Detection of preparatory water in paddy irrigation area 
using RADARSAT/SAR-C and Landsat/ETM+ 
Shigeo Ogawa 3,*, Takeo Shima a, Hisashi Takeichi ^ 
NIRE, Department of Regional Resources, 2-1-6, Kannondai, Tsukuba, Ibaraki, Japan — sogawa(@affre.go.jp 
MAFF, Kisogawa Management Office, 3-11-16, Shirogane, Showa, Nagoya, Aichi, Japan — takeichi_hisashi@tokai.nn-net.go.jp 
  
Working Group VII/2 
KEY WORDS: Remote Sensing, Crop, SAR, Optical, Accuracy, Multitemporal 
ABSTRACT: 
Paddy rice is one of the most important crops in Japan and it needs much water to grow, especially for water reserves for paddy 
irrigation. The test site “Owari Seibu” doesn’t have enough irrigation water and the water reserves are rotated for a period of about 
one month in this area. In order to monitor the water reserves condition, we use four satellite data sets (RADARSAT/SAR-C, 
Landsat/ETM+) and a digital land use map (10m mesh). Relationship between total of estimated paddy field area from satellite and 
statistical value is very high (n=32, y=1.12x, r’=0.999). The results of detecting transplanted paddy field area accurately correspond 
to statistical data (n=18, r°=0.990) at the local level. The distribution map of water reserves made from this analysis shows a rotation 
pattern over a wide area. 
1. INTRODUCTION 
Paddy rice needs much water to grow and farmers derive 
water in rotation rule that has established from ancient period. 
Preparatory water in paddy irrigation is needed much water in 
short time. Rotation rule is strict in preparatory water term. 
Irrigation water is rotated in test site “Owari seibu area” for 
preparatory water. The term of preparatory water in paddy 
irrigation is about one month. Distribution of paddy field is 
decreasing by the construction of building or the control of 
production by the government. It takes many costs to monitor 
the distribution of water irrigation in wide area. In order to 
monitor the water reserves condition, we use four satellite data 
sets (RADARSAT/SAR-C, Landsat/ETM-) and a digital land 
use map (10m mesh). 
There are many papers on the detection of paddy field area. 
Nageswara and Rao (1987) estimated the paddy area and yields 
in India using Landsat/TM. Otsubo and lida (2001) made time 
map in lower Mekong area using 
flood 
series 
198 
RADARSAT/SAR data. But, they didn't validate the amount of 
area. Fujiki et al. (2001) analyzed water management of paddy 
field based on field survey and hearing on upper east bank of 
Thao Phraya Delta, Thailand. 
Yamagata et al. (1988) analyzed paddy field area by the 
methods of most likelihood classification and filtering. 
Estimation of paddy field area is in 52ha (2.5%) RMSE. Ogawa 
et al. (1990) got high accuracy of paddy area estimation by 
calculating the percentage of branch road, farm ditch, ditch 
border and levee area. Okamoto et al. (1996) estimated paddy 
field area from the relationship between band5 of Landsat/TM 
and RVI. 
There are few papers on preparatory water in paddy 
irrigation, because it takes some time series satellite data to 
monitor preparatory water in preparatory water season. 
We estimated preparatory water distribution and area based 
on field survey and characteristics of back scatter coefficient. 
We validated then from statistical data. 
  
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