Abstract: With the end of first nation water census, massive water census data have been generated. To use the cloud computing technology in the area of water census data mining can provide scientific, reasonable supports for the decision of water conservancy in a quick, efficient and economical way. This paper proposes water census data decision tree classified mining algorithm MRC4.5 based on Map/Reduce and water census data of groundwater wells is applied to data mining with the algorithm. The experimental results indicate that compared with the traditional algorithm C4.5, MRC4.5 algorithm has higher efficiency and good speedup when dealing with massive data sets execution.

Key words: water census, data mining, decision-making tree, C4.5 algorithm, Map/Reduce