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Poster Session 2
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Assessment of crop productivity for major river basins in asia
Using gis and rs data
4. Analysis and simulation
4.1 Per capita productivity
Per capita productivity is defined for each pixel as follows.
- Catchment area for a pixel along a river is defined using drainage model .
- Accumulated population in the catchment area is calculated for the pixel.
- Accumulated Cropland NPP(CNPP) in the catchment area is calculated for the pixel.
- Per capita productivity is calculated by dividing the accumulated CNPP by the accumulated population for the pixel.
- Per capita productivity is calculated for all pixels of the six major river basins in Asia.
Figure-5 and Table-3 show the per capita productivity - relation between accumulated CNPP and accumulated population - from the upper stream of the river basin to the bottom of the basin for these six river basins. The slope of the regression line means per capta productivity. Per capita production is an indicator to evaluate the potential or population carrying capacity, because the indicator can show how much cropland NPP is produced/consumed for one person in the basin. So, if the per capita productivity is big, it means that the basin is more rich than the basin with small per capita productivity.
CNPP = a × Population ............(4)
where a: per capita CNPP
Figure-4 Relation between CNPP and Population in 6 Major River Basins in Asia
Table-3 Per capita productivity for 6 major river basins in Asia
| Basin |
Per capita CNPP(top/cap) |
Productivity |
| Mekong |
9.09 |
High |
| Amur |
3.46 |
Medium |
| Indus |
3.46 |
Medium |
| Ganges |
1.93 |
Low |
| Yangzhu |
1.22 |
Low |
| Yellow |
0.95 |
Low |
4.2 Simulation
Carrying capacity based on crop(cereal) production were estimated for these six river basins as shown in Table-4. Cropland areas were measured from USGS/IGBP land cover map for each river basin. Potential cropland was estimated by assuming if a half of existing forested area were converted to cropland. Because the Mekong and Amur river basins remain large amount of forest land, these two basins have more potential of cropland rather than other four basins where most land of the basins are already used for cropland or grassland. "Potential of per capita productivity" means that how many population can be supported by one unit of C-NPP in case one unit of C-NPP can support the same population realized in Yangzhu river basin(820 persons per ton of C-NPP). The current population was measured from CIESIN population data. The output shows that Mekong river basin can support about 13.9 times of the current population in the basin. On the contrary, Yangzhu river and Yellow river basin can support about 1.2 and 1.3 times respectively of the current population in the basins.
Table-4 Population Carrying Capacity in Six Major River Basins
| Basin |
Cropland area (1000sq.km) |
Potential croplan*(%) |
Potential of per capita productivity (%) |
Current Population(million) |
Potential Population(million) |
| Mekong | 266.1 |
159 | 745 |
45.2 | 535 | (1185%) |
| Amur | 233.3 | 314 | 284 | 60.6 | 540 | (892%) |
| Indus | 370.7 | 101 | 174 | 172.8 | 302 | (175%) |
| Ganges | 638.3 | 104 | 158 | 340.2 | 558 | (164%) |
| Yangzhu | 617.4 | 108 | 100** | 414.2 | 447 | (108%) |
| Yellow | 151.9 | 105 | 77 | 135.2 | 109 | (81%) |
Remarks : * a half of forest land is assumed to be converted to cropland
** per capita CNPP is assumed same as of Yangzhu River Basin
5. Conclusions and Further Studies
In this study, Satellite RS and GIS are used to estimate NPP and Population Capacity in major river basins in Asia. Most of the input data can be down loaded through internet or access-free CD-ROM. The procedure can work to other regions in the world in any scale from local to global, and can be applied using updated satellite data. The result shows that Mekong and Amur River basins have the highest population carrying capacity under the above-mentioned assumptions, while Yangzu and Yellow River basins are saturated. In the previous study about global population carrying capacity, it was not clear how many, where and how people can survive on the land. The output is very useful to understand the future status of the population distribution in the region and to plan the strategy for land use/agricultural development.
There remain some problems to be solved in the procedure. Firstly, in the algorithm to estimate NPP using NDVI and PAR, e(efficiency parameter ) is set to 1.5 as a global average. However, the efficiency is considered to vary depending on the climate condition and vegetation type. Secondly, it was assumed that per capita productivity for all river basins in Asia can attain to the level of Yangzhu river basin in the simulation procedure. However, per capita productivity must have unique value depending on the region specified by the climate, cultivation style etc. The regional characteristics of per capita productivity should be investigated through further studies.
Reference
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Dye, D.G., Goward,S. and Eck, T.F., Global Solar Radiation Data Set for Global Primary Production Studies, Proceedings of SEIKEN SYMPOSIUM-Vol.12 " , pp41-47, 1993.
- Goward, S.N. and Huemmrich, K.F., Vegetation Canopy PAR Absorptance and the Normalized Difference Vegetation Index: An Assessment Using the SAIL Model, Remote Sensing of Environment, 39, pp119-140, 1992.
- Monteith, J.L., Climate and the efficiency of crop production In Britain, Philophical transactions of the Royal Society of London, Ser. B, 281, pp277-294, 1977
- Ochi,S. and Murai, S., , " Analysis of relationship between NPP and Population carrying capacity for major river basins in Asia, Proceedings of 9th SEIKEN Forum "Global Environment Monitoring from Space", pp258-262, 1999.
- Ochi,S, and Shibasaki, R., Algorithm for Generating Drainage Direction Matrix using DEM(GTOPO30) and DCW, Journal of the Japan Society of Photogrammetry and Remote Sensing, Vol38, No.3, pp60-68,1999.
- Ruimy, A., Saugier, B. and Dedien, G., Methodology for the estimation of terrestrial net primary production from remote sensed data, Journal of Geophysical Research, 99, pp5266, 1994.
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