Access to reliable and safe water supply remains a privilege not everyone can afford in the Philippines. Climate change and the El Niño phenomenon have dried up water resources across the country and have led to water shortages even in urban areas, most notably Metro Manila. Despite the ongoing dry spell, the country still expects the rainy season to be as wet as ever, and people are turning to rainwater for possible solutions.

Scientists have looked into Rainwater Harvesting (RWH) technology to solve the water problem since it had been proven to aid in flood and disaster mitigation, food and water security, environmental rehabilitation, and climate change adaptation. In 1989, the government enacted the Republic Act No. 6716, which called for the construction of rainwater collectors and water wells in all barangays in the Philippines. The law, however, has not been strictly implemented and there is still a lack of investments in this area.

A study entitled “Harvesting and Managing Rainwater Using Collapsible Rubber Tanks” explored the use of RWH technology, which involves capturing, conveying, storing, and releasing green water—the portion of rainwater that is stored in soil and potentially available for uptake by plants—in situ. The study particularly utilized the Collapsible Rubber Tank (CRTs), a geotextile fabric-made container, due to its flexibility, foldability, and low cost.

Results of the study showed several advantages to the use of collapsible rubber tanks. They are cheaper to buy since rubber tanks with a 500-800 liter capacity range from PhP 3,500-5,000. Hardware tanks with an 800 liter capacity, in comparison, range from PhP 15,000-19,000. With long-term and widespread use, CRT can help delay flooding by reducing surface runoff and pressure on groundwater use. The design showed versatility in supplying water to areas that are hard to reach and heavily affected by typhoons. Its closed design also discouraged the breeding of dengue-carrier mosquitoes.

While the CRT has received positive feedback from cooperators, the study still calls for improvements in the design, particularly with its durability, use of locally available materials, filtration system, water quality assessment, and application. With further research and partnerships, the CRT has a high potential for wider use and commercialization.

The study was headed by Dr. Marisa Sobremisana along with Engr. Antonio Gabino Sobremisana, Mr. Jasper Aliangan, and Mr. Simplicio Veluz. The study was conducted in Barangay La Mesa, Calamba City due to its inconsistent water supply, as well as the people’s use of rainwater as an alternative water source for domestic purposes.

Aside from CRT, other available RWH technology include tanks made of concrete, plastic, stainless steel, ferrocement, and earthen jars. However, these are expensive and difficult to transport. The study also looked into different tank designs—pillow, rectangular pillow, and square type—to determine their suitability and disadvantages within the area of focus.

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