Estimating Sediment Export and Retention Capacity of Existing Land Cover in Balanac and Sta. Cruz Watersheds, Philippines Using InVEST-SDR Model

Abstract

Identifying priority areas for conservation remains a challenge since ecosystem-based models are typically data extensive. As a response to this challenge, InVEST (Integrated Valuation of Ecosystem Services and Tradeoffs) was developed to map diverse types of ecosystem services (ES). Although InVEST has been widely used in other countries, its application within the Philippines has been limited. This study offers an application of InVEST in the Philippine context. We estimated the amount of sediments exported to the streams and retained in the area by land cover type within the Balanac and Sta. Cruz watersheds. Results showed that in terms of best ecosystem service provision per hectare, vegetated areas – particularly forest land – provide the most sediment retention capacity and the least sediment export. On the other hand, the non-vegetated areas – particularly the built-up areas – provide the least sediment retention capacity and the most sediment export. These results suggest that major strategic water quality management and ES changes should be considered when converting land from one land cover type to another. Furthermore, a considerable opportunity for ecosystem service improvement to water quality through soil conservation and sustainable farming practices can be implemented in cropland areas. Since the majority of the land in both watersheds are cropland, its contribution in sediment transfers is significant, hence its role to managing soil health is of utmost importance. The findings of this study could contribute to the advancement of ES modeling in the Philippines to support land development planning and policy decisions at the national and local levels.