Water Resources Research Act Program

Details for Project ID 2017NE291B

Impact of Variable Rate Irrigation on Consumptive Use of Water Resources

Institute: Nebraska
Year Established: 2017 Start Date: 2017-03-01 End Date: 2018-02-28
Total Federal Funds: $20,000 Total Non-Federal Funds: $40,002

Principal Investigators: Derek Heeren, Daran Rudnick, Francisco MunozArriola

Abstract: In Nebraska and many other areas in the world, irrigation is the largest single user of water resources. Optimal use of irrigation water is increasingly necessary to meet future water demands and to meet other economic, environmental, social, and political constraints. The premise of variable rate irrigation (VRI) technology is that irrigation requirements may vary spatially within a given field and therefore spatially varying irrigation application would be beneficial for optimal water use. Variable rate irrigation (VRI) may lead to a variety of benefits, which include decreasing pumping energy expenses, lowering the frequency/severity of yield loss and stuck pivots due to over-irrigation, avoiding chemigation over non-cropped areas, reducing irrigation runoff on hillslopes, and decreasing nitrate leaching. A common misunderstanding regarding new irrigation technologies (e.g. conversion from furrow irrigation to sprinkler irrigation) is that they conserve water, with reduced pumping resulting in more water available to downstream users. This misunderstanding is often applied to VRI technology. Stakeholders in Nebraska are rightly concerned about aquifer level declines and the subsequent impacts on streamflow. VRI is reported to reduce pumping for irrigation, but it is often assumed that the reduction in groundwater withdrawals will have a positive impact on groundwater levels and streamflow. This research hypothesizes that, while VRI can be used to reduce pumping or increase yield, it does not significantly reduce consumptive use. The specific objective of this project is to utilize field experiments to quantify the impact of VRI on consumptive use of water resources. In order to develop best management practices, a new center pivot VRI system (individual sprinkler control) was installed on a 120 ac corn-soybean field at the UNL Agricultural and Research Development Center (ARDC) near Mead in southeastern NE. In 2016, the research was expanded to include a second field site at the UNL Brule Water Lab (BWL) in western Nebraska. If funded, this project would provide support for students who would continue the field experiments at the two locations for an additional season (2017). The water balance will be quantified in order to calculate actual ET for each plot location. The consumptive use (i.e. seasonal ET) will be compared for VRI and conventional irrigation. Yield, irrigation applied, and water use efficiency will be compared for the uniform irrigation and the two VRI strategies. Outcomes from this project will include a Nebraska extension publication on quantifying the benefits of VRI (i.e. reduced pumping and possibly reduced consumptive use) and one peer-reviewed journal article.