Hydrological, Ecological and Land Use Dynamics of Watersheds in the Ilocos Region, Northern Philippines

Abstract

Watersheds are essential ecological and hydrological systems that provide freshwater resources, regulate floods, sustain biodiversity, and support agricultural livelihoods in the Philippines. In the Ilocos Region of Northern Philippines, watershed systems are particularly significant due to the region’s upland landscapes and strong exposure to monsoonal rainfall and tropical cyclones, which drive hydrological variability and influence ecosystem stability. However, increasing land-use change including deforestation, agricultural expansion, and settlement development together with climate variability is placing growing pressure on these watershed ecosystems. This mini-review synthesizes literature on the hydrological, ecological, and land-use dynamics of watersheds in the Ilocos Region using a structured narrative synthesis of peer-reviewed literature, government reports, and regional studies retrieved from major academic databases. Findings consistently indicate that forest loss and land conversion increase surface runoff, reduce infiltration, accelerate soil erosion, and degrade water quality. These changes disrupt freshwater ecosystems, weaken ecosystem services, and heighten risks of flooding and seasonal water scarcity for surrounding communities. Although management approaches such as community-based forest management and integrated watershed management have been introduced, effectiveness is often constrained by institutional fragmentation, insufficient long-term monitoring, and weak integration between research and policy. Key research gaps include limited long-term hydrological datasets, insufficient integration of biodiversity indicators in watershed assessments, and a lack of basin-scale analyses linking land-use change to hydrological and ecological processes. Addressing these gaps and strengthening collaboration among scientists, policymakers, and local stakeholders will be critical for advancing sustainable and climate-resilient watershed management in the Ilocos Region and similar tropical landscapes.