The Ups and Downs of Slope Irrigation
Posted in Irrigation on March 22, 2015
How do you handle slope irrigation?
Keeping plants watered at the proper level offers enough of a challenge already; now throw in landscaped slopes. The challenge just went to the next level. If you over-water, your hillside faces possible erosion. If you under-water though, nothing grows. What to do?
If you’re facing this challenge, read on! We have developed ten tips for handling slope irrigation, from choosing the right sprinkler to proper controller programming.
#1: Smart controllers with run time limits & multiple start time options
Choose a controller that gives you the option of breaking the watering cycle into parts. The goal is not to exceed the soil’s infiltration rate, which causes run-off and erosion. A controller with a Cycle+Soak option is perfect for the job.
#2: Water outside the lines
Rather than placing your irrigation lines so they run in the direction of the slope, place them across the slope. Be careful to follow the contours of the slope to prevent the pressure differential caused by the changes in elevation from causing uneven pressures throughout the system. Uneven pressures result in poor water distribution and the elevated pressures can damage your system. The knowledgeable staff at Hydro-Scape is happy to offer suggestions!
#3: Master and monitor the flow
Installing a master valve and flow sensing equipment saves a lot of time, money, and hassle caused by damaged systems. The master valve keeps the mainline from pressurizing unless the controller signals an irrigation cycle. Higher-than-normal flows typically happen when a pipe breaks or a sprinkler head fails. The flow sensing equipment catches these errors. You avoid excessive watering and slope damage.
#4: Smaller is better when it comes to irrigation zones
Keeping your zones smaller allows for greater customization of your irrigation system, especially when dealing with slopes. If your hillside has different sun and wind exposures and other climate differences, this customization helps avoid under- or over-watering certain areas. Pressure regulating modules on certain valves also help with this issue.
Smaller zones will allow you to tailor the irrigation system to meet the specific water requirements of the slope areas. Separate zones to apply water to slope sections with different exposures to sun, wind, and other climate influences.
#5: Pressure-regulating nozzles
One way to get rid of misting and fogging is installing pressure-regulating sprinkler heads. Elevation typically causes pressure variances in your system. The resulting higher pressure causes misting and fogging. These special nozzles keep a constant pressure, eliminate water waste, and prevent water loss if a head is damaged or removed.
#6: Matched precipitation rate nozzles or separate zones for part-circle sprinklers
The goal of slope irrigation is to effectively water your plants without eroding the hillside soil. If you’re running part-circle heads and full-circle heads on the same zone, you’re increasing your chances of over-watering. Instead, put the part-circle heads on a different zone and adjust the system run times. An easier option is installing heads that create matching or consistent precipitation rates regardless of radii and arcs.
#7: Compensate for the slope by adjusting the distance between lateral lines
Irrigation plans can be slightly deceiving. A slope’s size can’t really be shown on a two-dimensional map. This means that there’s more to water than it seems. While you can place sprinkler heads consistently along the lateral line of the slope, it’s important to adjust the distance between the laterals themselves. This usually means adjusting those in the middle and those along the bottom to account for the slope.
#8: Install reverse flow zone valves
Sprinkler system valves fail. It’s inevitable. Valves with no reverse flow feature fail in the open position and keep running until you notice them. Reverse flow valves fail in the closed or off position and prevent continuous watering.
#9: Put the mainline at the slope’s base
This one is an easy, but important fix. If your mainline is at the top of the slope and it fails, your slope is going to be flooded and catastrophic erosion will be the result. If you put the mainline at the slope’s base and it fails, your slope is safe.
#10: Every sprinkler should have a check valve at its base
Check valves prevent drainage from the sprinklers after the system completes its cycle. They prevent flooding and erosion by keeping the water in the lateral lines. As a side benefit, check valves also reduce water hammer on system start-up. It’s more convenient to install sprinklers with built-in check valves than it is to install the valves separately.