Dr. Rachel Schattman, assistant professor of sustainable agriculture at the University of Maine-Orono, believes both crop and livestock producers might want to have a water management plan. She presented this idea at the 2024 NOFA-VT and MOFGA Climate Forums.
Why Create a Water Management Plan?
“We know that things are going to get warmer. We know that in the Northeast we’re expecting more water overall, but the way that that water comes, either intensity of rainfall or spaced over the season, is going to be highly variable,” Schattman said. “We basically need to be prepared for handling a lot of water all at once, and then potentially stretches like we had in 2020, of very little water for a long period of time.”
According to Schattman, creating a written water management plan is an important tool to assess a farm’s water needs and how it will effectively and efficiently deliver irrigation to crops and/or livestock.
Another reason to complete a plan is that while water availability has not historically been an issue in the Northeast, Schattman believes there is the potential for future increased competition. Water management plans will also be required in the future as farms seek to access funding through state and federal agriculture programs.
What Are Your Water Needs?
The first step is to determine the water needs on the farm. They will depend on the crop being grown.
Environmental conditions such as rainfall and temperature also play a role in determining water needs, as do soil conditions.
According to Schattman, understanding the amount of water being lost from the ground through evaporation and loss of water through the plant itself – a process called evapotranspiration – is key to understanding a farm’s water needs. Irrigation is needed when evapotranspiration is greater than soil water plus precipitation.
“In general, people use evapotranspiration as an irrigation cue out West quite a lot. I think we could use it more here, but it is difficult to calculate,” Schattman said.
To use evapotranspiration as an indicator, a grower needs to know and keep track of soil water content, rainfall in the past week and rainfall forecasts for the coming week. Online calculators exist to help determine evapotranspiration such as Cornell’s Climate Smart Farming Water Deficit Calculator. The user enters soil type, crop type and last irrigation, and it can provide a generalized 30-day outlook for irrigation needs. It’s not specific to a location because it uses precipitation levels from about 700 rain gauges scattered across the Northeast.
If these calculations seem daunting, the rule of thumb for irrigation is at least one inch of water per week (about 27,000 gallons).
“When I say an inch, I mean an acre inch which is the amount of water that it takes to cover an entire acre in one inch of water,” Schattman explained.
In order to think about and calculate long-term water needs, she suggested creating a spreadsheet that estimates water needs by crop based on the 27,000 gallons of water/acre figure. “If you’re irrigating one acre at a time, try to estimate based on everything that you grow in that acre,” she said. Growers should take into account times when plants demand more water, such as corn during tasseling, silking and ear development. Conversely, there are times when growers need to be cautious of overwatering.
Adding ponds to your property can act as insurance that water is available for irrigation in times of drought. Photo courtesy of Rachel Schattman
What Are Your Sources?
This question seems straightforward, but Schattman thinks a comprehensive water management plan should be able to answer some less than straightforward questions for established irrigation sources: What is the capacity of your well? How much water can you draw from a well before it starts to deplete the aquifer? How much water can you legally pull from the nearby stream?
For growers considering adding irrigation sources, surface water including ponds, streams and rivers is most common. Schattman pointed out that a network of ponds can be used to store water pumped from a stream or river. She suggested including an inline water meter in any system to gain an accurate understanding of how much water is moving through the system. Water meters come in a variety of sizes.
Pumping from public surface water comes with the need to be attuned to state laws. For example, Vermont farms require farms that draw more than 10,000 gallons within a 24-hour period anytime in the preceding year (or 150,000 gallons over any 30-day period) to file a report with the Vermont Agency of Agriculture, Food & Markets.
Another option for irrigation is to use groundwater accessed via a drilled well. This may be a more reliable option than surface water; in an informal survey conducted by Schattman, 55% of Northeast farms who used ponds, streams or rivers to irrigate reported that surface water sources ran dry during the region’s 2020 drought.
The U.S. Geological Survey’s National Water Survey provides long-term modeling on wells around the country allowing farms to estimate their local water conditions when making water source development plans. “It can give you a sense of how reliable putting a new system in your area might be,” Schattman said.
She also encouraged growers to consider the novel shallow well to help meet their irrigation needs. More information about these wells can be found at tinyurl.com/2xrfheee.
What Irrigation Method Should You Use?
When designing a new irrigation system, consider total area, water and fuel efficiency, labor and capital availability, topography and water source location. Dealers of irrigation equipment can often help with the design for a new system.
Center pivot irrigation is one option for large acreages. Big gun sprinklers – one gun typically covers one acre – are another option, but do require significant labor when it’s time to move the gun and its pipes. If the topography is flat, hose reels are a possibility.
Currently, there is significant financial funding available from NRCS for improving the efficiency of irrigation systems. “The amount of money that is coming through the Infrastructure Investment and Jobs Act for agriculture is a once in a lifetime opportunity. Making irrigation systems more efficient is one of the ways to reduce fuel use and therefore agriculture’s contribution to climate change,” Schattman said.
Additionally, in specific states, funds for new irrigation projects may be available from Agricultural Management Assistance. Learn more at nrcs.usda.gov/programs-initiatives/ama-agricultural-management-assistance.
by Sonja Heyck-Merlin
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