Regional ecological risk assessment of multi-sources

Regional ecological risk assessment (ERA) is more complex than general ERA, as it requires that risk receptors, risk sources, risk exposure, uncertainty and especially spatial heterogeneity all be taken into account. Taking the catchment area along the Weihe River in Shaanxi Province as a study area, a mathematical model of regional ERA was developed and tested on the basis of elementary principles and methods of risk measurement. Through selecting four main risk sources of drought, flood, pollution and soil erosion, with the assistance of geographical information system(GIS) technique, the integrated risk value which was calculated by indices and formulas was classified into five grades (the lowest, lower, moderate, higher and the highest). Each risk area was assigned to one of the five classes. The results can provide quantitatively theoretic basis and data support for environmental management and ecological risk decision-making in the lower Weihe River.