The invention relates to the technical field of hydrogeological survey, and is to provide an underground water monitoring device and method for preventing underground water cross
contamination. The device comprises a monitoring
pipe and a
water seepage port. The monitoring
pipe comprises a water taking part and a
water stop part; cavities are formed in the water taking part at intervals along theheight direction of the monitoring
pipe; the
water stop part is annular and wraps and is fixed to the side face of the water taking part; horizontal screw rods are rotationally connected to the positions, corresponding to the upper ends of the cavities, of the two sides of the water taking part; each screw rod is in threaded connection with a stop block, and the screw rod and the stop block are located in the
water stop part; outlets allowing the stop blocks to penetrate out are formed in the positions, right opposite to the stop blocks, of the side face of the water stop part; and before monitoring, the monitoring pipe is located in the
drill hole, and when the stop block slides to the end, away from the water taking part, of the corresponding screw rod, the stop block is exposed out of the outlet and extrudes the
drill hole. The method has the advantages that cross
contamination of underground water is reduced, and meanwhile, stratified
water pumping and sampling are conducted on theaquifers of different depth sections in the drilled holes with the same hole
diameter.