Preface

Chapter 8 **A Parametric Model for Potential Evapotranspiration**

Zohreh Izadifar and Amin Elshorbagy

Chapter 10 **Influence of Soil Physical Properties and Terrain Relief on**

**Arable Land Determined by Energy Balance and**

Chapter 11 **Uncertainty Evaluation of Water Budget Model Parameters for**

A. Al-Busaidi, T. Yamamoto, S. Tanak and S. Moritani

Chapter 13 **Reference Evapotranspiration (ETo) in North Fluminense, Rio de Janeiro, Brazil: A Review of Methodologies of the Calibration for Different Periods of Analysis 259** José Carlos Mendonça, Barbara dos Santos Esteves and Elias

**Different Environmental Conditions 227**

Chapter 12 **Evapotranspiration of Succulent Plant (Sedum aizoonvar.floibundum) 241**

**Monteith Equation 143**

**VI** Contents

**Bowen Ratio 207** Renata Duffková

Fernandes de Sousa

**Estimation Based on a Simplified Formulation of the Penman-**

Aristoteles Tegos, Andreas Efstratiadis and Demetris Koutsoyiannis

**Actual Evapotranspiration in the Catchment with Prevailing**

Zoubeida Kebaili Bargaoui, Ahmed Houcine and Asma Foughali

Chapter 9 **Data Driven Techniques and Wavelet Analysis for the Modeling and Analysis of Actual Evapotranspiration 167**

> Evapotranspiration has been the subject of thousands of research articles during the last cen‐ tury. It is a complicated subject, involving a number of interrelated procedures and stand‐ ard, engaging a complex set of processes, which themselves are influenced by many factors dependent on local or global spatial scales of natural regimes. Maxwell in 1965 estimated that about ten trillion cubic meters of water per day returned to the atmosphere by evapora‐ tion and transpiration from the surface of the United States.

> Despite the large number of scientific works worldwide on evapotranspiration, the phase transition of water into the biosphere is still an important area of investigation for the Geo‐ sciences. This book is designed to further enhance presenting recent investigations of many scientists on evapotranspiration modeling around the world. Thus, the objective of this book is to provide timely and comprehensive coverage of the principles, modeling and methods of measuring evapotranspiration from a single typical experimental site to large study areas, into natural and rural ecosystems.

> The collective effort that solidified in this book, is only a minor part of the long line of hard research work that devoted scientists have contributed to the investigation of physical reali‐ ty, to the never-ending struggle of man to unravel the unknown through logic and reason. Can this quest end? "…Evaporation is the most desperate branch of the desperate science of Meteorology…", Symons said as early as 1867.

> The first chapters refer to the more general subjects and are followed by chapters with a more specific focus. Each chapter, however, was individually considered within this context.

> The topics describe the latest research on ET estimation. The Bowen Ratio (BR) method, the complementary relation method (CR), the Penman Montieth (PM) method for estimating reference evapotranspiration, other simplified methods such as the Priestley Taylor method, or novel approaches on the simplification of the PM method with more emphasis on the empirical approach are all illustrated in the chapters of the book, in the framework of projects which include basins, rivers, or the laboratory setting of an experiment in a control‐ led environment.

> These methods are a part of, or used in conjunction with models like NICE (National Inte‐ grated Catchment-based Eco-hydrology), WREVAP which is based on the CR method, HYDRUS2 which elaborates on the movement of water in the ground, an arithmetic solution of the Richards equation, as well as models that use satellite data or even models that utilize Artificial Neural Networks (ANN).

> An equally wide range can be seen in the types of input data for the methods and the mod‐ els used.

The research work estimates the quantity of AET, its relation to soil moisture and soil type, vegetation cover, land use, topography, weather conditions, climatic associations and geolo‐ gy. It compares the various methods in terms of their ability to predict, investigates topics like the spatiotemporal patterns of AET, the underlying relation of these patterns with plant development, the succession of the seasons during a year, and the subsequent variation in temperature, moisture, etc. It explores the limitations of the methods used, quantifies alter‐ native management scenarios, and the effects of irrigation treatments with different water quality on AET.

The objective of this book isn't only to provide the knowledge, competencies and skills to serve as a recipe on water conservation, but seeks to contribute to the understanding the role of evapotranspiration and latent heat on the sensitivity of the climate system by bring‐ ing together the work of modelers and others involved in the analysis of observational data.

We are hopeful that the book "Evapotranspiration – An Overview" will provide a wider knowledge and may be a useful tool for many complicated aspects related to hydrological and specific environmental phenomena, as well as will put a premium on accurate approach of the mechanism of the water movement on the earth climatic system.

The editor is grateful to the authors who participated in this book project for their scientific contributions, which consists a useful volume on the topic of the state of the art applications of remote sensing and ground-based methods for ET estimates.

Lastly, I express here my sincerest thanks to the co-editor Prof. Ruzica Stricevic and our partner, Dr. Costas Chatzithomas for the manifold suggestions which I have received from them, and for their constant input of this work.

#### **Editor, Stavros Alexandris**

**Chapter 1**

**Water Balance Estimates of Evapotranspiration Rates in**

In the continental United States, approximately 2/3 of all rainfall delivered is lost to evapo‐ transpiration (ET; US Water Resource Council, 1978). It follows that the ET rate, representing the combined processes of physical evaporation and biological transpiration, is essential for predicting water yields, designing irrigation and supply projects, managing water quality, quantity, and associated environmental concerns, and negotiating disputes, contracts, or treaties involving water. Water fluxes in catchments are controlled by these physical and biological processes as well as by hydrogeologic properties that are complex, heterogeneous, and poorly characterized by field and laboratory measurements. As a result, practical theories of ET rates and their impact on runoff generation and catchment hydrology remain elusive. Many methods have been used to determine ET rates in watersheds. Since atmospheric vapor flux is difficult to measure directly, most methods monitor the change of water in the system. Potential ET (PET), the amount of ET that would occur if unlimited water were available, can be measured using an evaporation pan or ET gauge. Pan data can also be used to estimate the actual ET, representing the ET that occurs when water is limited, for the vegetation of interest using relationships presented by Jensen et al. (1990). Lysimeters, soil water depletion, and the energy balance method have also been used to estimate ET (e.g., van Bavel, 1961), though measurements are difficult. Another approach, the water balance method, provides simple, effective estimates of ET rates if accurate stream gauging and precipitation data are available. This method is generally used for large watersheds, and compares water inputs (e.g., precip‐

itation) and outflows (e.g., stream flow) for a given basin over long periods of time.

This paper uses the water balance approach to calculate ET rates by comparing precipitation and runoff data for watersheds. We expand on this traditional method to show how ET can be deconvolved into physical and biological components whose magnitudes vary both

> © 2013 Hasenmueller and Criss; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2013 Hasenmueller and Criss; licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,

distribution, and reproduction in any medium, provided the original work is properly cited.

**Areas with Varying Land Use**

Elizabeth A. Hasenmueller and Robert E. Criss

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/52811

**1. Introduction**

Department of Natural Resources Management & Agricultural Engineering, Sector of Water resources Management Agricultural University of Athens, Greece

> **Co-editor, Prof. Ruzica Stricevic** Faculty of Agriculture, University of Belgrade, Serbia
