88 The Future of Water in African Cities
Some solutions are available at the household level. Public measures to support household water efficiency include requirements for water saving devices as part of building codes, provision of household water audits, awareness campaigns, and social marketing tools. These strategies are aimed mainly at high- and middle-income households. Building codes can enhance the effect in new estates. The whole potential from water demand management for households in Nairobi in the year 2035 is estimated at about 47,800 cubic meters. One of the features of the IUWM approach is to identify areas or communities that can function as units for development (called clusters). Cluster-level solutions are particularly attractive in new development areas. A number of solutions—for example, in relation to stormwater management, greywater reuse, and leakage management—should be implemented at cluster scale to guarantee the reliability and high quality of the water supply. A cluster can encompass anywhere from a dozen households to estates/new suburbs with up to 50,000 inhabitants. The specific solutions available will depend on the size and sophistication of the cluster, but cluster-level solutions can be more cost effective than the same solutions applied at the household level. For example, in Nairobi, seasonal stormwater harvesting can be enhanced by providing a clusterlevel reservoir that provides storage for three months of supply. Central storage for the whole cluster is more cost effective than if stored by individual households. For a cluster of 10,000 inhabitants with a density of 5,500 persons per square kilometer and a size of 182 hectares (0.182 square kilometers), a storage volume of 82,500 cubic meters must be provided. It is estimated that for the whole of Nairobi, a potential of 111,000 cubic meters per day in the year 2035 at a unit cost of US$0.37 per cubic meter is realistic (Eckart et al., 2012).2 This might be combined with greywater recycling and leakage management at the cluster level. Demonstration pilots can provide the best opportunity to test the opportunities and limits of a new approach. Upon request from Nairobi stakeholders, two locations have been discussed as potential sites for a demonstration pilot. One is Tatu City, planned as a high-income neighborhood; another is Konza Technology City, a 5,000-acre greenfield site at Konza and about 60 kilometers south of Nairobi at the main NairobiMombasa route. In both cases it is proposed that initially the demonstration project should include just one cluster of about 100 to 1,000 inhabitants, and should include stormwater management and greywater reuse. This would test the applicability of IUWM approaches by manag-