Analysis of Rainwater Harvesting Methods Considering the Impacts of Climate Change

Rainwater harvesting (RWH) has been practiced for a long time but only 4% of the total rainfall amount experienced in the Philippines is utilized. This study then explored on the impacts of climate change and the forecasted rainfall it could generate in a span of 30 years from 2020 – 2050. A local climate model was developed to forecast the annual rainfall for the next 30 years utilizing Representative Concentration Pathway Scenarios 2.6, 4.5, and 8.5. Extracting the minimum and maximum annual rainfall from the projected rainfall, the estimated net runoff was determined which is the study’s sole parameter along with a limited catchment area of 40 – 100 m2 in analyzing a RWH method in Barangay San Jose, Antipolo, Rizal. A range of estimated net runoff through the critical scenario of RCP 8.5 was known to be between 60.042 m3 – 234.409 m3 that could be harvested annually. The study has gathered the most common materials and usual capacities of the set collection devices (i.e. rain barrels/drums, tanks and cisterns) and their possible placements available and manufactured in the Philippines. Through the minimum net runoff, a 55-gallon Polyethylene (P.E) rain barrel/drum is suggested and at most, a 12,000-liter P.E/Stainless tank is suggested for the maximum net runoff. The study recommends that parameters like water demand, economy and reliability factors be taken into consideration for better analysis of appropriate RWH methods to be applied in a specific study area.