Assessment of crop productivity for major river basins in asia
using GIS and RS data
Keywords: NPP, Crop production, NDVI, Remote Sensing, GIS
Abstract:
The land use / land cover has been dramatically changed in Asian countries in the last a few decades caused by the population pressure. Generally, the forested lands have been converted to agricultural lands, as well as the productivity has been improved because of irrigation, chemical fertilizer, mechanization and so on. The agricultural production has increased for many years in the region to support the population. However, there arises a doubt that there must exist a limit of sustaining the regional population based on agricultural production. In this study, the estimation of agricultural production reflecting the current land use / land cover in the major river basins in Asia, has been investigated.
The agricultural production is considered to be a part of Net Primary Production(NPP) on the agricultural land. The NPP can be estimated using Photosynthetically Active Radiation(PAR) and NDVI, that can be derived from Satellite data. The distribution of agricultural land can be seen in the land use/land cover map. The NPP on the agricultural land of major river basins in Asia was estimated with these dataset. Moreover, by integrating the result of the agricultural NPP with the statistics of country based crop production, the conversion efficiency of agricultural production from agricultural NPP was made. Finally, per capita productivity is analyzed in the region.
1. Introduction
By the UN announcement, world population reaches 6 billion in October 1999. According to the FAO statistics, the crop production has increased corresponding to the population increase in the last 40 years. However, optimistic forecasting of crop production can not be expected, because there are limit of suitable crop land, limitation of productivity and shortage of water resources. Monitoring, estimating and forecasting crop production are quite important for the management of world, regional or local food demand and supply balance. A method to monitor and estimate per capita productivity using remote sensing data and Geographic Information System(GIS) is applied in this study for the region of major river basins in Asia.
2. Processing flow and data used
Figure-1 shows the flow of data processing in this study. There are three kind of source data. Map data include (1) Digital Elevation Model(DEM), (2) River Network Map and (3) Administration Boundary. Statistical data include (4) Agricultural Production and (5) Population. Satellite Data include (6) Land Cover data, (7) Normalized Vegetation Difference Index(NDVI) and (8) Photosynthesis Active Radiation (PAR) Data.
Crop Land Suitability map is generated using DEM based on information of land altitude and slope gradient. Drainage model was generated using DEM(GTOPO30) and River Network Information. The drainage model can extract catchment area of major rivers in Asia such as Amur river, Yellow river, Yangzhu river, Mekong river, Ganges river and Indus river. And the drainage model has consistent flow direction in each pixel from top stream to the bottom of the river. By using the drainage model, each pixel can be identified where is the catchment of the pixel and where to flow to the down stream(Ochi and Shibasaki, 1999). Net Primary Productivity(NPP) is estimated using NDVI and PAR data(Monteith, 1977).
Crop production analysis is made using administrative boundary, statistics of agricultural production
Figure-1 Flow of Data Processing
and population, land cover data and NPP. Finally, per capita crop production analysis is made using crop land suitability map, drainage model and the output of crop production analysis. The detail of the source data is described as follows:
(1) Digital Elevation Model(DEM): GTOPO30, which is 30 second arc resolution(approx. 1km resolution) produced by U.S. Geological Survey(USGS). The data can be downloaded from internet URL : http://
edcdaac.usgs.gov/gtopo30/gtopo30.html.
(2) River Network and (3) Administrative boundary map: Rasterized River Network image is generated from Digital Chart of the World(DCW) using ARC/Info - "linegrid" - command. The DCW data can be downloaded from internet URL: http://
www.nima.mil/publications/guides/dtf/dcw.html.
(4) Agricultural Production: Agricultural production data is retrieved from FAOSTAT Agricultural Data URL: http://
apps.fao.org/. In this study, "cereal production" is used to represent agricultural production.
(5) Population data: CIESIN(Consortium for International Earth Science Information Network) provides 5 minutes population data which were interpolated from the population census in 1994. The CIESIN URL is http://
www.ciesin.org/.
(6) Land Cover Data: Land cover data were retrieved from USGS Global Land Cover Characteristics Data Base retrieved at the URL: http://
edcwww.cr.usgs.gov/landdaac/glcc/glcc_na.html. There are 6 maps in different schemes in the data base, and IGBP Legend map was used in this study.
(7) NDVI Data: Monthly NDVI data from January 1982 to December 1993 were composed using 8km resolution 10 days composite data set given as NOAA/NASA Pathfinder AVHRR Land Data Set.
(8) PAR Data: One degree monthly Photosynthesis Active Radiation(PAR) data from January 1979 to December 1989 were provided using TOMS satellite data(Dye et al, 1993). In this study, interpolated 8km resolution averaged monthly PAR data were used in order to calculate NPP of 1981 to1989.
