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C3.3 Improved efficiency of supply Characteristics Efficiency in the supply and delivery of water includes efficient use of the resource, as well as efficiencies in canal and pipe distribution networks. Efficiency of supply can take place on many levels. Rainwater harvesting is an approach whereby rain is collected and stored in the soil profile, or in tanks, ponds, or cisterns, providing water for irrigation or domestic purposes, rather than immediate evaporation. Rainwater harvesting is particularly useful where rainfall is highly seasonal and can reduce the volume lost to the community in run-off. It has applications in both rural and urban areas where rainfall can be collected from roofs and hard surfaces. At the level of water utility, efficient supply management may involve improvements in: abstraction, treatment, bulk transfers, local distribution, consumer meters, revenue collection, appropriate economic analysis and accounting procedures. Important tools for improving water supply efficiency for utilities include:
Dual supply systems of different water quality for different uses can be a cost effective option (and may be useful for recycling and reuse, C3.2). In irrigated agriculture, where there are often heavy water losses (up to 50%) before the water reaches users, there is much scope for improvement. Improvements in conveyance and distribution and field application can be used to change traditional open canal systems to pipe conveyance and sprinkler/drip irrigation. A balance needs to be struck between the capital investment needed to expand supply capacity and investment in operations and maintenance, and the cost of rehabilitation to make the most efficient use of existing resources and facilities. Water savings will often postpone major capital investments in supply infrastructure (see also A3.5 on investment appraisal). Introduction of efficient supply approaches in utilities or irrigation systems may need retraining and institutional reform. (See B1.6, targets and incentive structures for public service providers, including the need for better paid and trained staff, B2.2 increasing IWRM capacity and training of water professionals). Changes may also need investment in the distribution systems (subject to economic and financial appraisal). See other sections: financing and incentive structures (A3), role of service providers in IWRM (B1.9), institutional capacity building (B2), consensus building (C5.3), regulations for water quality (C6.1), information and communications (C8), and information for awareness raising (C4.3). Lessons learned
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