DAOU Ibrahima, MARIKO Adama, RASMUS Fensholt, MENENTI Massimo, KOUROSH Khoshelham, MBOW Cheickh, DIALLO Drissa / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue 5, September- October 2012, pp.1193-1200 Estimation and cartography of the evapotranspiration from the data AATSR in Sudano–sahelian environment: case study of Kolondièba-Tiendaga basin (Mali) DAOU Ibrahima.1 MARIKO Adama.2 RASMUS Fensholt.3, MENENTI Massimo.4, KOUROSH Khoshelham.4, MBOW Cheickh.5, DIALLO Drissa.1 1. University of Bamako, Faculty of Science and Techniques (FAST), Mali 2. National Engineering school-Aberhamane Baba Touré of Bamako, Mali 3. University of Geography and Geology of Copenhague, Denmark 4. Delft University of Technology, Department and flesh, Remote Sensing optical and laser Remote sensing, Netherlands. 5. University of Cheick Anta Diop (UCAD), Laboratory of Education and Research in Geomatics Abstract Information on the space and temporal variation of the evapotranspiration on a basin I Introduction area is of capital importance in many The estimation by remote sensing of the environmental disciplines, such as hydrology, corresponding evapotranspiration (to the latent agriculture, integrated management of the water flux of heat) is based on the evaluation of the resources, meteorology, etc. Moreover, this energy balance of surface through several information plays a crucial part in the processes properties of surface, such as the albedo of surface, of interaction between the hydrosphere- the temperature of surface, the vegetation index Biosphere-Atmosphere, and water cycle. The (LAI, FCover, NDVI) and meteorological data[7]. evapotranspiration can be measured through The measure continues and the spatial variation of two approaches (conventional or traditional and the evapotranspiration, at various scales (ladders) remote sensing approaches). The conventional are important parameters in the evaluation of approaches make it possible to have very precise agriculture water requirement [24]. This results but confined on reduced spaces. While evapotranspiration represents a key parameter in the approaches of remote sensing lead to such several environmental disciplines, such as, satisfactory results likely to be extended to hydrology, agriculture (farming), integrated broader zones. management (joined) by water resources, [24], [25] The satellite images are more and more used to and play a dominating role in the process of estimate and map the space and temporal interaction between hydrosphere-Biosphere- distribution of the evapotranspiration starting Atmosphere and water cycle. It depends on the from patterns such as SEBS (Surface Energy availability of water, and the incidental solar Balance System). This article has the results of radiation and reflects essentially the interaction the estimate of the evapotranspiration starting between water resources and climate. The reliable from model SEBS (Surface Energy Balance estimation of the evapotranspiration allows System) on the basin area of Kolondièba- improve the performance of the systems of Tiendaga (3050 km2) in sudan-sahelian climate, irrigation.[24], [25], and can be made through two in Southern Mali. The results of this study show approaches (the conventional or classical a strong correlation between the approaches and the surrounding areas of remote evapotranspiration and the evaporative fraction sensing). from 2003 up to 2008, where the coefficients of The conventional approaches supply precise correlation vary between 0.60 and 0.90. On the measures through homogeneous zones, on small other hand, this coefficient becomes lower than scales, and cannot be spread to hypermarkets, 0.50 for the two last years 2009 and 2010 (0.34 because of the regional variation of the climatic and 0.40). The values of the evapotranspiration parameters, the heterogeneousness of the landscape vary between 1 and 3mm/J -1 and the dynamic nature of heat transfer processes. [33]. Keywords: Evapotranspiration, SEBS, Among these conventional methods, the method evaporative fraction, Basin of Kolondièba- of Penman-Monteih is both mostly known and Tiendaga, AATSR images used. This classical method combines (at the same time) energy and the balance sheet of mass transfer 1193 | P a g e DAOU Ibrahima, MARIKO Adama, RASMUS Fensholt, MENENTI Massimo, KOUROSH Khoshelham, MBOW Cheickh, DIALLO Drissa / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue 5, September- October 2012, pp.1193-1200 to model the evapotranspiration. It was proposed by between 900 and 1200mm / year. The monthly Monteih in 1965 which leaned on the equation of average temperatures vary between 38 ° in May Penman in 1948 [6]. and 23 ° in December. The values of the relative Surrounding areas of remote sensing are based humidity oscillate between 82 % in August and 38 on the evaluation of the energy balance of surface % in February. The radiation is strong all year long, through several properties of surface, such as the when the values of the potential evapotranspiration albedo of surface, the temperature of surface, the remain important, with a climax in May (161) vegetation index (LAI, FC over, NDVI) and (DNH-Mali, 1990). The geologic substratum is meteorological data[7], Among these surrounding made of metamorphic and granitic rocks covered areas of remote sensing , we can note the method with washed tropical ferruginous, ferralitic and SEBAL (Surface Energy Balance for Land) hydromorphous grounds. The relief is dominated developed by[2,3,13,14,26], the method S-SEBI by upstream trays to the pond, plains in the center (Simplified Surface Energy Balance Index) and downstream slums the height of which can finalized by, the method SEBS (Surface Energy vary between 315 and 390 m. The vegetation is Balance Système, developed by[15,19,18,26,27,28] characterized by trees, shrubs, meadow, mixed up the method TSEB (Two-Source Energy Balance) with annual agricultures. [8,16,21] [25] proposed a method simplified by the model S-SEBI, based on the concept of the evaporative fraction. This model permits to consider the evapotranspiration from the contrast between the dry and wet areas given by [24], also proposed a method based on the concept of the “eporative fraction”, with a factor of correction of 0.034 on the pond the Indus in Pakistan to estimate the daily evapotranspiration. In the Malian context, the estimation of the evapotranspiration was always made from the conventional methods [32]. Because of the limits observed in the use of the conventional methods, this work is based on the preceding sensing theories. Our survey sets up as objective the estimation and the mapping of evapotranspiration from the satellite pictures AATSR (ENVISAT) developed by ESA (European Spatial Agency) over a period of 8 years, between 2003 and 2010. II. Materials and Methods 2.1 Frame of study: The study concerns the basin of Kolondièba-Tiendaga located in southern Mali Figure1: map of the versant pond of Kolondièba- between the Longitudes and Latitudes 34 °W and 6. Tiendaga 82°W and 10.15°N and 11,08°N. This versant of a 3050 km ², is one sub pond of the cross-border pond of Bani (Fig.1). It is located on the upper pond of Niger, in approximately 262 km from 1600 Bamako (capital of Mali), and is limited to the 1400 North by the city of Kolondièba, to the South by 1200 the municipality of Sibirila until the border of it 1000 Quoted by Ivory, in the East by the municipality of 800 Fakola and Bougoula, on the West by the 600 municipality of Garalo (circle of Bougouni). Its (mm) 400Pluie 200 release is to Tiendaga on the road of Fakola. Its 0 physical characteristics are given in the figure 1. The basin of Kolondièba-Tiendaga has a tropical transition climate or a South Sudan climate, characterized by the alternation of a warm and dry Année season (in November-April) and of a rainy season (May-October) when the rainfall average oscillates 1194 | P a g e DAOU Ibrahima, MARIKO Adama, RASMUS Fensholt, MENENTI Massimo, KOUROSH Khoshelham, MBOW Cheickh, DIALLO Drissa / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue 5, September- October 2012, pp.1193-1200 Figure 2: annual rainfalls recorded on the versant The data produced by ENVISAT will be used basin of Kolondièba-Tiendaga between 1986 and within the framework of the scientific research on 2010 the earth and the monitoring of the environmental Table 1: morphometric characteristics of the and climatic changes. Besides, they will facilitate versant pond the development of operational and commercial applications. The sensor AATSR is one radiometer Designation Value with sweeping with a spatial resolution of 1Km x Longitudes : 1Km, recording 7 spectral ranges in the visible and Outlet 11.066761 the infrared. The track of the sensor AATSR is Latitudes : 6.846652 chosen so as to insure continuity with the sets of data of ATSR1 and ATSR2 of the series of ERS1 Altitude of outlet 313 m and ERS2 of ESA. The characteristics of the sensor Bassin surface 3050 Km2 are given in table 2. Product ATS-TOA level 1P of Main canal’s lenght 158.30 AATSR is used in this work. They were acquired with the European Space agency (E.S.A) in the Hydromorphic Network total lenght 5854.26 framework of the TIGER Initiative on Assessment Strahler Order 7 of Water Resources in Africa under Global Climate Drainage density 1.895 km/Km2 Variability. These data were