The puzzle of the dielectric relaxation in water is still actual and the subject of the intensive studies today. Nowadays, the experimental data of the water dielectric spectra are well known in an extremely broad frequency band. In this work, we develop the idea that the dielectric relaxation in water is driven by the migration of defects of the H-bond network. The normal diffusion of defect leads to the Debye type behavior for the main relaxation peak. These fluctuations are significant at high frequencies and lead to the non-Debye behavior. The temperature dependence of the static dielectric permittivity is explained as well.

Based on the idea of the defects migration as the principle mechanism of the dielectric relaxation in ice Ih, the explanation of the low-temperature dynamic crossover was proposed. Introducing the coupling between the Bjerrum and ionic defects, one can possible to describe the smooth bend of the relaxation time at low temperatures in ice. At high temperatures, the diffusion of the Bjerrum and ionic defects is high and their movement may be considered as independent one. The simple switching between these two mechanisms leads to dynamical crossover at ~235K. However, at low temperatures because of slowing down of the mobility of Bjerrum orientation defects, they may create the blockage for proton hopping. The trapping of the ionic defects by the L-D defects for a long period of time, leads to an increase in the relaxation time and originates the low-temperature crossover.