The period witnessed a shift toward uncertainty-aware methodologies in water resources, emphasizing probabilistic framing of hydrologic data and system performance. Two- and three-dimensional groundwater analyses expanded with Monte Carlo methods, treating hydraulic conductivity as a spatial random field to relate aquifer heterogeneity to heads and drawdown, thereby underpinning risk-informed design and management. Multiobjective optimization in river basin development and decomposition-based stochastic programming for reservoir operations emerged as formal frameworks that integrate multiple objectives and uncertainty into decision making. Nonparametric trend tests for water quality were introduced, offering distribution-free tools robust to censoring and seasonality and strengthening long-term environmental monitoring.