To obtain a processor module by which a dam hydrologic variable in every point of time can be computed with stable precision and in a small delay time by a method wherein a smoothing processing part which computes a computed value by using a weighted moving average method is installed and an output-value selection part which selects an output value is installed.

An interface 31, a storage part 32, a smoothing processing part 33, a hydrologic-quantities computing part 35 and an output-value selection part 35 are installed in a processor module 30. A water level value or the like which is indicated by a water level gage is input and stored in the storage part 32 via the interface 31. While the water level value which is stored in the storage part 32 and a weight are used, a smoothing processing operation using a weighted moving average method is performed by the smoothing processing part 33, and a computed value which is obtained as a result of the smoothing processing operation is stored in the storage part 32. Then, the output-value selection part 35 compares the stored computed value with a preset application limit value so as to select an output value which satisfies a required precision. Thereby, even when waves are generated in a dam reservoir, a dam hydrologic variable can be obtained always with stable precision.