It is also one of 21 major tributaries of Laguna de Bay, and is said to be responsible for up to 35% of the water that flows into the lake. It is thus regularly monitored by the Laguna Lake Development Authority(LLDA) through one of its 15 river monitoring stations.
The river's headwaters drain from the famed Mount Banahaw, and from there cascade down gorges and waterfalls which have made Pagsanjan one of Laguna Province's most popular tourist destinations. For the people who live near it, the Pagsanjan River is an important source of food, water and livelihood.
The waterfalls for which the Pagsanjan river is famous is actually the 300-foot "Magdapio Falls", located in the town of Cavinti. Because the boat ride towards the falls starts in Pagsanjan, however, it is most often referred to as "Pagsanjan Falls". This "boat ride" consists of a 17 kilometer trip in a banca, shooting 16 rapids, and passing through gorges over a hundred feet high, all the while guided by a set of bangkeros positioned at each end of the boat.
The natural environment of the river has been preserved for the tourists who while taking the banca ride "will see wild orchids, ferns, vines, spiders, dragonflies, lizards on the rocks, chattering monkeys and the beautiful sun rays passing through the trees, touching peaceful water and high above are the multi-colored birds flirting in the bushes."
In the latest (December 2005) Water Quality Status Report listed on the Laguna Lake Development Authority's site, the Pagsanjan River was listed as "Class D, with high total coliform concentration."
According to the DENR's Water Usage & Classification for Fresh Water, Class D Quality freshwater is suitable for agriculture, irrigation, livestock watering and industrial water supply class II.
The report also indicated that this status had been "maintained" since the river was last monitored.
The LLDA's conservation efforts for the major tributaries and watersheds of Laguna de Bay have led to the creation of the Laguna de Bay River Basin Councils, of which the Pagsanjan-Lumban River Basin Management &. Development Fdn. is particularly tasked with conservation of the Pagsanjan.