In August we discussed how to design a garden irrigation plan (https://mothernaturesmontrosegarden.blogspot.com/2020/08/creating-your-colorado-friendly-garden.html). In our example, we modified an existing irrigation system to make it more water-wise. Our example was typical of a smaller, in-town or suburban garden. It showed how irrigation systems can be used in conjunction with Water Zone gardening to create a more interesting and efficient garden. But perhaps you’re faced with a larger, pre-existing irrigation challenge – more like our irrigation system challenge in Mother Nature’s Montrose Garden.
As a first step, we studied the existing wet and dry patterns in the garden (above). We were surprised at the variability in soil moisture. Several dry areas were due to sandier soil that drained very quickly compared to the clay-loam in the rest of the garden. Still other dry areas were due to poor coverage by the existing irrigation system (even after multiple attempts improve coverage). Several wetter areas were due to the slope of the property (lower to the east) or to shade patterns.
The soil moisture patterns suggested options for creating a more water-efficient garden. They also hinted at interesting possibilities hidden in the garden’s existing conditions. The naturally well-drained areas could be planted with native species requiring very well-drained soils. That was good news, as several are among our favorites! Conversely, the moister areas could be used for plants that need a little extra water.
We considered these patterns when designing a Water Zone Plan for the garden, below. Our overall goal was to decrease water use overall, while retaining flexibility for the future. For more on Water Zone Gardening see: https://mothernaturesmontrosegarden.blogspot.com/2020/07/creating-your-colorado-friendly-garden.html
As seen in our Water Zone Map, we plan to retain the front yard lawn – at least for the present. That area will require regular water. So will an apron of lawn around the house in the backyard. But we are in the process of implementing our new garden design; one that will be more interesting and water-wise than the pre-existing landscape (almost all turf lawn). The real question is whether we can adapt the current irrigation system, designed to water lawns, to meet the requirements of our Water Zone Plan!
|Station/Zone 1 [blue]; Station 2 [green]; Station 3 [gold]; Station 4 [orange.|
Stars indicate approximate position of sprinkler heads
The photo above (not to scale) shows the current irrigation system, as designed and modified over the years. The plan’s a bit confusing, but stay with us. The existing system, which irrigates the 1 acre property, consists of 6 stations/zones: Station/Zone 1 (around the house + western front yard); Station 2 (eastern front yard + part of eastern backyard); Station 3 (western backyard); Station 4 (rest of eastern backyard); Station 5 (fills the pond); Station 6 (shade structure located next to shed in NE corner of backyard). The system consists of a number of pop-up, oscillating (Rainbird-type) sprinkler heads, typical for larger yards in Western Colorado.
The existing system seems to have been modified as the landscaping progressed. So, some aspects of the system are perplexing. But there are several fortunate aspects to the design. First, the front yard and the area around the house are all on two Stations (1 and 2). Since we plan to keep these areas in turf grass, they will require more water than other parts of the yard. It’s fortunate that they can all be watered with two irrigation Stations/zones (1 and 2).
But a quick look at the Water Zone Map (above), as well as personal experience, suggests that a few modifications are needed, even to these Irrigation Stations. For example, several sprinkler heads in Stations 1 and 2 irrigate the backyard, just inside the southeast fence. These areas require deep, weekly watering (Water Zone 3) rather than regular water. If unmodified, they will get more water than they need for optimal health.
A quick glance at the Water Zone Map suggests that Stations 3 and 4 will also need to be modified to accommodate different water needs. The large shrubs inside the backyard fence are Water Zone 1-2 (monthly deep water). This watering schedule will be difficult to accomplish with the existing sprinkler heads. In addition, we need to plan for the future: 1) many of the natives will require less water as they become established; 2) climatic cycles of precipitation and drought may change in the future.
All of the above suggest the need to plan for more flexibility in the system. One easy way is to convert some of the sprinkler heads to irrigation risers with spigots (hose bibs). These will allow us to connect hoses, sprinklers and soaker hoses for spot-watering, as needed. Many of the sprinkler heads around the edges of the garden are perfectly suited for this type of conversion. A modified Irrigation Plan, with the risers/hose bib shown as triangles, is shown below.
|Stars indicate sprinkler heads; triangles indicate risers with hose bibs (spigots)|
The final issue is to develop an irrigation scheme for the proposed raised-bed vegetable garden. Fortunately, it will be easy to modify Irrigation Station/Zone 6 to accomplish this. We’ll discuss the details next month, when we consider other aspects of hardscape. In the meantime, we can take a well-deserved break and admire our final Irrigation Plan (below).
|Station/Zone 6 [purple] will irrigate planned vegetable garden|
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