The need for quality irrigation water is increasingly squeezed by competing needs from cities and industry as well as scarcity arising from drought, and aquifer depletion. It’s imperative that farmers devote attention and efforts toward water conservation so that sufficient amounts are available to maintain production. Conservation efforts should include capturing and storing excess water from irrigation and from precipitation events, using efficient irrigation systems, and following up-to-date best management practices. Resilience to periods of water scarcity is critical to maintain a profitable operation and continue to feed the nation’s population.
The choice of crop can also minimize pressure on available water supplies. Since different crops have different water footprints, the choice farmers make of which crop to grow has a huge effect on the region’s water supplies. In California, farmers were widely excoriated for their rapid transition to almond production, a highly lucrative but water intensive crop. While farmers argued that almond trees’ water requirements drop off after the first few years once they’re established, the public questioned farmers’ priorities and they continued to plant new groves during the height of the historic drought that ran from 2011 to 2017. There’s no choice now but to take a hard look at whether crops are suitable for changing climatic conditions in the regions where they’re grown. A serious analysis should be followed by a willingness to make rational, strategic changes. The concept of adjusting crops to climate isn’t new. Over the past 50 years or so in the US, there’s been a gradual national transition in livestock feed from thirsty alfalfa to corn and soybeans, easing pressure on water supplies in those regions. Interestingly, the leading US producer of alfalfa hay is water-strapped California and other similarly arid regions across the western US.
In the end, irrigated agriculture isn’t going to go away - the fact is that irrigated crops are more productive. The same amount of food can be produced on a smaller plot of land, with less labor and less resource use. It makes no sense to abandon that advantage as global demand for food continues to increase. Instead, the focus needs to be on intelligent water management.
Preventing “Too Little Too Late”
It’s impossible to predict whether enough water will be available for any given season unless you start at minimum, with an understanding of how much water you’ll need. With this information plus an educated guess about how much rain will occur naturally during the growing season, you can calculate what you’ll need to replace, and even make allowances for a safety margin to cover unexpected dry spells.
Some crops are particularly water-intensive, while others can at least tolerate dry spells. Early crops and late crops require more water at different stages in their growth, and some crops need dry weather during harvest, for example. Farmers who produce more than a single type of crop on their farms undoubtedly develop cropping patterns to coordinate planting, application of weed or pest killers, and harvest times across the farm. This type of plan can help significantly in determining water needs, especially since you’ll be looking at how much will need to be drawn from your sources at specific times during the year. If all your crops need maximum water applied during the same week, your withdrawals may exceed what you have available at that time. A carefully detailed crop plan allows you to calculate total irrigation withdrawals for any span of time, allowing you to identify problems and adjust.
Smoothing Out Demand
If there are identifiable stretches where daily water requirements exceed anticipated supply, there are some strategies you can use to adjust.
- Adjust your overall planting season to align better with the water supply. For example, if your shortages occur mostly at the beginning of the season, consider delaying planting by a couple of weeks.
- A more nuanced response is to stagger growing seasons by crop or even within crops if you devote a lot of acreage to that crop. Perhaps plant ⅓ at the normal time, then ⅓ a week later, then again, another week later. This may spread periodic demand out enough that your supply (and irrigation equipment) can keep up.
- Expand your storage capability. The more stormwater and captured tailwater you can store, the more flexibility you’ll have to address periods of excess demand.
- Consider switching to a crop with lower irrigation requirements. This isn’t an ideal solution, but it could be the most practical option during extended dry periods.
- Cut down on the irrigated area. If you can produce 75 acres of top-quality corn vs 100 acres of water stressed, it’s likely to be a good exchange.
- If none of these options are possible, then the final solution may be simply to accept the anticipated water shortages and resulting production losses. It’s not ideal, but you can take some time this year to make a better plan for the next.
Waste Not, Want Not
It can feel like quite a struggle to collect even relatively small amounts of water when you’re trying to irrigate potentially hundreds of acres, so it’s especially discouraging when you realize how much you may be wasting in daily operations. That’s water you’ve paid for, whether in cash or in labor. Take some time to consider where water losses may appear and what actions are possible to minimize or eliminate them. Any wastage you can eliminate is, essentially, an extra contribution to your supply.
Surface water, like lakes and reservoirs, lose water through seepage from the bottom and evaporation from the surface. These losses can add up quickly. In hot, arid climates, evaporative losses from open water can approach 2 inches per day. On a lake with 10 acres of surface area, that’s over 500,000 gallons.
The key with evaporation is that it can only happen from the surface of the water. Shallow but expansive bodies of water will lose far more than deep reservoirs with a small surface area. You can mitigate this problem when you design your reservoir. Planning for depth rather than width also helps you minimize the amount of potential cropland you end up sacrificing. You can aim for an average depth between 7 and 12 feet to minimize surface area; just be sure that your excavation is sloped and structured to handle water motion and repeated fills/empties.
Another strategy to deal with evaporation is to prioritize withdrawals from sources most vulnerable to that kind of loss. If you have several surface reservoirs plus an allotment of withdrawals from a community source like a river, consider drawing from your shallowest reservoirs early in the season, before they’ve had an opportunity to lose too much stored water.
Irrigation on a modern farm is much more complex than carrying a few buckets of water to your garden every few days. In fact, irrigation produces its own inherent opportunities to waste water. As farmers examine their farming activities and prepare to capture and store water in irrigation reservoirs, it’s important to take a good look at the irrigation system itself.
