The main source of the San Cristobal River is Mount Sungay, the highest mountain of Cavite province, where the main stem and its tributaries drain the northern and eastern side of the mountain. Its watershed area covers Calamba City and Cabuyao City in Laguna, Tagaytay City and the municipality of Silang in Cavite. The river system of San Cristobal from Mount Sungay, is connected to the Matang Tubig located in Casile and Canlubang.