Natural Resources, School of


First Advisor

Dr. Rezaul Mahmood

Date of this Version



Whitesel, D., 2022: Irrigation’s Impact on a Precipitation Event During GRAINEX in Nebraska, USA, M.S. Thesis, School of Natural Resources, University of Nebraska-Lincoln, 121 pp.


A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of the Requirements For the Degree Master of Science, Major: Natural Resource Sciences, Under the Supervision of Professor Rezaul Mahmood. Lincoln, Nebraska: March 2022

Copyright © 2022 Daniel Whitesel


Numerous precipitation events were observed during the Great Plains Irrigation Experiment (GRAINEX). However, the precipitation event that was observed the morning of 23 July 2018 is the focus of this thesis. Six experiments were conducted which involved increasing or decreasing soil moisture by 5% increments over the irrigated cropland. An additional experiment, which changed the irrigated land use to grassland, showed precipitation increases. It was found that regardless of strength of irrigation, average precipitation decreased. Average precipitation decreased by up to 72% when irrigation increased compared to the control simulation and decreased by up to 85% when irrigation decreased compared to the control simulation. However, when grassland replaced the irrigated agriculture, large increases in average precipitation were reported. When irrigation increased, average latent heat flux increased by up to 28% compared to CTRL and decreased by up to 67% when irrigation decreased. Sensible heat flux decreased by up to 27% when irrigation increased compared to the control simulation and increased by up to 68% when irrigation was removed. The planetary boundary layer over irrigated cropland was found to be shallower and wetter than over non-irrigated cropland. However, the grassland simulation observed a planetary boundary layer that was shallower and wetter than both irrigated and non-irrigated cropland. The changes made to precipitation, the surface energy balance, and the planetary boundary layer served as a reminder of irrigation’s complex effects on precipitation for this event. Analysis on the other precipitation events that were observed during GRAINEX would be helpful to better understand the effects of irrigation on precipitation.

Advisor: Dr. Rezaul Mahmood