Hello! Welcome back to the capstone project module.
In our last lesson, we established the hydraulic framework for our villa project by grouping all the sprinklers and drippers into logical zones. We determined that our design would need two sprinkler zones and one drip zone to function within our water supply's capacity.
Today, we will refine the physical layout, focusing on the most common challenges in landscape design. This lesson directly addresses the learning outcome: to design a layout for scattered shrubbery using individual drippers and for lawn areas with irregular shapes. As a landscape architect, your ability to create fluid, organic shapes is a great asset. This lesson will give you the technical irrigation skills to water those designs effectively and efficiently.
We will focus on two key areas:
- Sprinkler Placement for Irregular Lawns: Moving beyond simple rectangular grids to achieve perfect coverage on curved and oddly-shaped turf areas.
- Drip Irrigation for Scattered Plantings: Designing a precise, water-wise layout for individual shrubs, trees, and complex planting beds where a simple grid of dripline is not suitable.
1. Mastering Sprinkler Layouts for Irregular Shapes
Your landscape designs will rarely be perfect squares. Curved pathways, deep bedlines, and unique property shapes require a more flexible approach than a simple grid. The goal remains the same: uniform, head-to-head coverage. The method to achieve it, however, is different.
The "Edge Method"
For non-rectangular areas, the most effective technique is the "Edge Method." This approach starts at the perimeter of the area and works inward.
Irrigation Notes: Sprinkler Spacing
The document 'Irrigation Notes: Sprinkler Spacing' by Hunter Industries provides an excellent technical explanation of this technique. While you're familiar with the 'Geometrical Shape Method' for rectangles, we'll now focus on handling curves.
Please read the section titled 'Edge Method' (page 2). Pay close attention to Figure 6, which illustrates the key first step: converting a curve into a series of straight lines based on the sprinkler's radius.
As described in the reading, the process for the Edge Method is:
- Define the Edge: Trace the boundary of your lawn area. For any curved sections, approximate the curve with a series of straight lines. The length of these lines should be roughly equal to the throw radius of the sprinklers you plan to use.
- Place Part-Circle Heads: Place part-circle sprinklers (quarter, half, etc.) at each corner or vertex you've created along the perimeter. Adjust their arcs to match the shape of the boundary precisely.
- Fill the Perimeter: Add more part-circle heads along the straight edges between the corners, ensuring you maintain head-to-head spacing.
- Work Inward: Once the entire perimeter is covered, start placing full-circle heads in the interior. Position these so their spray reaches the heads on the perimeter, again maintaining head-to-head coverage.
- Add "Back-up" Heads: In very complex shapes, you may have small, dry pockets. Don't be afraid to add a smaller-radius "back-up" head to cover just that spot. Ensure its precipitation rate matches the other heads in the zone.
A practical tool for handling these irregular angles are Variable Arc Nozzles (VANs), which allow you to adjust the spray pattern on-site from 0 to 360 degrees.
Designing Landscape Irrigation | DIYers can do it too!
Let's watch a brief clip from the 'Designing Landscape Irrigation' video that highlights the utility of VAN nozzles.
Watch the segment from 09:40 to 10:20. The presenter explains how VAN nozzles are ideal for areas that are not 'rectilinear', such as those with a 'wandering bed line'. This directly applies to the Edge Method.
2. Precision Watering for Scattered Shrubbery
For planting beds with scattered shrubs, individual trees, or mixed perennials, a grid of inline dripline is inefficient, wasting water on bare soil. The professional solution is point-source drip irrigation.
This method uses a solid "blank" supply tube that snakes through the planting area. At each plant, you punch in a fitting and attach a small-diameter spaghetti tube that delivers water directly to the plant's root zone via an individual dripper (emitter).
The Do-It-Yourself Guide to Backyard Drip Irrigation | USU
The 'Do-It-Yourself Guide to Backyard Drip Irrigation' from Utah State University provides a clear breakdown of how to design and calculate for point-source systems.
First, read the section 'New Drip Irrigation Systems' to understand the basic layout of a main supply tube with smaller tubes branching off to individual plants. Then, read the section 'Drip Irrigation - Supply Lines and Emitters', focusing on the description of 'Point source emitters'. This explains the core concept of our design.
Designing the Point-Source Layout
- Route the Main Supply Line: Lay out a ½-inch or ¾-inch blank polyethylene tube, positioning it to pass within a meter or two of every plant you need to irrigate.
- Connect to Individual Plants: For each plant, punch a hole in the main supply line and insert a barbed connector. Attach a length of ¼-inch "spaghetti" tubing, run it to the base of the plant, and stake it in place.
- Install Emitters: Attach a point-source emitter to the end of the ¼-inch tube.
The key advantage here is flexibility: you can give a large shrub three 4-L/h drippers while a small perennial next to it gets one 2-L/h dripper, all on the same zone.
Calculating the Number of Emitters per Plant
How many drippers does each plant need? This depends on the plant's size, soil type, and the desired wetted area (typically 50-60% of the root zone).
The Do-It-Yourself Guide to Backyard Drip Irrigation | USU
Let's return to the USU guide to learn how to perform this crucial calculation.
Read the section titled 'Example Calculations'. Work through the example for the 15-foot diameter tree. Pay close attention to Table 1, which provides an excellent starting point for determining the number of emitters for different plant sizes.
Let's use the formula from the guide for one of our villa's shrubs:
- Scenario: A medium-sized shrub with a 1.5-meter canopy diameter (approx. 5 feet).
- Goal: Wet 50% of the root zone.
- Soil: Loam. From soil charts, we know a 4 L/h (approx. 1 GPH) emitter wets an area of about 0.2 m² (2.1 ft²).
- Calculate Plant Area:
Area = π * (radius)² = 3.14 * (0.75 m)² = 1.77 m² - Calculate Required Wetted Area:
1.77 m² * 50% = 0.885 m² - Calculate Number of Emitters:
Number of emitters = (Required Wetted Area) / (Area wetted by one emitter)
0.885 m² / 0.2 m² per emitter = 4.425
We would round up and use five 4-L/h emitters for this shrub, spaced evenly around its dripline (the edge of its canopy), not at the trunk.
Test your understanding!
You are designing the irrigation for a new tree planted inside a lawn area. The lawn is irrigated with sprinklers. Why is it a bad idea to rely on the lawn sprinklers to water the tree, and what is a better professional solution?
Show answer
It's a bad idea for two reasons:
- Different Water Needs: Lawns have shallow roots and require frequent, short watering. Trees have deep roots and need infrequent, deep watering. Using the lawn schedule would either underwater the tree's deep roots or overwater the lawn, causing disease.
- Trunk Damage: The constant spray from sprinklers on the tree trunk can promote fungal growth and rot.
The better solution is to create a dedicated drip ring around the tree on the drip zone, independent of the sprinkler zone. This allows you to water the tree deeply and infrequently, directly at its root zone, without affecting the lawn or the tree's trunk.
Advanced Technique: Drip Rings for Trees
For trees, especially those located within lawn areas, concentric rings of dripline are an excellent method. This promotes a wide, healthy root system.
Common Dripline Design Layouts
The video 'Common Dripline Design Layouts' from Ewing Outdoor Supply has a perfect segment demonstrating this professional technique.
Watch the clip from 02:08 to 02:51. This shows how to use concentric circles of dripline to irrigate trees, encouraging the roots to expand outward and creating a stronger tree.
Conclusion
You now have the advanced layout techniques needed to handle the complex planting scenarios in your villa project. By mastering these methods, you ensure that every plant receives the precise amount of water it needs, no matter how irregular the landscape shape.
Key Takeaways:
- Irregular Lawns: Use the Edge Method to lay out sprinklers. Approximate curves with straight lines, place heads on the perimeter first, and then work your way into the center.
- Scattered Shrubs: Use point-source drip irrigation. Run a blank supply tube near the plants and use smaller spaghetti tubes with individual emitters to deliver water directly to each plant's root zone.
- Trees in Lawns: Install dedicated drip rings connected to the drip zone to provide deep, infrequent watering that is separate from the lawn's sprinkler system.
In our next lesson, we will begin the final phase of our capstone project: Hydraulics, Scheduling, and Deliverables. We will start by performing the full hydraulic calculations for the most demanding zone in our design, sizing the pipes and calculating friction loss to ensure our system will perform flawlessly in the real world.