Evaluation Procedures for Diffuse Pollution Measures using GIS with Topological Data Model

为了评估治理农田漫漫性污染的各种对策，在GIS中开发了利用现有高程数据和地理数据制作拓扑数据集的程序。该程序可以利用地理对象的坐标和高程识别河流、排水沟、农业灌溉区、进排水设施和流量、水质观测站等地理对象之间的拓扑空间关系，并制作拓扑数据集用于污染径流模型。利用几种空间精度不同的现有地理数据集，对径流和污染物量的影响进行了评价。利用不同时间间隔的田间径流观测所得的具体污染物系数分析，灌溉季节的污染物估计值会根据观测间隔的不同而高出数倍。

To evaluate various countermeasures for diffuse pollution from irrigation fields, some procedures were developed for making topology dataset from existing elevation data and geographical data in GIS. The procedures could identify the topological spatial relationships between geographical objects including rivers, drainage canals, agricultural irrigation fields, water intake and effluent facilities and observation stations for flow rate and water quality using the coordinate and elevation of the objects, and make topology dataset to use pollution runoff models. Evaluation of influences on runoff volume and pollutant amount were conducted based on the procedures using several type of existing geographical dataset having different spatial accuracy. From the analysis using specific pollutant coefficients made from field runoff observations with different time intervals, estimation of pollutant amount during irrigation season were several times higher according to the observation intervals.