This book presents a wavelet based multiscale nonlinear framework for hydrologic forecasting problems. The methodology is proposed for efficient forecasting of complex systems such as hydrologic system which is characterized by multiscale and nonlinear dynamics. The multiscale model is developed by coupling wavelets and second order volterra kernals. The proposed method is applied to various hydrological problems like stream flow forecasting, groundwater level and flood forecasting. Further, one chapter of the book is fully dedicated in discussing the practical issues related to wavelets application in forecasting. Finally, case studies related to non-hydrologic systems are also covered. The students and practitioners in the are of hydrology, environment and water resources will find this book interesting for their academic curricula and research projects.