The changes in hydrological processes in the Yellow River basin were simulated by using the Community Land Model (CLM, version 3.5), driven by historical climate data observed from 1951 to 2008. A comparison of modeled soil moisture and runoff with limited observations in the basin suggests a general drying trend in simulated soil moisture, runoff, and precipitation-evaporation balance (P-E) in most areas of the Yellow River basin during the observation period. Furthermore, annual soil moisture, runoff, and P-E averaged over the entire basin have declined by 3.3%, 82.2%, and 32.1%, respectively. Significant drying trends in soil moisture appear in the upper and middle reaches of the basin, whereas a significant trend in declining surface runoff and P-E occurred in the middle reaches and the southeastern part of the upper reaches. The overall decreasing water availability is characterized by large spatial and temporal variability.