OPTIMIZING WATER PROVISIONING SERVICES OF FOREST PLANTATIONS IN WATER SCARCE AREAS: A COST-BENEFIT ANALYSIS OF REFORESTATION APPROACHES IN MAASIN WATERSHED FOREST RESERVE, ILOILO

Abstract

This study conducted a simplified water balance modelling and cost-benefit analysis to simulate five reforestation approaches to evaluate the conditions of forest plantations in Maasin Watershed and their implication to current and future water security of Metro Iloilo; and, determine the most economical and sustainable reforestation approach to optimise water yield. The study revealed that the 1997 reforestation has been ineffective in restoring the previous state of water provisioning function of Maasin Watershed as water use of monoculture plantations exceeds the precipitations in dry seasons. It found that reforesting a 100-ha Mahogany plantation with native species at intermediate densities will potentially provide an NPV of PHP163,832,368.47 and deliver sustainable yields beyond 25 years. However, it revealed that reforestation could not satisfy alone the growing water consumption demand of Metro Iloilo. Hence, a combination of upstream and downstream efforts is imperative to tackling water scarcity. Moreover, low-density treatment and reduced soil disturbance in harvesting of bamboo plantations may serve as a potential solution to balancing economic and water supply objectives in the watershed. The study also revealed a disjoint in practice between the EO 23 logging moratorium and the goals of 2016 Climate Resilient Forestry Development Master Plan. Wherein, prohibition of logging and selling of timbers from the watershed ultimately discourages the replacement of monoculture plantations and deprive the communities of additional earnings from forest rehabilitation/treatment activities. Lastly, it points to the critical role of water source diversification and water-sensitive urban planning and development to enable a holistic solution to water scarcity in Metro Iloilo.