It is the aim of this book to present the use of computer-aided techniques in hydrologic modeling, with emphasis on the application of computer softwires based on physical and data-based hydrologic models which are publicly available to hydrological data of Malaysia. With the aid of a computer, complex hydrological problems are solved with speed and accuracy. Topics covered in this book include regional flood frequency analysis, regional low flow frequency analysis, flood and drought analysis, forecasting, flow forecasting, unit hydrograph methods in flood estimation, and missing streamflow data infilling using hydro climatological data.