Water Quality Assessment of Santa Cruz River in 2011 and 2022 in the Vicinity of Liliw and Nagcarlan, Laguna, Philippines

Santa Cruz River has significant importance for the economic development of the Philippines and the inhabitants depending on this river for various purposes. It is also one of the 21 major tributary rivers of Laguna de Bay that has a substantial contribution of 15% to the total lake water. This study aims to determine water quality in part of Liliw-Nagcarlan, Laguna of the Santa Cruz River in 2011 and 2022 and to identify the sub-watershed experiencing changes in water quality. There are three sites used for sampling (Talahibing, Bangkuro, and Lapad rivers). Physicochemical and hydrometry were measured in situ. Temperature, pH, and conductivity are within the normal limits. However, dissolved oxygen was generally above the normal limits based on the DENR Water Quality Guidelines. The results showed that the water quality in 2011 and 2022 was projected to change. The number of settlements, recreational activities, and nature park areas increased while the riparian vegetation decreased. The change in land cover will affect the water quality. The result of the assessment for the temperature and conductivity in 2022 was higher compared to 2011. The increase that occurred was influenced by the reduced dissolved oxygen and the pH level, which can cause fish kills and create significant harm to ecosystems. Flowrate was higher from 2022 compared to 2011, since the temperature increased, and the dissolved oxygen levels decreased from this study. Important correlations between the different parameters and the year of the study were proved.