Energy & Cost Impacts: Irrigation Decision Support Systems

California’s stable, predictable, Mediterranean climate and quality soils contribute to its acclaim as one of the most productive agricultural regions in the world, with over $20 billion in annual revenue added to the Californian economy. This success is underpinned by irrigation. Each year, approximately 42 km 3 of water is used to irrigate some 12 million hectares to grow over 350 different individual crops. This water accounts for approximately 80% of all developed water (i.e. water that is controlled and managed for a variety of purposes) used in the state.

Surface water is not sufficient to meet this demand, and California relies on water stored in its 515 groundwater aquifers to provide 40-60% of the statewide irrigation water supply. Indeed, the transport of water through the vast network of water conveyances throughout the state, and pumping of surface- and groundwater for irrigation, account for a large portion of California’s annual energy demand. Even small improvements in water use efficiency can therefore be significant.

Although the use of water by Californian farmers is already relatively efficient, better tools that can provide accurate assessment of crop water needs, such as those represented by the Irrigation Decision Support Systems (IDSS) addressed here, could provide significantly higher savings. Estimates of water savings under ideal conditions for large-volume crops such as tomatoes reach up to 29% 1 . With a standard pump efficiency of 60%, a minimal friction loss of 5 m and at typical flow rates, such water savings could translate to savings of up to 25, 105 or 450 kWh/ha/yr for a typical Central Valley tomato field irrigated with surface, shallow groundwater (8 m), or deep groundwater (50 m) respectively. Detailed estimates of water and energy savings are provided in Performance Evaluation Results.

At the same time, the energy outlay for a standard IDSS system is minimal. Typically, the sensors and data logger components of IDSS systems are powered by small solar panels in the field. However, technologies that rely on aircraft to provide snapshot views of fields are a relatively small but important category where fuel costs and higher operating costs need to be considered. At the same time, as significant portion of the costs is associated with flight time to and from the surveyed fields, costs and relative energy use decrease rapidly with farm size. Cooperative systems where multiple farmers in one location would purchase aircraft-borne instrument services are also likely to be mutually beneficial and bring the costs down. These systems also do not provide data with of sufficient frequency for daily irrigation scheduling. Rather, irrigation and energy savings are realized through identifying problem areas and optimizing irrigation and fertilizer application across entire farm fields and could work best as complementary systems to in-field IDSS sensors that provide real-time analysis of field conditions for irrigation scheduling.

References
(1) Ebert, L. A.; Gal, A.; Brooks, W.; Turini, T.; Jha, G.; Lazcano, C.; Gaudin, A. C. M.; Scow, K.; Nocco, M. A. Tapered Deficit Irrigation Strategies Can Reduce Water Use in Processing Tomatoes. California Agriculture 2025, 79 (2). https://doi.org/10.3733/001c.138274.