irrigation runtimes of 30-45 minutes.

4. Combine the leaching program with cycle and soak to prevent runoff during the extended watering period. Applying 90 minutes of continuous water would cause significant runoff, but breaking it into cycles with soak periods allows the large water volume to penetrate the soil effectively.

An advanced approach would be to connect an EC (electrical conductivity) meter with a 4-20 milliamp output to a 4-20 milliamp biCoder on the BaseStation system. This would allow you to create a start, stop, or pause program based on actual soil salinity readings, automating the leaching process based on measured salt levels rather than a fixed schedule.

Spring System Preparation and Verification

As the irrigation season begins, it's essential to review and verify all programming and configuration settings. The settings that were appropriate for the previous fall may not be suitable for spring startup after winter dormancy.

Key areas to review include:

Water source settings: Verify that water source, control point, and main line settings are correctly configured. These settings are frequently missed during installation or only partially completed, which can result in master valves that never close or other hydraulic management issues.

Flow learning: Consider relearning flow for the site. Soils may have settled over winter, plants have developed more root mass, and irrigation systems may have shifted. Relearning flow ensures the controller has accurate data for managing hydraulics throughout the season.

Sensor recalibration: Evaluate whether sensors should be recalibrated for the new growing season. Soil conditions change over time, and recalibration ensures accurate field capacity readings.

Program review: Examine all active programs to ensure they're appropriate for spring conditions. Adjust sensor thresholds, runtimes, and schedules based on current plant needs rather than carrying over settings from the previous season.

Data analysis: Review data collected from sensors during the winter months. This historical data can reveal patterns and inform irrigation strategy decisions for the upcoming season, helping you optimize water use and plant health.

Taking time to properly prepare the system for the new irrigation season will greatly impact system performance and efficiency throughout the growing season.

Video Walkthrough

Video originally published March 2021.

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