Author(s): Takuya Yasuoka; Yasuo Nihei; Yoshinori Kawabata; Mitsuru Yoshida; Taro Shoji; Hiroshi Uehara; Takashi Yuasa; Hisako Ogura
Keywords: Rainwater infiltration inlet; Water cycle; Spring water; Runoff; Lake Inba-Num
Abstract: To improve the hydrologic cycle in urban catchment areas with impervious surfaces, we examine the infiltration capacity of two types of rainwater infiltration inlet (RII) under actual rainfall conditions and furthermore clarify the effects of the RIIs on the increase of the spring yield in an urban catchment area. We measured water balance in a single RII and urban catchment area in which a small spring, named Kaga-Shimizu Spring, is located and a lot of RIIs were installed. The results indicate that parts of RIIs may maintain large infiltration capacity even under heavy rainfall intensity. The ratio of infiltration to inflow in RIIs is evaluated to be 77.7-91.3%, showing high performance of RIIs as an infiltration measure. Yields in Kaga-Shimizu Spring haved increase recently mainly due to installation of RIIs with higher infiltration capacity.