Masahiro Tasumi

Integrating satellite-based evapotranspiration with simulation models for irrigation management at the scheme level

Improvements in irrigation management are urgently needed in regions where water resources for irrigation are being depleted. This paper combines a water balance model with satellite-based remote-sensing estimates of evapotranspiration (ET) to provide accurate irrigation scheduling guidelines for individual fields. The satellite-derived ET was used in the daily soil water balance model to improve accuracy of field-by-field ET demands and subsequent field-scale irrigation schedules. The combination of satellite-based ET with daily soil water balance incorporates the advantages of satellite remote-sensing and daily calculation time steps, namely, high spatial resolution and high temporal resolution. The procedure was applied to Genil–Cabra Irrigation Scheme of Spain, where irrigation water supply is often limited by regional drought. Compared with traditional applications of water balance models (i.e. without the satellite-based ET), the combined procedure provided significant improvements in irrigation schedules for both the average condition and when considering field-to-field variability. A 24% reduction in application of water was estimated for cotton if the improved irrigation schedules were followed. Irrigation efficiency calculated using satellite-based ET and actual applied irrigation water helped to identify specific agricultural fields experiencing problems in water management, as well as to estimate general irrigation efficiencies of the scheme by irrigation and crop type. Estimation of field irrigation efficiency ranged from 0.72 for cotton to 0.90 for sugar beet.

Performance assessment of an irrigation scheme using indicators determined with remote sensing techniques.

In this work, remote sensing-based assessments of actual evapotranspiration using METRIC integrated with a water balance model provided accurate estimates of irrigation performance. This new methodology was applied and tested in the Genil–Cabra Irrigation Scheme located in southern Spain during the 2004–2005 irrigation season. The performance indicators used, the annual relative irrigation supply (ARIS) and the irrigation water productivity (IWP), required ET input data which were calculated using either METRIC or standard FAO methodology. The new procedure that used METRIC detected overirrigation (ARIS of 1.27) in situations where the ARIS calculated with the standard FAO methodology indicated near-optimal irrigation (ARIS of 0.98). Additionally, the proposed methodology allows the estimation of the volume of applied water at the field scale. Comparisons between the ARIS and IWP values obtained from actual applied water records against those calculated with the new methodology resulted in good agreement. It is concluded that the integration of the METRIC method to calculate actual ET with a water balance model allowed the determination of performance indicators in an irrigation scheme in a reliable and accurate fashion, requiring only very limited information at the field level.

Estimation of Actual Evapotranspiration along the Middle Rio Grande of New Mexico Using MODIS and Landsat Imagery with the METRIC Model

Estimation of actual evapotranspiration (ET) for the Middle Rio Grande valley in central New Mexico via the METRIC surface energy balance model using MODIS and Landsat imagery is described. MODIS images are a useful resource for estimating ET at large scales when high spatial resolution is not required. One advantage of MODIS satellites is that images having a view angle < ~15° are potentially available about every four to five days. The main challenge of applying METRIC using MODIS is the selection of the two calibration conditions due to the low spatial resolution of MODIS. A calibration procedure specific to MODIS is described that utilizes the higher vegetation index areas of the image along with a consistently low ET location to develop the estimation function for sensible heat flux. This paper compares ET images for the Rio Grande region as produced by both MODIS and by Landsat. Application of METRIC energy balance processes along the Middle Rio Grande using MODIS imagery indicates that one can successfully produce monthly and annual ET estimates that are similar in value to those obtained using Landsat imagery if a cross-calibration scheme is considered. However, spatial fidelity is degraded.

Evaporation from American Falls Reservoir in Idaho via a Combination of Bowen Ratio and Eddy Covariance

Evaporation and energy balance components were measured and estimated for the American Falls reservoir of SE Idaho during 2004. The energy balance for this reservoir that stores snow-melt is dominated by water heat storage that consumes more than one-half of net radiation during the growing season. Evaporation fluxes from the reservoir average less than 40% of alfalfa reference ET, which indicates relatively efficient water storage. Some general relationships between albedo as sensed by satellite and water turbidity and among air and water temperature are presented that may be useful in satellite-based simulation of the energy balance and evaporation processes from the reservoir.

Control of Malaria Mosquito Breeding through Irrigation Water Management

In the dry zone of Sri Lanka, an interdisciplinary study was conducted to evaluate the effects of irrigation water releases on malaria mosquito breeding and to identify different water management options for vector control. The relationship between abundance of larvae of the vector, Anopheles culicifacies (An. culicifacies), and the water level in a stream was described mathematically.An inverse function was derived and incorporated into a water balance model developed for the area. The larval abundance was quantified under different irrigation and water management scenarios. The result demonstrates potential for effective vector control by feasible changes in irrigation management.

Evapotranspiration on the Watershed Scale Using the SEBAL Model and Landsat Images

SEBAL (Surface Energy Balance Algorithm for Land) is an image-processing model comprised of twenty-five submodels that calculates evapotranspiration (ET) and other energy exchanges at the earth’s surface. SEBAL uses image data from Landsat or other satellites measuring thermal infrared radiation, visible and near-infrared. SEBAL was developed in the Netherlands by Bastiaanssen and was modified during this study for mountainous terrain and clear, cold lakes. ET is computed on a pixel-by-pixel basis from an energy balance. The Bear River Basin covers 20,000 km 2 of Idaho, Utah, and Wyoming and contains about 190,000 ha of crop land. ET maps were generated on a monthly basis. The maps show a progression of ET during the year as well as distribution in space. Predicted ET was compared with lysimeter measurements of ET with good results, with monthly differences averaging +/- 16%, but with seasonal differences of only 4% due to reduction in random error.

Use of the METRIC evapotranspiration model to compute water use by irrigated agriculture in Idaho

In 1995, the U.S. Geological Survey estimated consumptive water used by irrigated agriculture accounted for more than 99% of total water use in Idaho. The most recent water-use estimate was done for the year 2000. Unlike previous years, USGS did not report water use by irrigated agriculture. The value of Idahos irrigated agriculture was S2.58 billion in 1997. The Idaho Department of Water Resources wanted water use statistics for 2000, but knew the process would be expensive and time-consuming. A remote-sensing based method, METRIC, offered an alternative solution. METRIC was developed jointly by the University of Idaho and the Idaho Department of Water Resources under a NASA/Synergy grant. METRIC is an evapotranspiration model that uses the visible, near infrared, and thermal infrared bands of any appropriate satellite to compute a complete energy balance for each image pixel. Landsats 7 and 5 were used for this application, with multiple dates processed for nine nominal scenes for the year 2000 in 28 counties of southern Idaho, the region of the state where irrigated agriculture is concentrated. Land in irrigated agricultural was delineated using National Land Cover Data, other data, and thresholding of evapotranspiration values. METRIC computed 9,313,503 acre feet of evapotranspiration from 3,552,174 irrigated acres, or 2.6 acre feet per acre. The irrigated acreage is biased high due to the generalizing affect of the land use/land cover data set. Nevertheless, the results suggest that past water use data may have under estimated consumptive use. The next phase of the study is to compare METRIC-derived evapotranspiration processed from year 2000 MODIS data with the Landsat results

Application of MODIS Land Products to Assessment of Land Degradation of Alpine Rangeland in Northern India with Limited Ground-Based Information

Land degradation of alpine rangeland in Dachigam National Park, Northern India, was evaluated in this study using MODerate resolution Imaging Spectroradiometer (MODIS) land products. The park has been used by a variety of livestock holders. With increasing numbers of livestock, the managers and users of the park are apprehensive about degradation of the grazing land. However, owing to weak infrastructure for scientific and statistical data collection and sociopolitical restrictions in the region, a lack of quality ground-based weather, vegetation, and livestock statistical data had prevented scientific assessment. Under these circumstances, the present study aimed to assess the rangeland environment and its degradation using MODIS vegetation, snow, and evapotranspiration products as primary input data for assessment. The result of the analysis indicated that soil water content and the timing of snowmelt play an important role in grass production in the area. Additionally, the possibility of land degradation in heavily-grazed rangeland was indicated via a multiple regression analysis at a decadal timescale, whereas weather conditions, such as rainfall and snow cover, primarily explained year-by-year differences in grass production. Although statistical uncertainties remain in the results derived in this

Benefits From Tying Satellite‐Based Energy Balance To Reference Evapotranspiration

Satellite‐based surface energy balance is very useful for determining actual evapotranspiration (ET) over large areas. One uncertainty, however, is in regard to the amount of error or bias introduced to the surface energy balance and ET by various calculation components. These include biases in atmospheric correction, albedo calculation, net radiation calculation, thermal band and surface temperature, air temperature gradient used in sensible heat flux calculation, soil heat flux function, and extrapolation to 24‐hour and longer periods. At the University of Idaho, we use calculated hourly reference evapotranspiration (ETr) to calibrate the surface energy balance during processing and to remove these biases. In addition to its use to calibrate the energy balance, ETr is used to extrapolate ET images to 24‐hour and longer periods. The use of ETr provides equivalency and congruency with ET as estimated using the traditional crop coefficient × ETr approach.

Integration of satellite-based energy balance with simulation models applied to irrigation management at an irrigation scheme of southern Spain

This paper combines a water balance model with satellite-based remote-sensing estimates of evapotranspiration (ET) to provide accurate irrigation scheduling guidelines for individual fields. The satellite-derived ET was used in the daily soil water balance model to improve accuracy of field-by-field ET demands and subsequent field-scale irrigation schedules. The combination of satellite-based ET with daily soil water balance incorporates the advantages of satellite remote-sensing and daily calculation time steps, namely, high spatial resolution and high temporal resolution. The procedure was applied to Genil - Cabra Irrigation Scheme in Spain, where irrigation water supply is often limited by regional drought. Compared with traditional applications of water balance models (i.e. without the satellite-based ET), the combined procedure provided significant improvements in irrigation schedules for both the average condition and when considering field-to-field variability. A 24% reduction in water use was estimated for cotton if the improved irrigation schedules were followed. Irrigation efficiency calculated using satellite-based ET and actual applied irrigation water helped to identify specific agricultural fields experiencing problems in water management, as well as to estimate general irrigation efficiencies of the scheme by irrigation and crop type. Estimation of field irrigation efficiency ranged from 0.72 for cotton to 0.90 for sugar beet.