The Molawin River, also referred to as the Molawin Creek, is one of the many low volume flowing rocky streams crisscrossing the UPLB and Los Baños area. Molawin Creek crosses the whole of the UPLB campus and essentially cuts it in half making it necessary to construct several bridges throughout the University's history to improve the campus' integrity and general accessibility. Volume of flow depends on the average rainfall of the season and develops into a raging river during typhoons or heavy rainfall. It is a minor tributary of Laguna Lake, one among many small creeks that empty into Laguna de Bay. The origins of Molawin Creek and the other creeks in Los Baños have not been pinpointed but are generally accepted to have their origins high up in Mount Makiling.2.
The study noticed that nutrients (phosphates and nitrogen fractions) were generally high near the Los Baños garbage dump. The presence of these nutrients leads to eutrophication. That area of the river also exhibited the highest biological oxygen demand, indicating high biodegradable organic matter content. Since decaying garbage and domestic wastes from the residents around the area were thrown here, the study, suggested that leachates could have led to these problems.
The Los Baños garbage dump has since been improved and converted into the Los Baños Eco-Waste Management Center, although some controversy regarding the status of the leachate situation have since been raised again.
As in the other tributaries to Laguna de Bay, the Molawin was noted to have low Dissolved Oxygen because of the presence of decaying organic matter, which uses up oxygen.
On its banks stands Baker Hall, the oldest building on the campus, which was used by the Japanese during world war two as the Los Baños Internment Camp, holding civilian prisoners of war. The battle to liberate it is now known as the Raid at Los Baños.