Research on the solute runoff mechanism from basin and the marine ecosystem at the flood event using the hydrology and seawater flow model

探讨了地质特征和土地利用差异对流域向海域的溶质径流机制的影响。为达到这一目的，进行了现场观测和数学模型模拟。在2007年第4号台风降雨过程中，对乌玛亚多河流域(砂岩-泥岩和森林覆盖)和凯贝河流域(花岗岩覆盖，森林、城市和农田共存)进行了水质和水文观测。两个流域的总降雨量均为200 mm。研究结果如下：1)在径流和溶质径流速率上，乌马阿多河流域(地质特征：砂岩-泥岩)高于卡贝河流域(地质特征：花岗岩)。2)在地质特征与流域溶质补给量的关系上，卡贝河流域大于乌马瓦多河流域，例如，硅质补给量增加了1.63倍。二氧化硅的径流负荷变小，卡贝河流域的径流负荷比乌马阿多河流域低46%，由于没有发生影响海水水质的大范围洪水事件，无法对邻近流域的海域进行观测和分析。但人们认为，能够在相同的降雨波形和降雨量条件下，利用数学模型具体分析不同地质特征、不同土地利用的两个流域的溶质径流机制的差异，是一个非常重要的结果。

The influence that geological features and the difference of the land use gave to the solute runoff mechanism from the basin to the sea area was examined. To achieve the purpose, the field observation and the mathematical model simulation were executed. The water quality and hydrological observation were done in the Umayado river basin(covered in sandstone-mudstone, and forest)and the Kabe river basin(covered in granite, and coexistence ground in forest, urban area, and farmland)at the rain event of Typhoon No. 4 in 2007. The total precipitation was 200mm in both of the two basins.The finding is described as follows.1) In the point of the runoff rate and the solute runoff rate, the Umayado river basin (geological features: sandstone-mudstone)is higher than the Kabe river basin (geological features: granite).2) In the relation between the geological features and the amount of the solute supply from the basin, the Kabe river basin is bigger than the Umavado river basin, for instance the amount of the supply of the silica increases by a factor of 1.63) When the land use upgraded, the runoff loading of silica becomes small The runoff loading of Kabe river basin was 46% fewer than that of the Umayado river basin.Because a large-scale flood event that influenced the seawater quality did not occur, the observation and analyze of the sea areas that were adjacent to the basins were not able to be done. However, it is thought that it was a very important result to be able concretely to examine the difference of the solute runoff mechanism of two basins which have the different geological features and land use, using the mathematical model in the condition like the same rainfall wave form and precipitation.