Date of Graduation

5-2021

Document Type

Thesis

Degree Name

Bachelor of Science in Biological Engineering

Degree Level

Undergraduate

Department

Biological and Agricultural Engineering

Advisor/Mentor

Runkle, Benjamin

Committee Member/Reader

Moreno-Garcia, Beatriz

Committee Member/Second Reader

Reba, Michele

Committee Member/Third Reader

Henry, Christopher

Abstract

Global food production must increase to meet the demand associated with increased population growth, so irrigation water use will continue to rise. Therefore, it is important to monitor water usage particularly when an irrigation flowmeter is unavailable. A field water balance was created for a selection of rice fields in East-central Arkansas under observation in 2018 and 2019. From those, irrigation inputs are deduced from the water balance alone. First, each field had sensors that collected water table level (WTL) data. Next, other water inputs and outputs such as precipitation and evapotranspiration (ET) were collected from two modeled sources. The remaining outputs—levee seepage, deep percolation, and runoff—were assumed to be negligible. The water balance was created for a production-scale field that is zero-grade with no drainage and another production-scale field (0.18% slope) with no drainage. This water balance model was tested against irrigation data that was collected for each field during the growing season either with flowmeters or written records from the farmer. The results indicate that the water balance may have potential to predict irrigation on days when the WTL is positive. The model was not very accurate, but the results were mostly consistent for each field. The model underpredicted irrigation by approximately 50% for both fields, likely due to the drainage factors that were originally considered negligible and inaccuracies of the modeled sources. However, with more research, these factors can be properly assessed and included as necessary to ensure more accuracy. Farmers and scientists will both then be able to use this approach to track water usage and compare different irrigation methods to determine which practice conserves the most water while maintaining yield.

Keywords

irrigation; rice; water balance; Arkansas

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