Estimation of Rice Evapotranspiration in Paddy Fields Using Remote Sensing and Field Measurements
Water resources are limited in many parts of the world. Due to the fast growing world population, the demand for domestic and industrial water use is increasing tremendously. This results in reduction of water for agricultural use, especially for major rice growing areas which needs huge amounts...
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| Main Author: | |
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| Format: | Thesis |
| Language: | English English |
| Published: |
2005
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/5988/1/FK_2005_10.pdf |
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| Summary: | Water resources are limited in many parts of the world. Due to the fast growing world
population, the demand for domestic and industrial water use is increasing tremendously.
This results in reduction of water for agricultural use, especially for major rice growing
areas which needs huge amounts of water. The study was carried out in the northwest of
Selangor, in the Tanjung Karang Rice Irrigation Project Malaysia. The objectives of this
study were to estimate the rice evapotranspiration using satellite data and compare it with
the field measurements. Eight sets of non-weighing lysimeters (91 cm x 91 cm x 61 cm)
with attached casella hook were installed to measure the crop evapotranspiration at five
different locations within the 19000 ha rice irrigation scheme. Global positioning system
(GPS) was used to locate the lysimeter position. The rice yields in the lysimeters were
manually measured for three seasons. An automatic meteorological station was installed
inside the field to collect data required for calculations of the crop evapotranspiration
using the CROPWAT software. NOAA satellite data was used as data input to correlate
the remote sensing data with field evapotranspiration data. For three seasons, the off (dry)season from December to May, the main (wet) season from July to November, the
observed ET from the lysimeters ranged from 3.2 to 5.8 mmlday, while ET by calculation
using weather parameters ranged from 3.15 to 5.72 mmlday. There was no significant
difference between the blocks in the first season of the experiment because of the small
area and not much difference in the environmental conditions within the block. Most of
the correlation for the second and the third season were significant at 0.01%. The
corresponding ET values from satellite data were 4.04 to 6.54 mmlday. Considering ET
measured by lysimeter as the most accurate method, ET determined using satellite data
overestimates and by computed method underestimates those obtained by lysimeter. ETc
by NOAA data were found to overestimate by 8% to 12% with an average of 10%. Using
CROPWAT, ETc were found to be underestimated between 7% and 20% with an average
The significance findings of this research are that ET can be estimated for paddy areas in
Malaysia with reasonable accuracy using satellite data or computed method. The
implications are that much time and cost can be saved using these alternative techniques
compared to manual data collection from lysimeters. This will result more efficient water
management planning in the rice areas.
Generally, by knowing the actual ET, the cropping calendar can be prepared at the
beginning of the cultivation season by knowing the amounts of water needed throughout
the season. |
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