Fundamental study on the making method of a groundwater pollution vulnerability map using GIS

开发了绘制地下水污染脆弱性图的系统，该图显示了Katsura河流域单位地下水开采量造成地下水恶化的可能性。首先，采用野外调查和数值模拟相结合的方法，研究了胜原河附近浅层地下水退化的机理。结果表明，河水水质恶化的原因可能是由于大量开采地下水而引起的河水补给。这意味着，可以将来自Katsura River的补给量与该地区地下水恶化的可能性进行比较。因此，我们利用公开市场上的各种数值地图数据，通过模拟Katsura河的地下水补给，制作了地下水污染脆弱性图。在制作地图时，自动确定分析区域并将其划分为有限元，自动评估集水区，并根据数值地图数据估算地下水的透过率和开采量。该方法也适用于日本其他地下水资料不足的地区。该程序在Katsura River流域的应用结果表明，仅使用数字地图数据进行模拟是定性有效的，本研究中创建的脆弱性图被认为有助于确定新的工厂选址或环境影响评估。

The system of making a groundwater pollution vulnerability map which showed the possibility of groundwater deterioration caused by a unit volume of groundwater extraction in the Katsura River watershed was developed. First the mechanism of shallow groundwater deterioration near the Katsura River was studied with field investigations and numerical simulations. The results showed that the cause of the deterioration seemed to be the recharge of deteriorated river water induced by the large quantity of groundwater extraction. This meant that the quantity of the recharge from the Katsura River could be compared to the possibility of groundwater deterioration of this area. Therefore, we made the groundwater pollution vulnerability map by simulating the groundwater recharge from the Katsura River using various numerical map data on the open market. For making the map, the analytical region was automatically decided and divided into finite elements, the catchment area was automatically evaluated, and transmissivity and the quantity of groundwater extraction were estimated from the numerical map data. This procedure can be used for the other area in Japan where there is not enough quantity of groundwater data. The results of the application of the procedure to the Katsura River watershed showed that the simulation using only the numerical map data was qualitatively effective and such a vulnerability map as the one created in this study was thought to be useful for deciding a new plant location or environmental impact assessment.