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

为评价灌区面源污染防治措施的优劣，开发了利用GIS中已有的高程数据和地理数据生成拓扑数据集的方法。该方法利用河流、排水渠、农田灌溉、取排水设施、流量、水质观测站等地理对象的坐标和高程信息，识别地理对象之间的拓扑空间关系，并生成拓扑数据集，用于污染径流模型。利用现有的几种具有不同空间精度的地理数据集，对径流量和污染物量的影响进行了评估。通过对不同时段径流观测资料的污染物特征系数分析可知，不同时段的径流观测资料对灌溉期污染物总量的估算值要高出几倍。

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.