Excluding water used for environmental purposes, agricultural uses during “normal” (historical average) hydrology years account for about 45% of all water used within the State.[1] In Tulare County, Agriculture accounted for 95% of net water use during WY2015 (very dry) and 86% during WY2002 (close to “normal”, historical average). The very high percentage of agricultural use in Tulare County is attributable to low urban water use due to low population density, and relatively few environmental flows[2] (10% in WY2002 and 2.4% in WY2015).
During calendar year 2015, agriculture accounted for 42.6% of non-residential electric energy (kWh) and 49.3% of non-residential electric demand (kW).[3]
The magnitude of both water and electric resource requirements makes agriculture a very high priority for technology investment in Tulare County, since even modest efficiency gains can yield tremendous resource benefits. Considerable environmental and economic benefits associated with saving water and electricity are also achievable.
A 5% reduction in agricultural water use could have saved 136 TAF during WY2002, more than the total annual urban water demand of 133 TAF.
During very dry WY2015, a 5% reduction in agricultural water use could have saved 139 TAF - 74% more water than was needed to meet countywide urban demand of 80 TAF that year,[4] and still more than total urban water use during WY2002, a “normal” water year.
Examples of Water-Efficient Technologies
Some technologies focus on continually improving the efficiency of water delivery to crops through enhanced research and understanding about various crops’ responses to different irrigation methods.
Some technologies focus on enhancing real-time water management by merging telemetry with drones and decision-making software to create tools that enable farmers to make water use decisions from their phones.
Others are bringing both biological and physical solutions that increase the efficiency of water uptake by crops to increase crop yields per unit of water applied.
California is not alone - global water supply and quality pressures have spurred worldwide research in agricultural water use efficiency. The scope of explorations has spanned studies aimed at understanding the differences among various crops as to the quantity, quality and timing of water needed to optimize yields, and improved irrigation technologies that increase precision of applied water. Meanwhile, California’s unpredictable hydrological cycles and events, policy goals, increasingly stringent regulations, and public health concerns (e.g., with water quality) have created sophisticated farmers, equally knowledgeable about both business and science, that continually assess and reassess the crops that they plant and the efficacy of strategies and technologies for reducing regulatory, resource, environmental, and economic risks.
Stakeholders' Recommendations
These types of technology solutions have significant value for Tulare, the largest agricultural producing county in California. However, through meetings with a wide variety of agricultural stakeholders (farmers and technical services providers), one technology need emerged as a very high priority for Tulare, and that is the ability to use manure effluent via drip irrigation.
Dairy farming and milk production is the largest agricultural activity in Tulare County, using about 52.8 TAF per year (17 billion gallons) and 38.2 % of annual agricultural electricity (kWh). One of the biggest challenges that dairy farmers face is efficient reuse of manure effluent.
Conventional manure sludge dewatering processes leave solids that are too large for drip nozzles, causing lines to clog. For this reason, alfalfa and other fodder crops are flood irrigated with the manure effluent.
Flood irrigation is vastly inefficient compared to other irrigation methods. One dairy farmer estimated that enabling use of manure effluent for drip would reduce applied water by 20% while concurrently increasing yield by 33%, a net water efficiency gain of 41%. This estimate is consistent with a research project conducted by Sustainable Conservation, De Jager Farms in Madera County, and Netafirm USA that delivers liquid manure to fodder crop roots via subsurface drip irrigation (SDI):
“A 2015 pilot of the system on a 40-acre (16.2-hectare) field of silage corn at De Jager Farms produced stellar results. Water use efficiency increased by 38 percent, nitrogen use efficiency by 52 percent, and corn yield by 15 percent.”[5]
[1] DWR’s Water Portfolio Tool estimated total water use in California during very dry water year 2015 at 64,129 million acre-feet (MAF), with urban water use accounting for 10.9%, agricultural 50.5%, and environment 38.6%. During an average water year (2002), the relationships were 11.4% urban, 45% agricultural, and 43.6% environmental. Source: “Water Supply & Balance Data Interface, ‘Lite’ ver. 9.1.” Downloadable from California Department of Water Resources’ website: https://water.ca.gov/Programs/California-Water-Plan/Water-Portfolios.
[2] Environmental flows are water uses that sustain natural waterways and ecosystems. Environmental flows may occur naturally – e.g., due to precipitation and runoff. They may also be stipulated by laws or regulation when needed to sustain fresh water systems for species, and ecosystems, especially when natural water flows have been diverted or may be impeded by manmade dams, surface water storage systems, and other types of manmade barriers that divert or interrupt natural water flows.
[3] Source: Southern California Edison. See Appendix M: Tulare County’s Water-Energy Nexus, Table 30. Largest Electric Consumers by NAICS Code (Calendar Year 2015).
[4] Urban demand during water year 2015 was low due to a combination of water supply shortages and mandatory water use reductions.