초록
본 연구에서는 1960년대 이후 공업화와 도시화가 급격히 진행되고 있는 일본 하다 노 분지의 하천을 대상으로 유량과 수질의 변화를 조사하여, 수문환경의 변화에 인위적인 요인들이 어떻게 영향을 미치고 있는가를 알아보고자 하였다. 하다노 시는 분지의 풍부한 지하수를 기반으로 공업단지를 유치했으며, 그것을 계기로 급격한 인구증가와 토지이용변화 가 분지를 중심으로 일어났다. 급격한 도시화는 도시용수 부족을 유발했고, 그 대책으로서 새로운 지하수 개발과 다른 수계로부터 다량의 용수를 도입하여 각 하천의 유출특성이 변화 되었다. 그리고 하수 처리능력을 넘는 생활.산업폐수는 각 하천의 수질환경을 악화시키는 주요한 요인이 되고 있다. 각 하천 상.하류간의 유량증가에 대한 상관계수 r은 0.81-0.92이 고, 유량증가에 따른 오염 부하량은 약 3.7-6.9배로 증가하고 있다. 그리고 하수도 보급이 미비한 선정과 공업단지가 입지한 선앙에서 인위적인 유량증가와 수질악화가 현저하고, 인 위적인 영향에 의한 유량.수질의 일 변화도 뚜렷하게 나타나고 있다. 하수 처리지역의 확 대로 하천 수질은 점차적으로 회복되는 경향을 보이고 있지만, 상류에서의 토지이용 변화의 억제와 지하수의 인공유량 등과 같은 분지의 수문학적 특성을 고려한 근본적인 대책을 강구 하지 않는 한 극단적인 지하수 용출량의 저하를 초래해 하천 수문환경은 더욱 악화될 가능 성이 크다.
The Hadano Basin is located at a distance of about 70kms and 60kms from Tokyo and Yokohama and lies in the south-west part of the Kanto region in Japan. The basin area, which correspoends to the catchment of the Kaname River, is about areal size of 60.7$\textrm{km}^2$ and extends about length of 8kms in E-W direction and about width of 5kms in N-S direction (Fig.1). The Hadano basin is filled with thick pile of the alluvum from deposits composed of volcanic materials, mostly came from the Hakone Volcano and overlain by Fuji Volcanic ashes. Fluvial deposits form the good aquifer, therefore water resources of Handano City has been largely depending upon the eroundwater. Urbanization and industrialization of the basin has been rapid in the last thirty years, after activation of "Factory Attraction Policy of Hadano City" in 1956. Growth in population and number of factory due to urbanization changed the land-use pattern of the basin rapidly and increased the water demands. Therefore, Hadano City exploited a new source of water supply, and have introduced the prefectureal waterworks since 1976. On the other hand, the rapid urbanization has brought about the pollution of streams in the basin by domestic sewage and industrial waste water. Diffusion rate of sewerage systems in Hadano City is 38% in 1993. In ordcr to examine the impact of anthropogenic factors on river environments, the author took up the change of land-use and diffusion area of sewerage as parameters, and performed field surveys on water discharge and quality. The survey has been made at upstream and downstream of the main stream regularly per month, to get informati ons about the variation of discharge and water quality aiong the stream and its diurnal fluctuation. Annual variation has been analyzed based the data from Hadano City Office. The results are summarized as follows. 1. Stream discharge has been increasing by urbanization (Fig.3). Water quality (C $l^{-10}$ , N $H^{+}$$_{ 4}$-N, BOD) has been improving gradually after the application of sewerage service, yet water pollution load at the lower station has increased than that at the upper one because of the larger anthropogenic discharge volumes (Fig.4). 2. Corrclation coefficient of discharges between upper and lower was 0.81-0.92. Pollutant loads of the R. Kamame after the confluence with R. Kuzuha grew up by 2.4-3.7 times as compared with its upper reaches, and it increased to 3.7-6.9 times after the confluence with the R. Muro (Fig.5). 3. The changes of water quality along the stream can be divided into two groups (Fig.6a). First: water quality of the R. Kaname and R. Shijuhachisse is becoming worse towards the lower reaches because the water from branches are polluted. Second: water quality are improved in the lower where spring and small branch streams supply clear water, for example R. Mizunashi, R. Muro and R. Kuzuha. 4. Measured discharge at the upper station in the R. Shijuhachisse is 0.153㎥/sec, and about 55% of this is recharged until it reaches to the lower point. The R. Mizunashi has a discharge of 1.155㎥/sec at the upper point, is recharged 0.24㎥/sec until the midstream and groundwater spring 0.2㎥/sec at the lower reaches. R. Kuzuha recharged all the mountain runoff (0.2㎥/sec) at the upper reaches. The R. Muro is supplied by many springs and the estimated discharge of spring was 0.47㎥/sec (Fig.6b). 5. Diurmal variations in discharge and water quality are influenced clearly by domestic and industrial waste waters (Fig.7, 8).ed clearly by domestic and industrial waste waters (Fig.7, 8).