Galvanic Corrosion of Lead Solder in Copper Pipework

The galvanic corrosion potentials of thirty-eight different waters were measured on site, using 'Oliphant' corrosion cells, for lead-tin solder coupled to copper. A wide range in corrosion potential was found, and the chloride-sulphate ratio had the most significant effect on corrosion potential. Tests to reduce corrosion potentials by dosing sulphate, silicate, zinc and orthophosphate were carried out. Zinc dosing, especially in combination with ortho-phosphate, was the most effective treatment for all waters, but posed problems.
Contamination of tapwater by galvanic corrosion of lead solder occurs early in the life of new plumbing, and risk of exposure to contamination can be reduced by flushing before drawing dietetic water. Best-of-all, lead-tin solder should not be used.     

South West Water's 'Clean Sweep' Programme: Some Engineering and Environmental Aspects

The requirements of environmental legislation demand a massive clean-up of coastal discharges for Devon, Cornwall and West Dorset. South West Water Services Limited have developed a marine improvement programme which (a) is the largest of its type in Europe and (b) seeks to address the requirements of legislation incorporating town planning policies together with the increasing public awareness of environmental issues. The pressures around the region's coastline within the foregoing framework set the challenge of achieving the required understanding of coastal processes, together with the implementation of engineering solutions to meet with society's expectations. These have to be achieved at least cost and provide the most innovative and effective engineering solutions for the efficient implementation and management of such a programme.     

Flood Generation Modelling

This paper summarizes recent research and development of a particular process-based runoff generation model, the Institute of Hydrology Distributed Model. Surface and subsurface flow equations are linked in a hydrologically appropriate system to allow simulation of catchment runoff processes. Predictions can be made of channel flow, surface runoff and subsurface flow, pressure potentials and water contents. The structure and methods of the model are described and its data and computing requirements are outlined. Field and systematic applications are discussed, together with the work carried out on providing guidelines for use for the wider hydrological community.     

Middleton-in-Teesdale Supply Area: Improvements to the Supply Network

The paper covers the design of improvements to a water distribution system serving a rural area to eliminate low chlorine residuals and to cater for large potential increases in demand from an agricultural estate. A model of the existing system was analysed at current and increased demands to identify weaknesses in the system. The model was altered by the addition of pumping mains, two storage reservoirs at new locations, and the strengthening of distribution mains to provide a solution to meet the client's requirements.
The location and size of the proposed reservoirs were optimized with respect to the construction costs of the reservoirs, pumping and distribution pipelines, and pump running costs.
Areas were zoned to provide better strategic storage, whilst also reducing retention times, thus eliminating the problems of low chlorine residuals.     

Practical Aspects of Yield Investigations of Groundwater Sources

Lee Valley Water plc has, in a joint study with the University of Birmingham, been reassessing the reliable yields of its existing chalk sources in order to make maximum use of the available groundwater resources. An approach to yield assessment was developed which took into account the hydrogeology and flow processes in the vicinity of pumping stations, and within the contributing area. The yield of many sources was found to be very dependent on regional water level conditions. Initial estimates of potential yields were made but future monitoring should aim to clarify the interrelationship between source output and aquifer state.     

Reservoir Sedimentation and Colour Problems in Southern Pennine Reservoirs

A study of two major environmental issues in upland water management is presented. Discolouration and reservoir sedimentation are seen to affect water managers on different timescales and to different degrees. Rates of reservoir sedimentation, adjusted for empirically derived trap efficiency, are measured and found to be higher than previously believed. A link between sediments found within the reservoir basin and the generation of colour is described.     

The Effect of Leakage Control and Domestic Metering on Water Consumption in the Isle of Wight

The paper presents a brief background to the national metering trial on the Isle of Wight, for which installation was completed in early 1991. Various aspects of the meter installation policy are relevant in terms of their effect on leakage. The main part of the paper describes some early indications of the impact of domestic metering on leakage and consumption in the Isle of Wight Division of Southern Water Services Ltd.     

The Impact of Measurement Uncertainty on the Water Balance

The 'water-balance calculation'is a valuable method of assessing the integrity of many components of a company's distribution system and is used in (a) evaluating the overall performance of the system and (b) assessing, for example, leakage within distribution zones or district metered areas. However, the quality of data which are derived from balance calculations reflects the quality of the input data, and each input source (whether metered or estimated) is subject to uncertainty.
This paper explores the impact of input uncertainty on the water-balance calculation, and uses Anglian Water's annual balance as an example. The principal contributors to overall uncertainty are identified, and these show that the overall uncertainty depends upon only a few of the many inputs. Identifying these critical inputs has enabled Anglian Water staff to target the areas of their auditing chains that will yield greatest benefit to the reporting process.     

An Evaluation of Some Methods of Determining Storage Yield Relationships for Impounding Reservoirs

Twelve methods of storage yield estimation available in the hydrological literature are identified. Eight of these are then selected for use in a comparative study where the objective is to select those methods with least bias and standard error. A time-series model is used to generate a population of 3000 years of synthetic flow data for one set of Irish conditions. The true population storage volume for each level of yield and return period is obtained by counting, and the storage estimates obtained using the eight selected methods are compared with the population volume on the basis of bias and standard error. The Modified Gould and Behaviour Analysis Methods were found to have least bias and the lowest standard error. These methods are therefore recommended for use, in conjunction with simulation methods of investigating storage requirements, for Irish and similar climatic conditions.