Date of Award:

5-2012

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Civil and Environmental Engineering

Committee Chair(s)

Christopher M. U. Neale

Committee

Christopher M. U. Neale

Committee

David G. Tarboton

Committee

Mac McKee

Committee

Luis A. Bastidas

Committee

Lawrence E. Hipps

Abstract

Evapotranspiration (ET) represents the amount of water consumed by vegetation through transpiration plus the direct evaporation from the soil surface. Understanding the amount of ET is important as it represents a portion of fresh water that is consumed and not available for further use. ET is used as indication of how much water needed for agricultural activities. This research is aimed towards providing improved estimates of ET.

The technological advances in remote sensing provide us with images of the Earth’s surface from space, using satellites, and sometimes with more detail from aircraft. We used these data in models to estimate ET for different land surface cover, including agricultural and natural vegetation. The research objectives were achieved as described in specific technical papers presented in Chapters 2 through 4. Chapter 1 provided a general introduction and Chapter 5 presented a summary and recommendations for future research. In Chapter 2 we introduced new method to estimate daily ET for an entire growing season of rainfed corn and soybean fields of about 10 km by 30 km in Ames, Iowa. This method allowed us to improve our knowledge about how much water is available in the soil in agriculture that depends on natural precipitation.

In Chapters 3 and 4 we studied the ability of using this remote sensing data and other related methods to estimate ET over natural vegetation such as riparian zones that exist within river floodplains. This part of the analysis was carried out over a naturally vegetated area of about 5 km2 at the Cibola National Wildlife Refuge in southern California. This area is covered with invasive vegetation species namely tamarisk (saltcedar) trees that consume considerable amounts of water. We compared estimates of ET which were obtained from using different methods and models.

The research findings provided improved estimates of ET over natural and agricultural area that can be used to better the way we manage our water resources. It also corroborated the usefulness of remote sensing information in this type of application.

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Comments

This work made publicly available electronically on April 10, 2012.

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