Dr. Chris Perry, Cranfield University, United Kingdom
“Irrigation reliability and the productivity of water: a proposed methodology using
evapotranspiration mapping” (Presention [online|pdf], paper)
Abstract
Irrigation is the dominant user of water world wide, but provision of potable water and water for industry are higher priorities and give higher social and economic returns. Irrigation will continue to lose water to competing sectors and the productivity of irrigation systems (since food demand continues to grow) remains a central issue in water management. Performance assessment of irrigation has traditionally been difficult when based on field measurements of flows, deliveries and depths over large areas. Furthermore, performance measures have shifted from narrow engineering indicators to broader productivity issues of production achived per unit of water consumed. Remote sensing, applied to the measurement of ET over large areas, provides analysts of irrigation systems with extraordinary new tools for the objective assessment of consumption and production – constituting a quantum leap in the assessment of irrigation system performance. Utilisation of these tools is spreading rapidly, but important areas remain to be “converted” from traditional approaches that rely on an array of estimated parameters. The next challenge for remote sensing will be to map the frontier between the reliability of the irrigation service and the productivity achieved. Reliability provides the inducement for farmers to invest in higher productivity – to the benefit of themselves and society – and understanding better how the individual maximises profits within an uncertain irrigation environment can provide important guidance to managers and system designers.
Dr. Luis Pereira, Departamento de Engenharia Rural, Instituto Superior de Agronomia, Lisbon, Portugal
“Water consumption and quantification issues in sustainability of irrigated agriculture” (Presentation [online|pdf] no paper)
Dr. Massimo Menenti, L. Jia, and Z. Su. Istituto por lo Studio dei Problemi Agronomici dell’Irrigazione nel Mezzogiorno (ISPAIM), Naples, Italy, and Louis Pasteur University of Strasbourg, France
“On SEBI-SEBS validation in France, Italy, Spain, USA and China” (Presention [online|pdf], paper)
Abstract
The Surface Energy Balance Index is a normalized measure of relative evaporation based on relating observations of surface temperature to theoretical upper and lower bounds on the difference between surface and air temperature. More recently, the SEBI concept has been embedded in the Surface Energy Balance System (SEBS) by Su (2001, 2002). The reference height of air temperature is chosen to be representative of mean boundary layer over heterogeneous land surfaces. Observations of land surface temperature and shortwave reflectance are typically obtained by space- and airborne sensors. Estimates of latent and sensible heat flux density and of evaporative fraction may be obtained from SEBI – values. The paper summarizes results obtained in the context of validation experiments carried out in France, Italy, Spain, USA and China at local and regional spatial scales. At larger spatial scales, i.e. for the experiments in Spain, USA and China surface temperature and shortwave reflectance have been determined using the radiometric data obtained with AVHRR and the Along Track Scanning Radiometer (ATSR). To validate estimate of sensible heat flux density at larger spatial scales, extensive use of Large Aperture Scintillometers has been made. Agreement with observations was fair to good, notwithstanding the difficulty of estimating some SEBI parameters, such as the aerodynamic resistance for sensible heat transfer.
Drs. A.S.M. Gieske and W. Meijninger, International Institute for Geo-Information Science and Earth Observation ITC, Enschede, The Netherlands
“High density NOAA time series of ET in the Gediz Basin, Turkey” (Presention [online|pdf], paper)
Abstract
An evapotranspiration method comparison study was carried out by the International Water Management Institute (IWMI, Sri Lanka), at two locations in the Gediz Basin, Turkey, in the period from May until September 1998. A number of ground-based techniques were compared with results obtained by remote sensing methods. Recently, a search of the Satellite Active Archive yielded over 70 high quality level 1b images of the same time period. The processing of these images with the SEBAL algorithm enabled us to build up a detailed time series of sensible and latent heat fluxes for a period of 120 days. In this study a comparison is made between the sensible and latent heat fluxes determined from the present series of NOAA-14/AVHRR images and the results obtained earlier in the 1998 IWMI project.
Drs A. Olioso, Y. Inoue, S. Ortega-Farias, J. Demarty, J.P. Wigneron, I. Braud, F. Jacob, P. Lecharpentier, C. Ottlé, J. Calvet, and N. Brisson. INRA CSE, Domaine Saint-Paul, Avignon, France
“Assimilation of remote sensing data into crop simulation models and SVAT models” (Presention [online|pdf], paper)
Abstract
Soil-Vegetation-Atmosphere Transfer models (SVAT) and Crop Simulation models describe physical and physiological processes occurring in crop canopies. Remote sensing data may be used through assimilation procedures for constraining or driving SVAT and crop models. We developed the coupling between crop, SVAT and radiative transfer models in order to implement assimilation procedures in various wavelength domains (solar, thermal and microwave). Simple assimilation tests are presented in order to illustrate the main techniques that may be used for monitoring crop processes and evapotranspiration.
Drs. Dominique Courault, Bernard Seguin, and A. Olioso, INRA CSE, Domaine Saint-Paul, Avignon, France
“Review to estimate evapotranspiration from remote sensing data: some examples from the simplified relationship to the use of mesoscale atmospheric models” (Presention [online|pdf], paper)
Abstract
Different methods have been developed to estimate evapotranspiration from remote sensing data. Among them direct methods based upon the energy balance equation and using thermal infrared (TIR) data like the simplified relationship. This method has been applied for various situations: from small spatial scale using airborne TIR images to continental scale with NOAA data. More recently indirect estimates using assimilation procedures and Soil-Vegetation-Atmosphere Transfer (SVAT) models have been developed. In this last case, the combination of different wavelength domains is often required so as to get input parameters of these models to characterize the different surfaces like albedo, emissivity or Leaf Area Index. A brief review of these different approaches is presented. Some examples are shown on the site of the Alpilles Reseda project, where various types of models (Sebal, Meso-NH...) were used to estimate surface fluxes from remote sensing data. The main physical bases and assumptions of these models are also discussed in this paper.
Dr. Wim Bastiaanssen and N. Harshadeep, Water Watch, Wageningen, The Netherlands
“Managing scarce water resources in Asia: the nature of the problem and can remote sensing help ?” (Presention [online|pdf], paper)
Abstract
Water demand exceeds the water supply in the vicinity of fast expanding super metropolitans found on the alluvial plains of Asia. A fierce competition for water between the urban, industrial, agricultural and environmental users has began. Several basins exploit groundwater as a remedy to surface water resources scarcity, but this leads to unsustainable developments. Water policy makers have, therefore, to work out strategies for integrated water and environmental management, which rely on a proper knowledge of the basin hydrological and pollution conditions. Examples from various countries in Asia are elaborated in this paper to demonstrate how spatially distributed evapotranspiration data from remote sensing, in conjunction with other key data, can help to build the knowledge base for integrated basin scale water management. Remote sensing is not a solution, but, it provides key data that is difficult to access by conventional methods.
Dr. J. Garatuza Payán and Christopher J. Watts, Instituto Tecnológico de Sonora, Obregón, Son., Mexico
“The use of remote sensing for estimating ET in NW Mexico” (Presention [online|pdf], paper)
Abstract
Components of a satellite-based system for estimating the crop water requirements of irrigated vegetation have been combined, applied, and tested against field data in the Yaqui Valley, northwest Mexico. Frequent satellite observations have the potential to provide snap shots of cloud variability at high spatial and temporal resolutions that are needed for making simple, near real-time estimates of incoming solar radiation and, thus, daytime evaporation required for irrigation scheduling. Less frequent polar orbiting satellites offer the capacity of following the vegetation development at higher spatial resolution. The operational framework for obtaining cloud cover has been developed and applied using hourly sampled, 1 km resolution, GOES-10 data received in real-time. The high-resolution, cloud-screening algorithm has proved to be efficient and reliable and has been used to provide high-resolution (4 km) estimates of solar radiation.
Relationships between vegetation indices (NDVI and SAVI) and crop coefficients (the ratio of measured to potential evapotranspiration) have been derived with four different models (Shuttleworth, Penman, Priestley-Taylor and Makkink), using ground based surface reflectance measured over the crop. Continuous measurements of surface fluxes and other meteorological variables were made following almost the entire vegetative cycle of the plant using a station equipped with standard meteorological instruments and an eddy-correlation system. Actual evapotranspiration was computed as the product of the estimated crop coefficients, derived from field radiometer measurements, and potential evapotranspiration. In comparison with ground data, RMSE values are on the order of 1 mm per day. Finally the opportunity to use high-resolution satellite data to make near real-time estimates of crop evaporation is discussed.
Dr. Christoper M.U. Neale, Hari Jayanthi, and James L. Wright, Utah State University, Logan, Utah,
USA
“Crop and irrigation water management using high resolution airborne remote sensing” (Presention [online|pdf], paper)
Abstract
This paper offers a historical retrospective on the remote sensing of crop coefficients for obtaining actual crop evapotranspiration. We present recently developed crop coefficients for bean and potato and show the usefulness of high-resolution airborne imagery for monitoring temporal changes and characterizing in-field variability of crop growth.
Dr. Richard G. Allen, A. Morse, and M. Tasumi. University of Idaho, Kimberly, Idaho, USA
“Application of SEBAL for western US water rights regulation and planning” (Presention [online|pdf], paper)
Abstract
Quantifying evapotranspiration (ET) from irrigated projects is important for water rights management, water resources planning and water regulation. Traditionally, ET from agricultural fields has been estimated by multiplying the weather-based reference ET by crop coefficients (Kc) determined according to the crop type and the crop growth stage. However, there is typically some question regarding whether the crops grown compare with the conditions represented by the Kc values, especially in water short areas. In addition, it is difficult to predict the correct crop growth stage dates for large populations of crops and fields. Recent developments in satellite remote sensing ET models have enabled us to accurately estimate ET and Kc for large populations of fields and water users and to quantify net ground-water pumpage in areas where water extraction from underground is not measured.
SEBAL (Surface Energy Balance Algorithm for Land) is an image-processing model comprised of twenty-five submodels for calculating evapotranspiration (ET) as a residual of the surface energy balance. SEBAL was developed in the Netherlands by Bastiaanssen and was extended during Idaho applications for mountainous terrain and with tighter integration with ground-based reference evapotranspiration. SEBAL has been applied with Landsat images in southern Idaho to predict monthly and seasonal ET for water rights accounting and for operation of ground water models. ET "maps" (i.e., images) via SEBAL provide the means to quantify, in terms of both the amount and spatial distribution, the ET on a field by field basis. The ET images generated by SEBAL show a progression of ET during the year as well as distribution in space.
ET from satellite images may ultimately replace current procedures used by state departments of Water Resources and other management entities and ministries that rely on ground-based ET equations and generalized crop coefficients that have substantial uncertainty. Initial application and testing of SEBAL indicates substantial promise as an efficient, accurate, and inexpensive procedure to predict the actual evaporation fluxes from irrigated lands throughout a growing season.
Drs. Anne Jochum and Alfonso Calera, DEMETER, ALFAclima Asesoramiento Medioambiental,
Albacete, Spain.
“Space-assisted irrigation management: towards user-friendly products” (Presention [online|pdf], paper)
Abstract
Irrigation Advisory Services (IAS) are the natural management instruments to achieve a better efficiency in the use of water for irrigation. IAS help farmers to apply water according to the actual crop water requirements and thus, to optimize production and cost-effectiveness. The project DEMETER (DEMonstration of Earth observation TEchnologies in Routine irrigation advisory services) aims at assessing and demonstrating how the performance and costeffectiveness of IAS is substantially improved by the incorporation of Earth observation (EO) techniques and Information Society Technology (IT) into their day-to-day operations. EO allows for efficiently monitoring crop water requirements of each field in extended areas. The incorporation of IT in the generation and distribution of information makes that information easily available to IAS and to its associated farmers (the end-users) in a personalized way. This paper describes the methodology and first results.
Mr. Satyanto K. Saptomo, Yoshisuke Nakano, Tomokazu Haraguchi, Kozue Yuge, and Masaharu Kuroda, Laboratory of Irrigation and Water Utilization, Kyushu University, Fukuoka, Japan.
“The modification of a numerical evapotranspiration model by using remotely sensed surface temperature data” (poster not available, paper)
Abstract
ET for large area with different land covers were estimated by evaluating energy balance components for each land use, using numerical model of energy balance which includes differential equations of wind velocity, specific air humidity, potential air temperature, soil temperature and soil moisture. Remotely observed surface temperatures were used to modify the parameters used within the model. The inputs for this model are direct and diffused solar radiation, solar elevation, long wave radiation, surface temperature, ground moisture, crop transpiration resistance, leaf area index, crop canopy architecture, wind velocity, air temperature and relative humidity at surface and at boundary height. The extinction of solar radiation intensity as it passes the land cover canopy is estimated by treating the plant canopy as a single ‘big leaf’. As for the upper boundary of this system, constant values of wind velocity, potential air temperature, and specific humidity were used at the height of 100 m above ground surface. The lower boundary was taken at 0.5 m depth under ground surface. This technique is applied for conducting numerical experiment to estimate ET temporal and spatial distribution over different land uses at the area of Cidanau watershed, Banten, Indonesia. Land utilizations at the study location are artificial surface, paddy field, bare soil and forest. In this study, evapotranspiration estimated in artificial surface, bare soil, paddy field and forest are 0, 4.5, 5 and 6 mm/day respectively.
Drs. Masahiro Tasumi, Ricardo Trezza, Richard G. Allen, and J.L. Wright, University of Idaho, USA and
University of the Andes, Merida, Venezuela.
"US Validation tests on the SEBAL model for evapotranspiration via satellite” (Poster [online|pdf], paper)
Abstract
SEBAL (Surface Energy Balance Algorithm for Land) is a widely applied remote-sensing evapotranspiration (ET) estimation model. This paper presents the results of two validation studies of SEBAL applications in the western United States, with some results of sensitivity and repeatability analyses. The validation studies show that the ET estimated by SEBAL corresponded well with lysimeter measured ET for agricultural crops in the semi-arid climate. Sensitivity analyses on impacts of atmospheric correction for surface temperature and albedo showed that the internal calibration procedures of SEBAL compensated well for errors in temperature and albedo when atmospheric correction was not made. Therefore, users can avoid applying complex and time-consuming atmospheric correction procedures with SEBAL. A repeatability test by two totally independent applications using different images, operators and weather datasets, shows that seasonal estimation by SEBAL has a high repeatability (i.e. stable for the differences of satellite image timings, operators preferences and input weather datasets). We also demonstrate that SEBAL results can be used as a means to confirm traditionally applied crop coefficient curves.