MASARYK UNIVERSITY Faculty of Science Department of Geography Roman BOHOVIC MODELLING EVAPOTRANSPIRATION AT DIFFERENT SCALES BY THE MEANS OF REMOTE SENSING Diploma thesis Supervisor: doc. RNDr. Petr Dobrovolný, CSc. _________________________________________________________________________ Brno 2009 Author: Roman Bohovic Title of the thesis: Modeling Evapotranspiration at Different Scales by the Means of Remote Sensing Title in Slovak: Modelovanie evapotranspirácie v rôznych merítkach postupmi diaľkového prieskumu Zeme Programme of studies : Geographical Cartography and Geoinformatics Supervisor: doc. RNDr. Petr Dobrovolný, CSc. Year: 2009 Annotation Khorezm province (Uzbekistan) lies in Amu Darya delta and is afflicted with the problems caused by the Aral Sea desiccation. Agriculture is the major source of livelihood, but it is fully dependent on the irrigation. Therefore, sustainable water management and sensible use of the water are crucial. The main aim of this study was to provide high-resolution evapotranspiration (ET) data. This was achieved by the modelling of remotely sensed ASTER images. For that, Surface Energy Balance Algorithm for Land (SEBAL) with METRIC modification was applied. The modelling process proved suitability of the data and the method for this purpose. As an output of this study, dataset (7 scenes) of the actual ET for the years 2004 – 2007 was created. In addition, maps of the ET and basic analyses were done upon modelled data at the second part of diploma thesis. Anotácia Chorazimská oblasť (Uzbekistan) sa nachádza v delte rieky Amudarja a je postihnutá problémami spôsobenými vysychaním Aralského mora. Poľnohospodárstvo je hlavným zdrojom obživy v regióne. Keďže je úplne závislé na zavlažovaní, citlivé zaobchádzanie a trvalo udržateľné hospodárenie s vodou sú veľmi dôležité. Hlavným cieľom tejto štúdie bolo vytvoriť podrobné dáta o evapotranspirácii (ET). To bolo dosiahnuté modelovaním družicových snímkov zo snímača ASTER s použitím metódy SEBAL (Surface Energy Balance Algorithm for Land) s modifikáciou METRIC. Zvolený postup aj vstupné dáta sa ukázali pre účel tejto diplomovej práce ako vhodné. Výsledkom je 7 dátových vrstiev aktuálnej ET v období rokov 2004 – 2007. V závere práce boli na základe vytvorených dát urobené jednoduché analýzy a dáta boli kartograficky vizualizované do výslednej mapy evapotranspirácie. Keywords: evapotranspiration ○ SEBAL model ○ ASTER ○ Uzbekistan remote sensing ○ raster data modelling ○ GIS analyses Kľúčové slová: evapotranspirácia ○ model SEBAL ○ ASTER ○ Uzbekistan diaľkový prieskum Zeme ○ modelovanie rastrových dát ○ GIS analýza THANKS TO Dr. Christopher Conrad ○ doc. RNDr. Petr Dobrovolný, Csc. ○ Dr. John Lamers Lucia Šikulincová Avo Tuahrem ○ Berousek ○ Gunter ○ Dano ○ Zuza ○ Lenka ○ Osman ○ Mardon 19 years of education rodičom I KNOW WHAT FOR I claim, that I elaborated this diploma thesis under the supervision of my supervisor (doc. Dobrovolný) and consultant (Dr. Conrad) and with some kind of help from the people mentioned above. May 15th, 2009 Brno ____________________________ signature TABLE OF CONTENTS PREFACE.............................................................................................................................7 1 GENERAL INTRODUCTION...........................................................................................9 1.1 Aim of the study..........................................................................................................9 1.2 The study region: Khorezm Oblast..............................................................................9 1.2.1 Physical geography of the study area.................................................................11 1.2.2 Socio-economical conditions.............................................................................14 1.2.3 Land cover and agriculture................................................................................15 1.3 Irrigation and drainage system..................................................................................18 1.4 Evapotranspiration.....................................................................................................20 2 MODELLING EVAPOTRANSPIRATION.....................................................................22 2.1 Input data...................................................................................................................22 2.1.1 ASTER data.......................................................................................................22 2.1.2 Meteorological data...........................................................................................26 2.1.3 Land cover and land use data.............................................................................27 2.2 SEBAL and METRIC models...................................................................................28 2.2.1 Physical principals of SEBAL...........................................................................28 2.3 Modelling ET ............................................................................................................30 2.3.1 The 1st phase of the model................................................................................31 2.3.2 The 2nd phase of the model...............................................................................33 2.3.3 The 3rd phase of the model................................................................................36 2.3.4 The 4th phase of the model................................................................................40 2.4 ASTER – MODIS result comparison........................................................................42 2.5 Results and discussion...............................................................................................45 3 GEOPROCESSING ANALYSES...................................................................................48 3.1 Patterns of ET distribution.........................................................................................48 3.2 Relative differences in the actual ET.........................................................................51 3.3 Discussion..................................................................................................................52 CONCLUSION...................................................................................................................54 REFERENCES....................................................................................................................56 APPENDICES.....................................................................................................................59 ABBREVIATIONS.............................................................................................................62 6 PREFACE Uzbekistan is not a particularly popular tourist destination. Its location, strict visa policy and complicated administrative regulations for residence make the visit considerably difficult, especially for Europeans. Rather by chance, I got involved the Erasmus Mundus External Cooperation Window Lot 9 programme. The aim of this project is to bring European and Central Asian universities together, by way of a mobility scheme accepted by the European Commission (EMEC9, 2009). In February 2008 I arrived to Urgench in Khorezm for one term as an exchange student on the Urgench State University Named after Al-Khorazmy (Al-Xorazmiy Nomli Urganch Davlat Universiteti), see it on the Figure 1. Figure 1: Entrance to the Urgench State University Named after Al-Khorazmy. Khorezm province, with Urgench as a capital, is one of the remotest parts of Uzbekistan, landlocked in the Central Asia deserts. Neither Uzbeks nor the foreigners commonly visit this area (except for the Khiva UNESCO world heritage site). In spite of its famous history (it has a reputation once being a centre of intelligence and education) it is very isolated region nowadays. The fame of the Khorezm oasis on the Silk Road has faded since the medieval times. The Khiva Khanate used to be on the crossroads, where not only trade, but also culture and ideas from the east and the west used to mingle. The present situation in the country is rather difficult and complicated. Poor economical and social conditions are now accented by the global economic crisis. According to the International Crisis Group reports (2009), an authoritarian regime in the country is very severe particularly in this region, moreover accompanied by serious 7 violation of human rights. The human development index of Uzbekistan is 0.702 (in 2005), which is at the 113th place in the world (ADB, 2009). Local conditions in the Khorezm oblast seem to be even worse, due to its social and spatial isolation from the other populated regions. Besides social problems, Khorezm is afflicted with environmental difficulties as well. It lies in the Aral Sea basin. The lake used to have a moderate effect on the local climate, attenuating extreme frosts during the winter and high temperatures in summer. Because of the ecological disaster in Aral Sea, this positive effect on the local conditions is disappearing. This leads to the lake desiccation, and consequently gives rise to other problems as well (sand storms, salinization, soil degradation, diseases, etc.). The major problem affecting this area is the water shortage and droughts. As the agriculture is the major source of livelihood, being fully dependent on the irrigation, sustainable water management and sensible use of the river water are crucial for this