In order to improve the hydrologic cycle in urban catchment with impervious area, 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 increase of spring yield in urban catchment area. We measured water balance in a single RII and urban catchment area in which a small spring, named Kaga-Simizu 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. 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-Simizu Spring increase recently mainly due to installation of RIIs with higher infiltration capacity.
