Abstract: The Chinese Loess Plateau is a unique area in the world, dominated by a semiarid climate with unusual land surface hydrology. The previous studies have paid little attention to the nonprecipitation land surface hydrological processes, such as dew formation, on the semiarid Loess Plateau. Therefore, it is important to improve our understanding of the micrometeorological conditions controlling dew formation and the main characteristics of the land surface water balance. Here, we have analysed the observation data on land surface processes, collected at the Dingxi observational station in the LOPEX experimental area, to investigate the relationships between dewfall (or frost) amount and micrometeorological conditions, the characteristics of the seasonal distribution of dewfall (frost) and the influence of precipitation and other weather conditions on dewfall (frost). The fractional contributions of precipitation, dewfall, fog and soiladsorbed water to the land surface water balance are also calculated. The differences between land surface evapotranspiration rates observed by the three methods (eddycovariance, large lysimeter and evaporation pan), and the balance between evapotranspiration and the total land surface water sources are discussed. The land surface water sources, without precipitation or evapotranspiration, jointly constitute a diurnal cycle known as “water respiration” on the land surface. It has been found that the amount of dewfall (frost) is influenced by micrometeorological conditions: a higher relative humidity of the atmosphere surface layer leads to greater dewfall (frost). The amount of dew (frost) is greatest under an inversion strength of 0.25℃ and wind speed of 1.5 m/s, explaining why dewfall totals are the greatest in autumn, secondgreatest in spring and the lowest in summer and winter. Over an annual cycle, the total land surface water sources are similar to evapotranspiration values observed by both the methods of lysimeter and eddy covariance, indicating that the land surface water budget is close to a steady state. In the semiarid region of the Loess Plateau, precipitation is still the dominant water source, but nonprecipitation surface water can account for more than about 15% of the total land surface water sources. Of these nonprecipitation land surface water sources, soil absorbed water is the greatest, followed by dew, and fog is the weakest.