Hong Kong Housing Authority and Housing Department

Approximately 30% of the Hong Kong population reside in public rental housing estates. The HA strives to provide affordable, quality housing through a proactive and caring approach, and to make effective use of public resources. Since 2010, the HA has introduced various greening initatives in different public housing projects as well as studies that cover major areas such as green roof, slope greening and vertical greening.

From 2012 onwards, we have extended our focus on environmental sustainability to water conservation for landscape irrigation, covering root zone irrigation system and ZIPS. It is the first time for the HA to adopt ZIPS as a sub-soil irrigation method to achieve "zero irrigation", that is zero portable water consumption for planting. ZIPS has two major objectives: to minimise the water consumption for greening requirements, and to provide a sustainable urban drainage system. The system comprises a wicking bed mechanism, a self-sustained and passive design to deliver water to the vegetation and to minimise topsoil evaporation through capillary action.

A trial project has been introduced in Lung Yat Estate, Tuen Mun, since November 2013 for a period of 12 months. The water consumption and rainfall records show that the performance of the system is satisfactory during both wet and dry seasons. No manual watering operation and portable water are required. No flooding under black rainstorm warnings is observed and no odour is detected.

The results of our studies are encouraging. Our utimate goal is to share the knowledge for the benefit of the society so as to build a sustaniable green infrastructure, improve living enviroment, enhance human comfort and contribute to proper management of natural resources. The study only serves as a starting point; further development on ZIPS, such as design of ZIPS with tree planting, has been carried out. Detailed design with targets of prefabrication and modular units to simplify the construction is being explored.