- The need for water security: based on the city’s current water supply strategies and its population growth, it is projected that by 2025 Semarang’s water demand will exceed its supply. PDAM’s (Local Government Water Enterprises) water distribution is concentrated in the city centre, leaving those living outside to fulfill their needs by building pumped wells, purchasing from water trucks and collecting from distant water springs.
- Climate change risks: Climate change will exacerbate water shortages by broadening the drought impact area, increasing flooding and water contamination. Increased flooding, drought and clean water shortages will likely exacerbate vector-borne disease incidences, potentially presenting
an additional health and economic burden to already poor households. Semarang needs to find alternative inexpensive technologies to address the water scarcity and flood issues.
This project conducted a pre-feasibility study to determine the potential of rainwater-harvesting in reducing climate change vulnerability, particularly flood and drought, in Semarang. A greater understanding of potential for rainwater harvesting allows the city to better manage the anticipated shortfall in the water supply system and enables households to use clean water without exploiting surface and groundwater resources.
Key activities included:
- Data collection and analysis: available methods of rainwater-harvesting; Semarang hydrological, geographical, and socio-economic data; water systems, supply, and demand; and the cost of the relevant technology.
- Pre-feasibility study of rainwater-harvesting models which are suitable for Semarang.
- Feasibility mapping: production of a map and model of the potential area for implementing rainwater- harvesting technology along with its appropriate method. This enables a proposal for the citywide implementation of a rainwater-harvesting system to be developed.
The key recommendations and lessons learned were:
- Individual rainwater harvesting systems are a financial burden for poor people to develop while communal systems are more feasible. A community participation process also promotes a sense of ownership and assures the maintenance of the rainwater harvesting installation.
- The involvement of the private sector helps to boost sustainability. Many private sector participants are seeking further information about the possibility of using such systems at their sites.
- The Environment Agency of Semarang has begun replication of the rain harvesting systems. In 2011, the Environment Agency built an individual model of rainwater harvesting in 10 locations, for both households and official administration offices. In 2012, they have allocated funds to build another
7 individual systems in locations recommended by this study.
The project contributes to building three resilience characteristics. ‘Resourcefulness’ -undertaking the study generates a shared knowledge base among a diverse group of stakeholders, enabling them to identify problems, define practical citywide solutions and mobilize resources to act. ‘Responsiveness’: better understanding of water demand and the potential for rainwater harvesting will increase resilience by allowing the city to better manage the water supply system. ‘Learning’ -the establishment of a city team, including diverse stakeholders, provides an opportunity for interdisciplinary learning from this and future projects.
Around 44% of the population not currently served by municipal water authorities benefits from rainwater- harvesting technology. These populations are particularly vulnerable to disruptions of clean water, contamination in floods, loss of groundwater, and drought.
Urban Climate Change Resilience Action Areas
Water demand & conservation systems