The Storage Routing Model (SRM) solver is a runoff calculation solver that uses storage routing models. The models had been developed by Dr. Kiyoshi Hoshi, former Director General of the Hokkaido Civil Engineering Institute (the current Civil Engineering Research Institute for Cold Region, Public Works Research Institute) and former Research Director of the Research Institute of the Foundation of Hokkaido River Disaster Prevention Research Center (the current River Center of Hokkaido). The model has been improved to apply to a solver for iRIC by Dr. Makoto Nakatsugawa of Muroran Institute of Technology, Dr. Tomohide Usutani of Japan Weather Association and Terumasa Nishihara of Civil Engineering Research Institute for cold region. The solver consists of two types of storage routing models: a synthetic storage routing model and a two-cascade storage routing model. The solver is equipped with two functions: One can calculate runoff amount from rainfall, while another can optimize parameters of the storage routing model. Using the iRIC GUI, you can calculate the runoff by applying rainfall data (or rainfall and discharge data) to this solver.