El Nino Damage Assessment in Central Luzon using
Multitemporal Remotely-Sensed Images
Analysis and Interpretation of Data
An analysis of the classified images revealed the different land uses of the study area. The 1990 and 1997 images showed substantial agricultural land uses. Most agricultural lands were planted by rice. Most of the lands can be considered as irrigated wet and dry.
As for the non-agricultural land uses, the most prominent in the 1990 and 1997 images is the built-up areas surrounding San Fernando.
In both years (1990 and 1997), the effects of El Nino on the agricultural lands were obvious. The images showed that a large part of the agricultural lands were not cultivated because of the lack of rain and water from irrigation systems. The 1997 images show that rainfed lands and most of irrigated lands were not planted with rice. For the irrigated supply from the water dams servicing the area. For instance, water level in the Pantabangan Dam in Nueva Ecija dropped to 181:7 meters above sea level, or 39.3 meters below the desired level. Likewise, water in the Angat Dam in Bulacan dropped to 185.58 meters from its normal level of 212 meters (Reuter, 1997). Both dams supply water to irrigate agricultural lands in Central Luzon.
In terms of the changes in land use, the effect in agricultural lands in 1990 was greater in area than for non-agricultural lands. In 1997, there was a relative decrease in area of cultivated areas in San Fernando. This meant decrease in agricultural production. Also, there was a decrease in the volume of fish catch because most ponds dried up (Morales, 1997).
While the images reflect a minimal increase in built-up areas between 1990 to 1997, cultivated areas decreased because of the entry of lahar from Mt. Pinatubo in portions of the study area. Another factor is the destruction of irrigation systems in the area due to flooding. A third factor is the reduction of the volume of water supplied by the dams for irrigation.
Conclusion
The study generated up-to-data land use maps showing affected and non-affected agricultural lands of the study areas. Based on the maps, it can be concluded that the agricultural lands of San Fernando decreased in area from 1990 to 1997.
The factors that affected the decrease in the areas of agricultural lands include the lack of adequate water supply, especially during the occurrence of El Nino, encroachment of lahar and land conversion. The decrease of cultivated agricultural lands translates to a corresponding decrease in agricultural production. Other factors that led decrease in agricultural production include lack of systematic irrigation network and lowering of water levels in most dams.
Acknowledgement
The author gratefully acknowledges the kind assistance of NASDA RESTEC of Japan for the availability of the MOS-1 and ADEOS images.
References
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Balababa, L. et. al. Identification of Rice Cropping Areas in the Mekong Delta using Radar Imagery. Earth observation Quarterly. European Space Agency, December 1997.
- Huke, Robert E. and Eleanor H. Huke. Rice Area by Type of Culture: South, Southeast and East Asia. Manila: International Rice Research Institute, 1997.
- Morales, Leticia. Warms weather ahead as El Nino returns. Manila chronicle. Manila, 27 July 1997, pp. 10-11.
- Philippine Atmospeheric, Geophysical, Astronomical Services Adminstration. EL NINO Pamphlet. Quezon City: DOST-PAGASA, 1994.
- Reuter. Levels of five major dams dip due to "below-average" rainfall. Business World. Manila, 14 August 1997, p. 16.
- Salita, Domingo C. Geography and Natural Resources of the Philippines. Quezon City: JMC Press, Inc. 1997.
1998 Philippine Yearbook.
