Sometimes the issue isn’t a simple, steady lack of rain. Sometimes the rain does come, but during the wrong season or too much all at once, in between long dry periods. When farmers face an unsteady supply of surface water, their first line of defense is usually to access groundwater. Historically, that worked pretty well, but no longer. Now farmers are working to maximize the efficiency of their irrigation systems to make the best use of what’s available, including increasingly expensive or inaccessible groundwater.
In some parts of the Great Plains, annual rainfall has historically been generous, but it often stops midsummer in the peak growing season. Without paying top prices for groundwater delivered to their farms, farmers can face losses of 40% or more in crop yield within a matter of weeks when that happens. Fortunately, there’s a reasonable solution to that problem.
Over the last 15 years, farmers have been increasingly considering ways to even out their water supply by capturing rain and storing it for the next growing season. More importantly, in times when the rains simply don’t come, water stored in irrigation reservoirs could mean the difference between salvaging part of your crop and taking a total loss.
None of this is earth shattering news but taking a big picture approach and designing a purpose-made system is becoming more common. Let’s take a general look at some of the elements you might consider when planning to add, essentially, an irrigation savings account to your farm.
First, consider how much water you need to store, whether for simple seasonal dry spells or for heftier drought insurance. You can plan to fully supply all your fields, or just keep enough on-hand to tide over a few critical acres. If you’re concerned about how a significant drought will affect your feed costs, you may want to consider including irrigated pastureland as well.
Next, examine what you know about your terrain, soil, and your local watershed. Based on your storage needs, identify how many acres of watershed will need to be tapped to keep your reservoir filled from year to year. Depending on your soil type and whether you operate in an area where tiling is common, you may find that you can operate with a smaller watershed. Areas with dense soils that are slow to absorb precipitation and tend to experience high runoff won’t need a big chunk of watershed to meet their needs.
Once you understand where you’ll be collecting runoff, it’s time to consider where you can place one or more reservoirs. To avoid high energy expenditures, it’s ideal to place reservoirs conveniently nearby your irrigation systems so water can be directly pulled from the reservoir and pumped out to your fields. Field edges are good options if your layout allows it, but if that’s prime land, you’ll want to consider that carefully. Keep in mind that there’s real value in storing that water, though. In fact, if you expect to see a 30% increase in yield on average from watering your crops through the peak dry season, you may decide it makes economic sense to sacrifice 5% of your acreage to support that.
Water stored in reservoirs can be used regardless of the irrigation system you use. Pulling water from a surface point will save quite a bit of energy over pulling from a deep well and using a kit to convert your existing point and pivot system to a low energy/pressure system (LEPA or LESA) really brings together the best of both worlds. Similarly, tiled farmland is ideal for subsurface irrigation, where water can be pumped directly from the reservoir through closely spaced drain lines to distribute water to crops. This method reduces evaporative loss and runoff, which makes it about 30% more water efficient than overhead irrigation methods.
