|
“GIS in Design and Asset Management of Intermittent Water Distribution Systems”
Suchith Anand MSc Student in GI, City University, London suchithanand@hotmail.com Dr Kalanithy Vairavamoorthy South Bank University,London
Intermittent water distribution systems are water networks that operate at intervals i.e. not continuous. These types of systems are adopted as a common method of controlling water demand, usually by necessity rather than by design. It is a fact that the majority of water supply systems in developing countries are water starved and operate intermittently but the need to rethink the design procedure has received very little attention.
Conventionally the design of water distribution systems has been based on the assumption of continuous supply. In most developing countries water supply is not continuous but intermittent, and this could have been foreseen at the design stage. By trying to fit in a system that was designed to operate as a continuous one to operate intermittently results in severe supply pressure problems in the network and great inequities in the distribution of water. The overall shortage in water availability in most developing countries necessitates intermittent supply at a low per capita supply rate. In particular they often lead to inequitable distribution of available water resources. Since these systems are water starved, consumers collect as much water as possible, quantity collected being directly related to pressure at outlets. And since pressures vary greatly in the network, quantity of water supplied is inequitable. In addition to inequities, low pressures arise because systems are designed based on low per capita allocation and with the assumption that demand is over a 24 hours at about 2.5 times average flow rate. In reality water is drawn in a shorter duration. This implies that the system suddenly becomes undersized because flows in pipes are much greater than anticipated resulting in severe pressure losses. Hence, there is generally a low-pressure regime in the network. In intermittent water networks the quantity of water collected by consumers will be dependent on the driving pressure heads at the outlets and hence the relationship between the pressures in the system and the demands are important, and it cannot be assumed that demand will be met under all conditions. Therefore, the application of standard methods of network analysis to intermittent flow conditions is inappropriate and hence the need for modified design for intermittent water distribution systems. The Design Guidelines formulated by Water Development Research Unit of South Bank University, London under Dr K. Vairavamoorthy is a big step in this direction and my study is based on this. GIS in Design and Asset Management An important component of a water supply system is the distribution network (pipes, nodes, pumps, valves and storage tanks). A water distribution network design involves optimal design of network components and all the raw data needed for analysis and design has spatial component and hence the need for GIS integration. Any water distribution system design involves the analysis of network data in the form of pipe parameters (length, diameter, roughness coefficients etc). This task is voluminous and takes up huge resources in terms of skilled man-hours in trying to build up a framework. Also for optimal network design parameters of the network components are varied and recompilation carried out. This is a mammoth task in itself and by the use of GIS helps the design engineers in not only speeding up the process but also devising better techniques for doing this. Basically there are two types of design. First case is to design for an entirely new system and second one is to augment an existing system. In both case data on network components is of great importance. Proper Techniques for Asset Management is a huge problem faced by engineers in developing countries and GIS holds the key in helping them do this. Also by the use of web based maps of the network, the engineers in the different field offices can by cost-effective means be able to access network information. Once all the network information is stored in a GIS it makes the use of querying possible with ease and helps the planners in better understanding of the system and is able to act in a effective manner to any contingencies that may arise. Use of GIS data though Web based interfaces offers staff in a distributed environment manage the assets in a cost-effective manner. A water distribution network design involves optimal design of network components and all the raw data needed for analysis and design has a spatial component and hence the need for GIS integration. GIS finds its role in the Analysis, Policy, Design and Implementation phases of Intermittent Water Distribution Systems and should be envisaged on this bigger picture. GIS can be used as an integrated tool in processing of spatial data for the overall design and asset management of intermittent water distribution systems.  Figure1: Demand Area with polygon around primary nodes and distribution of the demand
Page 1 of 2
| Next | |