Access to water for irrigation is increasingly under pressure across the country, but is investing in an irrigation reservoir a reasonable solution?
A Question of Resiliency
Changing climate patterns, urbanization, population growth, drought and excessive heat, saltwater intrusion and aquifer depletion, even changes in policies are creating a perfect storm that leaves farmers with too little water available for their crops. In these circumstances, if farms are to survive, farmers have no choice but to develop new strategies for water management. Resiliency, in this instance, refers to the ability of a farming business to withstand the risk and crop injury associated with water scarcity and extended drought, exacerbated by a changing climate. It’s a tall order. Beyond maximizing efficiency, resiliency will require farmers to explore sources for supplemental and backup irrigation water. Without those strategies in place, a farming operation may face bankruptcy after a single season.
Strategic water management includes husbanding the resources that are available by establishing effective storage, lossless transportation, efficient distribution to the crops, and careful collection of overflow from both irrigation runoff and precipitation events. Use of irrigation return water also requires an investment in systems designed to treat it and remove impurities that could harm crops.
Irrigation reservoirs are used to store water for regular irrigation or to collect water during off-season for later use. Reservoirs can support supplemental irrigation and separate reservoirs can collect and provide retention time for irrigation runoff, or tailwater.
Crop Support
Supplemental irrigation using water collected in a reservoir can be extremely valuable in boosting crop yields and making yields more stable. When allotments from nearby surface or groundwater sources are reduced or even cut off altogether, rainfall during the growing season may not be adequate or quite regular enough to keep your crops at their peak. Even in the fairly wet Eastern states, farmers have found that eliminating crop water stress even during short dry spells can boost corn yields 30% or more. Overall resiliency planning demands that farmers work on minimizing their total water usage, no matter the source, but capturing and reusing tailwater actually protects the environment.
Recycling
Drainage, or tailwater, can be a valuable source of supplemental water for farmers. Field runoff may contain fertilizers, nitrates, and valuable sediments which can be returned to the fields, reducing the need for additional fertilizers and chemical supplements. Fertilizers, in fact, are severely damaging to surface water systems, where they degrade fish habitats, feed algae, and can trigger dangerous blooms.
Captured tailwater may be directed first to a settling pond, where larger particles can sink to the bottom before it’s released into the storage reservoir. This step helps prevent fouling of pumping equipment and excessive buildup which will eventually reduce the storage capacity of the reservoir. Settling ponds, in contrast, are smaller and shallower and much easier to clean out.
Some tailwater collection systems are connected to constructed wetlands which provide essential water treatment without the need to invest in equipment which must be powered, maintained, repaired, and eventually replaced. Wetlands are nature’s natural filters and can absorb, break down, sequester or remove an impressive range of contaminants ranging from fertilizers and agricultural chemicals to toxic heavy metals.
Protecting the Environment
The agricultural industry needs to focus on good environmental stewardship as more than a ‘feel-good’ activity. Irrigation runoff, carrying phosphates, nitrates and agricultural chemicals present a significant threat to surface water and even groundwater systems, which happen to be not only the source of most of your irrigation supply but also your local drinking water. Contaminated runoff degrades overall water quality in downstream streams, rivers, lakes and reservoirs, which then may render it unusable for either municipal or farm use. When water supplies are already limited, allowing those supplies to be contaminated with deadly toxins such as cyanobacteria, or blue-green algae represents a harsh 1-2 punch.
Ultimately, the purpose of an irrigation reservoir is to capture water that would normally flow past your crops and empty into surface waters, possibly carrying harmful contaminants that can damage the local ecosystem. Whatever is captured can be stored and used to irrigate your crops, either as a primary or supplemental source.
