Several rivers and streams cut across the broad plain of Pinamalayan. The major river that traverses the municipality is the Pula River. The Pula River is categorized as Class C by the Department of Environment and Natural Resources (DENR). The beneficial use of Class C is for recreational and industrial uses as well as for the propagation and growth of fish and other aquatic resources.
The other river systems in Pinamalayan are Macanlig, Babahurin, Pinamalayan, Sabang, Buli, and Quinabigan River. Creeks, on the other hand, include Banilad, Pili, Puting-Tubig, Macanlig, Matood-tood and Papandayan.
The type of rocks lain beneath the municipality is alluvium, known for good water bearing abilities. As such, the municipality possesses fair to good groundwater resources. Potential areas of high yielding wells can be found in Barangays Zone I to IV, Cacawan, Sta. Rita, etc.