Remote sensing of environment and disaster laboratory

Institute of Industrial Science, the University of Tokyo, Japan

DEVELOPING GLOBAL CROP WATER REQUIREMENTS BY INTEGRATINGREMOTE SENSING DATASETS AND FAO-CROPWAT MODEL
Anjar Dimara Sakti and Wataru Takeuchi
Institute of Industrial Sciences, University of Tokyo, Japan

Abstract
Currently, almost 90% of global water consumption is for irrigation purpose. Many researchers studied water budget in the global
ecosystem field but many of them were not focus on analyzing water budget for cropland area purpose. One of the study regarding
global irrigation water budget did not use crop stage calendar and has a coarse spatial resolution (0.5 degrees), therefore developing
higher resolution which includes crop stage analysis is needed. The increasing availability and reliability of satellite remote sensing
product make it feasible to estimate the global terrestrial crop water requirement (CWR) at fine spatial resolution. To assess global
crop water situation, we generate 1km high-resolution global crop water requirement product by combining various remote sensing
product and FAO-CROPWAT model. Global CRW product is projected to simulate global crop water budget that is more realistic byconsidering plant growth phase with higher pixel resolution. This high resolution of global CWR can be utilized not only in global scale
but also in regional and country scale, also can be analysed in major River basin area. Crop stage additional data that was converted
into Kc value becomes an added-value in developing this global CWR product compared to the previous product so that it is projected
to produce a more realistic product for stimulating global crop water requirement.
Keywords: global crop water requirement, FAO-CROPWAT model, crop-evapotranspiration

Introduction
For the assessment of future water andfood situation, it is necessary to estimate
the water requirement of agriculture.
‘‘Water requirement’’ means the amountof water that must be applied to the cropby irrigation to achieve optimal crop
growth. Modelling of today’s irrigationwater requirements as a function ofirrigated crop area, climate, and crops
stage phase provides the basis for
estimating future impact of climate change
as well as demographic, socioeconomic,and technological changes.

Results and Discussion
A. Global crop coefficient (Kc) distribution (For Single, double and triple Cropping – with Rice and Non-Rice Paddy)

Water balance of the root zone. Image source: FAO

B. Total Global Crop Water Requirement in 2010

Methodology
Overall flowchart of this study

CROPWAT Kc and water requirement result for rice paddy

Conclusions
Data description for developing the global crop water requirement (CWR)

The study result shows that integrating satellite remote sensing product combine with FAOCROPWAT model could be applicated in estimating the global terrestrial crop water requirement(CWR) at fine spatial resolution. To enhance the accuracy of CWR in rice paddy area, calculating
specific water consumption during land preparation stage for Rice paddy will be included in next
CWR processing. MODIS NDVI and LSWC AMSR2 spatiotemporal datasets utilization as reference
to measure accuracy of global distribution Kc and net irrigation value is the originality in this study.

References
1. Petra Doll,P and Siebert, S. Global modelling of irrigation water requirements. Water Resources Research, Vol. 38, NO. 4,, 2002
2. Smith, M., CROPWAT – A computer program for irrigation planning and management, Irrigation and Drainage Pap. 46, Food andAgric. Org. of the U. N., Rome, 1992.

For further details, contact: Anjar D Sakti, Bw-601, 6-1, Komaba 4-chome, Meguro, Tokyo 153-8505 JAPAN (URL: http://wtlab.iis.u-tokyo.ac.jp/ E-mail: anjar@iis.u-tokyo.ac.jp)