T The exisisting precipitation measurement station owned by PT Adaro Indonesia as much as 4 stations, while the area of water flow in the entire mining site is 14.834 ha. Untill today, the number of rainfall station still not enough for the entire area, so the purpose of this research is to count the number of the rainfall station and the additional rainfall station placement pattern. This research is using kagan – rodda method by knowing rain correlation in an observation point wih other points. From the obtained precipitation data, the data processed to determine discharge in sump RL –120, to know amaount of slurry entering the box pit south tutupan area. Because the incoming main water is denied from sump and streamed using help pump. The velocity of the deposition obtained by using stokes law. Based on the results of the calculation as many as 4 rainfall stations produce percent of error alignment 9,56 % and error interpolate 12,12 %. Meanwhile, the additional rainfall stations are 10 pieces, obtaining percent of alignment error of 4,9 % and interpolate error of 11,4 % with the distance between the points are 3,48 km . The maximum prepicitation in the south tutupan are is 6,94 mm / hours obtaining discharge in sump of 3,97 m³/second . With that amount of discharge , The exisisting one of box control exsisting dimensions still enough to accommodate water runoff. Keywords : exsisting, a method of kagan-rodda, stokes law, error alignment, error interpolation, box control