Exploring hydroclimatic variability for agriculture and water resource applications on the Delmarva Peninsula
Date
2023
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Publisher
University of Delaware
Abstract
This dissertation examines the influence of hydroclimatic variability on irrigation management, irrigated water usage, and crop yields for the Delmarva Peninsula in a series of three papers. Understanding how these agricultural applications respond to hydroclimatic variability is critical to ensuring the sustainability of agriculture for the region as well as its impact on the regional economy. ☐ The first paper examines the influence of synoptic weather conditions on the relationship between atmometer measured reference evapotranspiration (ET) and Penman-Montieth estimated reference evapotranspiration (ET). As has been shown in atmometer studies in other humid regions, atmometer measured reference ET underestimated Penman-Montieth estimated reference ET. However, this relationship varied between growing seasons. Using a synoptic weather classification index, it was shown that the relationship between reference ET datasets varied depending on the general weather conditions occurring over the region. Correction factors for atmometer measured ET were derived and associated with each synoptic weather category along with general weather descriptions to make the information accessible and applicable to atmometer users in the region, such as the farming community, water resource managers, and other groups interested in the intersection between agriculture and water resources. ☐ The second study modeled irrigated water usage for irrigated farm fields in Delaware using ET-based and calendar-based irrigation scenarios for corn and soybean crop types. Seasonal statewide irrigation totals were primarily driven by the timing of precipitation relative to the peak water demand of crops, while seasonal precipitation played a secondary role. Irrigated water usage data from the two different irrigation management scenarios were compared against high-quality, reported water use data at 259 farm fields from 2014-2018. Agreement was highest for the ET-based irrigation scenario with a fixed amount of irrigation per application for both crop types. Irrigated water use for corn fields displayed slightly better agreement than soybean fields, which tended to be overestimated by the model. ☐ The third paper explored the association between various hydroclimatic drought factors and corn yield for the Delmarva Peninsula. Pentad drought frequencies during the April-October growing season exhibited distinctly different distributions during high and low-yield years, with drought frequencies being considerably higher in the middle of the growing season during low-yield years. This suggests that the frequency of drought factors, such as soil moisture and precipitation minus evapotranspiration (P-ET), have a significant effect on corn yield. Further analysis showed that the time of year when drought factors occur are more important than their seasonal values. Soil moisture drought factors, particularly drought frequency and maximum drought intensity, for July and August demonstrated the greatest influence on corn yield for most counties on the Delmarva Peninsula, while June and July P-ET drought factors also played an important role. Together, these three articles provide practical outcomes for regional agricultural and water resource interests and highlight the importance of monitoring and understanding hydroclimatic variability for the Delmarva Peninsula region.
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Keywords
Atmometer users, Drought factors, Evapotranspiration, Hydroclimatic variability, Water resources