EVALUATION OF HYDROLOGIC SYSTEMS IN TAKAMATSU AREA AND THE EFFECTS OF WATER TRANSFER THROUGH KAGAWA TRANS-BOUNDARY CHANNEL

本研究旨在了解高松的水文系统和香川跨界水道的影响，重点是地下水。主要研究结果可归纳为以下几点：1。数据库的内容包括地面高程、土地利用、地质、水资源利用、气象等，并利用GIS软件ArcGIS进行数字化处理。其中，高松数字地质信息库是在现有2000多个台站钻孔资料的基础上建立的。每季度监测65个站的无承压地下水和7个站的承压地下水，以阐明地下水位和水质的时空变化。结果表明，无侧限地下水位在夏末最高，冬春季最低，年变化幅度为1 ~ 2 m，等高线多与地面平行。在水质方面，Stiff图和聚类分析表明，地下水水质变化不大，只有少数站点检测到施肥和海水入侵的影响。承压地下水氚分析表明，非承压地下水已渗入承压含水层。通过水平衡分析，量化了香川水道建设前和现在的水文系统。这表明，水道和土地利用变化导致了相当大的变化，地表径流量增加了30mm，河流低流量增加了190mm，污水系统流出量增加了270mm，蒸散量减少了60mm，入渗量减少了150mm，地下水吸收量减少了170mm。利用估算的水文地质参数、地下水开采、初始条件和边界条件，在500m × 500m网格上对承压地下水流动进行了数值模拟。虽然根据四个站点的记录水位计算结果相当不错，但需要进一步改进对允许地下水吸收量的可靠估计。关于水文地质参数和地下水开采率的更详细的资料是非常必要的。少

The present study aimed to understand the hydrologic systems in Takamatsu and the effects of Kagawa trans-boundary water channel with emphasis on groundwater. Main results can be classified and summarized as follows.1. The database was created about ground elevation, land use, geology, water use, meteorology and digitalized using a GIS software, ArcGIS. In particular, the digital geological information database of Takamatsu was established based on existing boring data at more than two thousands stations.2. Unconfined groundwater has been monitored at 65 stations and confined groundwater at 7 stations quarterly to clarify the temporal and spatial variations of the groundwater level and quality. It was confirmed that the unconfined groundwater level shows the highest in late summer and the lowest in winter and spring with annual change of 1-2 m and that the contour lines mostly run parallel to those of ground level. Concerning the water quality, Stiff diagrams and the cluster analysis d … More emonstrated that groundwater quality has shown little change with a few stations where the effects of fertilization and sea water intrusion were detected. Tritium analysis of confined groundwater indicated that unconfined groundwater has penetrated into the confined aquifer.3. Water balance analysis was made to quantify hydrologic systems at present and before the construction of Kagawa water channel. It suggested that the water channel and the land use change have led to considerable changes, i.e., the increase of surface runoff by 30mm, river low flow by 190mm and effluent from sewage system by 270mm and the decrease of evapo-transpiration by 60mm, infiltration into ground by 150mm and the groundwater uptake by 170mm.4. Numerical simulation of confined groundwater flow was performed on 500m x 500m mesh with estimated hydro-geological parameters, groundwater exploitation, initial and boundary conditions. Although the calculations show reasonably well results against recorded water levels at four stations, further improvement is necessary the reliable estimation of allowable groundwater uptake. More detailed information on hydro-geological parameters and groundwater exploitation rates is highly necessary. Less