This text covers entropy-based techniques for parameter estimation in hydrology. The techniques are presented for 20 distributions used in hydrology, including the distributions of the normal family, the extreme-value family, the Pareto family, and the logistic family. A comparative assessment of the entropy-based techniques is made with traditional methods of parameter estimation, such as the methods of moments, maximum likelihood estimation, probability-weighted moments, L-moments, and least squares, using field data as well as Monte Carlo simulation experiments.