Water and Sewerage Charges in Scotland

The paper outlines the statutory arrangements governing water and sewerage charges in Scotland, and comments on the factors affecting the levels of charges. Trends in revenue expenditure over the period 1989–90 to 1992–93 are considered in relation to increases in personal community water charge levels, metered water rates, and costs per household. Non-domestic sewerage rates and industrial effluent charges are also discussed. Some comparisons are made with England and Wales and with other countries. The funding arrangements for capital expenditure and their effect on the levels of charges are described, with particular reference to debt levels and rising expenditure to meet UK and EC standards. Factors affecting future charge levels are also identified.     

An Independent Perception of Regulation in Practice

The paper reviews the regulation of water companies in England and Wales since 1989 by reference to the historical regulation of utilities in these countries. It considers how comparative competition, service standards and charging arrangements are developing. Particular mention is made of the debates over rates of return and household metering. The conclusion is that regulation, to be effective and appropriate, must be capable of evolution.     

HYDRAULICS, WATER QUALITY AND VEGETATION CHARACTERISTICS OF GROUNDWATER-FED OPEN DITCHES

A novel peatland management strategy to utilise the high nutrient-retention potential of degenerated peatlands has been implemented in Northern Germany. The effect of raised water levels and extensive land-use management on hydraulic properties, water quality and vegetation characteristics of heavily vegetated and groundwater-fed open ditches, was investigated at the River Elder Valley - a nationally important wetland case study. A better understanding of the effect of vegetation on the temporal flow patterns and the hydraulic retention times is of high scientific interest, especially for improving nutrient standards in lowland rivers. Within-ditch vegetation and other hydraulic obstructions, including accumulated silt and organic debris, increase the hydraulic retention time and lead to an improvement of the water quality along the open ditch. Lower parts of the open ditches were flooded by the River Elder, due to the absence of a mowing scheme during late summer     

ESTIMATING RECHARGE FOR BRITISH AQUIFERS

This paper reviews methods of estimating recharge for a wide variety of aquifers in Britain. A soil moisture balance technique is used with direct representation of relevant soil and crop properties. Recharge contributions due to rainfall, runoff from impervious areas and leaking water mains and sewers are considered. In many field situations low permeability strata, which overlie the main aquifer, modify the timing and magnitude of the actual recharge. Runoff from less permeable strata can become runoff-recharge at the aquifer outcrop. Reference is made to several case studies.     

SOLVING AN URBAN RIVER EROSION PROBLEM ON THE TILMORE BROOK, HAMPSHIRE (UK)

The Tlimore Brook, In Hampshire, typifies the Impact of new housing development that has taken place In phases over the past 20 years or so, on a river corridor. However, the issue is not one of flooding, because the channel itself had been straightened and deepened in historical times and had been adjusted further by down-cutting; thereby forming an over-large channel sufficient to contain flood flows. Perhaps rarely for lowland Britain, the key problem was that of erosion, threatening adjacent properties. This paper describes the nature of the erosion problem and the subsequent geomorphological design to mitigate it. A key unique feature of this project was the extent of backfilling required, over the entire length, to raise the over-deep channel bed. The project was constructed in 2003.     

THE EFFECTS OF IMPROVING SEWAGE SLUDGE DIGESTION

A model was developed and tested to investigate the effects of various parameters on the processing costs of anaerobic digestion. The model was based on empirical data collected from full-scale plants which varied in size from 35,000 to 900,000 population equivalents. (Equivalent to loading rates of 0.5 to 2.7 kg VS/m³/d.) In spite of different operating regimes and conditions of the plants analysed, various relationships were discovered between: sludge quality and volatile solids destruction; sludge quality and biogas yield; and, effluent volatile solids and dewatering. Where correlations existed, these were used to make predictions on operating costs of the digestion and dewatering plant based on sensitivity analysis. The results of the model were used to make recommendations on how to optimise the operation of an anaerobic digestion plant.     

A Large-Scale Grid-Based Hydrological Model of the Severn and Thames Catchments

This paper addresses the issues of scale and appropriate model complexity for large-scale hydrological models. A grid-based hydrological model, which employs the UK Meteorological Office Rainfall and Evaporation Calculation System, is applied to the Severn and Thames catchments using a grid scale of 40 km, and is shown to reproduce the observed mean annual runoff over a 10-year period to within 6% with no prior calibration. The variation in the model performance is strongly correlated with the linearity of the annual rainfall/runoff relationship and a climate index. At the monthly scale, runoff routing becomes significant, and the introduction of a two-parameter routeing algorithm significantly improves the monthly runoff simulations giving efficiencies of 90% and 88% for the Severn and Thames respectively. The results provide guidance to climate modellers looking for efficient and robust land-surface parameterizations, and indicate the potential application of such a modelling scheme to water resource managers.     

Environmental Implications of Treatment of Coastal Sewage Discharges

The environmental implications of implementing the requirement for treatment of coastal sewage prior to discharge, which were put forward in an EC draft Directive on municipal waste-water treatment, are examined. In order to establish the current situation, the results of a national survey of coastal and estuarine sewage discharges are presented. A review of the impact of sewage discharges on the marine environment is presented in conjunction with an assessment of the impact of sewage-treatment processes on the land and in the air. These aspects are integrated into overall conclusions about net environmental impact. Finally, a decision-tree approach to the assignment of priority to additional action required at individual locations is developed.     

A Review of the 1995–96 Drought in the North West

As environmental regulator, the Environment Agency seeks the best balance between essential needs of water supply and the environment, whilst taking into account costs and benefits; nowhere is this balance more focused than in the management of droughts. The drought of 1995–96 was the most severe on record in the North West, and presented a major challenge to both the water company and the Environment Agency in safeguarding essential water supplies and minimizing the risks to the environment.
This paper describes the management of the drought from the Agency's perspective.     

Impacts of Sewers on Groundwater Quality

This paper summarizes the findings of a recent research project on groundwater contamination from leaking sewers, which was completed for the Construction Industry Research and Information Association. Fifty-four incidents were identified in England and Wales from a combined questionnaire survey and literature review. In addition to recorded incidents, the poor quality of many urban groundwaters suggests some effects from leaking sewers. Age is considered to be the most significant characteristic governing leakage from sewers; ground conditions (predominantly aquifer vulnerability) and usage (private versus public ownership) are also important factors relating to the likelihood of groundwater pollution from leaking sewers. Recommended strategies for reducing groundwater contamination include (a) modification of existing criteria for the service performance grading of existing sewers, (b) improved construction of new sewers in appropriate areas, (c) increased groundwater monitoring, and (d) risk assessments for new groundwater sources.