Comprehensive analysis for water environment in Lake Teganuma with field measurements, numerical computations and GIS.

为实现日本著名富营养化湖泊之一的手鹿沼湖流域尺度的水质综合管理，采用野外实测、数值计算和GIS技术，对手鹿沼湖的水环境进行了综合分析。主要成果如下：1）开发了几种新的污染物负荷监测方法。2）为明确城市区域污染负荷，采用MOS（Modeled-Stormwater Sampling）技术对城市道路和屋顶非点源进行了现场监测。观测结果给出了道路和屋顶沉积物负荷的非恒定过程与干沉降和交通量等主要污染源之间的关系（声学多普勒流速剖面仪）和用于浊度和叶绿素a的光学传感器进行了讨论，4）通过现场测量和室内实验研究了Teganuma湖底泥营养盐释放和悬浮物释放。研究结果表明，营养盐的释放量约占总污染负荷的30-50%。5）提出了一种新的简化的河流水平面坐标系--水平sigma坐标系。此外，为了在准确评价污染物负荷的同时进行湖泊水环境计算，在河流-水流模型中引入水平sigma坐标，建立了河湖耦合模型。

To realize an integrated management for water quality on the basin scale of Lake Teganuma which is one of famous eutrophied lakes in Japan, the comprehensive analysis for water environments in Lake Teganuma were conducted with field measurements, numerical computations and GIS. Main results of the project are expressed in the followings :1)Several monitoring methods to measure pollutant loads were newly developed. These monitoring methods were used to conduct accurate and simplified measurements for road-deposit environments and pick-up and deposition rates of sediments in rivers.2)To clarify the pollutant loads in urban area, the field measurements for the non-point sources on roads and roofs were done with a MOS (Modeled-stormwater sampling) technique presented in this project. The observed results gave the relationship between the unsteady processes of road- and roof-deposit loads and main sources like dry fallout and traffic volume.3)To measure accurately pollutant loads in rivers, the measuring methods with an ADCP (Acoustic Doppler current profiler) and an optical sensor for turbidity and Chlorophyll-a were discussed through the various field tests in the Oohori River, one of main influent rivers into Lake Teganuma.4)Nutrient releases from the bottom and suspended solids in the lake were examined in the field measurements and laboratory experiments. These results indicate that the nutrient release in the lake was 30-50% of total pollutant loads.5)A new simplified horizontal coordinate for computations of river flow, named a horizontal sigma coordinate, was presented. Furthermore, to perform a computation of water environments in lake with accurately evaluating pollutant loads, a coupled river-lake model was also developted by introducing a horizontal sigma coordinate into the river-flow model.