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Risk Mapping of Groundwater Nitrate Nitrogen (NO3-N) Under Intensive Cropping Systems in the Philippines
Carlos M. Pascual
Professor
Mariano Marcos State University,
Philippines
Email: cmpascual123@yahoo.com
The groundwater resources in a 265 ha of highly diversified and intensive rice-based environment was endangered to NO3-N contamination with spatial degree of influence and temporal vulnerability risks as affected by intensive cropping systems with application of high N-fertilizer and judicious use of groundwater for irrigation. Such nitrate contamination levels are above the World Health Organization’s maximum contamination level of 10 ppm for drinking water. Tree-joining, complete cluster analysis of monthly groundwater depths from 1994 to 2002 on observation wells revealed three distinct groups of wells differentiated by groundwater depths. Planting of nitrate catch crops such as legumes to reduce groundwater contamination and vigorous information dissemination on ill-effects of high nitrate-nitrogen (NO3-N), as well as groundwater recharging were considered to reduce NO3-N levels. The combined-use of GIS and GPS proved useful for spatial and temporal risk mapping assessment on groundwater NO3-N vulnerability among other geo-referenced attributes of groundwater at the study site. Such systems analysis tools can be used by planners, researchers, extension workers, students and farmers for other thematic risk mapping, assessment, extrapolation analysis and strategic planning.
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