Water as a climate-change issue
Too much water. High water levels are a common occurrence on the River Ouse as it passes through York.
Building on CIBSE’s success in addressing the carbon issues associated with climate change, the institution’s new president, Professor John Swaffield, argues that water is the new carbon.The causes of climate change encompass more than carbon emissions, and addressing them will require a more holistic approach. CIBSE has by virtue of its history and its constituent membership the ability to operate across the whole spectrum of issues related to climate change. Each member brings separate skills that may be used to mitigate climate change. I propose that we strengthen our already growing capability by actively addressing the water-based causes and effects of climate change, bringing to the treatment of this topic the traditional CIBSE skills of providing design guidance and an enhanced approach to research based knowledge dissemination. This objective could be encapsulated by the phrase: ‘Water is the new carbon’.
CIBSE’s role During this year CIBSE will support both the Department of Communities & Local Government (CLG) and the Department for Environment, Food & Rural Affairs (Defra) in their development of Part G of the Building Regulations. In parallel we will complete the CIBSE Guide G on Public Health Engineering. We will also deliver Knowledge Series publications dealing with water-usage and rainfall issues and design guidance on rainwater services capable of handling the challenges of increased rainfall severity and frequency. In addition we will offer guidance through the Knowledge Series and through specific topic seminars on the prevention of cross contamination in a range of building drainage situations. I urge all CIBSE members to familiarise themselves with these areas; their impact on your work will be significant. Handling the consequences of climate change will require research- led initiatives that will feed our dissemination of subject knowledge and design guidance. This year CIBSE will strengthen its growing links to the research councils and improve its response and involvement capability for both the now reducing ‘responsive mode’ and ‘managed programme’ approaches being followed by the Engineering & Physical Sciences Research Council (EPSRC). CIBSE must continue to improve its performance as a ‘learned society’ and I have longer term proposals that will allow CIBSE to achieve that as well as moving CIBSE into a position where it may become the natural forum for partner groups who share our commitment to improving our built and sustainable environment.
The impact of climate change Climate change will lead to a multiplicity of water-based problems, ranging from the accepted rise in sea levels to increased hurricane frequency and severity and precipitation increases due to rising sea-water temperatures. Along with the probability of increased severity and frequency of rainfall, with consequent flooding, will also come water shortages — with the already evident disparity across the UK being reinforced. These problems will also have political as well as engineering consequences — and CIBSE should not be afraid of having opinions in these areas too. Global political issues as to the absorption of mass population migrations will contrast sharply with the more parochial issues of where to build the increased housing stock the UK will need in the next 50 years and whether realism will predicate major relocation of centres of government and industry. As an engineer, I obviously believe in engineering solutions. In dealing with climate change we have two major advantages. We have the intellectual ability to understand the science of our planet and the innovative ability to transform that scientific understanding into engineering solutions. In our efforts to handle climate change, I therefore believe that we will require more, rather than less, technology to stand beside the renewable ‘green’ agenda. Therefore I would expect ‘big engineering’ in the form of tidal barrages, an enhanced nuclear industry, the development and application of carbon sequestration and a possible national water grid to be solutions we should welcome, possibly providing both climate change modification as well as Rooseveltian economic solutions. Climate change will provide challenges for the building-services engineer as we will be confronted with both too much and too little water, and we will have to develop both a fundamental understanding of the processes involved as well as design strategies to deal with both conditions. More frequent and severe rainfall Current predictions indicate that UK rainfall severity and frequency will increase during the winter months. To avoid surcharging existing sewers we must understand the techniques necessary to attenuate and delay the peak flow discharge from any roof or catchment area within the building boundary — basically an application of the unsteady continuity-of-flow equation where inflow equates to outflow minus the rate of change of storage within the control volume, in this case the building or property boundary. This requires an understanding of the time-dependent nature of rainfall-induced sewer flows.
WCs can now be flushed with less than 5 litres of water, and Australia has achieved a 4/2 litre dual flush.
Solutions will include intervention storage tanks that may or may not be utilised as part of a rainwater harvesting system or so-called green roofs that allow a proportion of the precipitation to be absorbed or re-evaporated to the atmosphere or, indeed, a reversal of the popular urban replacement of front gardens with vehicle parking. Other solutions available to the engineer include siphonic rainwater systems that allow a reduced number of system downpipes to remove rainwater from roofs quickly by running full bore under siphonic conditions. Such systems have been installed successfully at many prestigious buildings, including the Sydney Olympic Stadium, Hong Kong Airport and Murrayfield in Edinburgh. There is a need to translate the research undertaken in this area into useable design guides. Intervention to avoid drain surcharge will be a major constituent in our efforts to prevent localised flooding and is a contributory element in the application of sustainable urban drainage.
Water shortages Water supply and conservation is a truly international issue. Estimates of the population figures without access to reliable and safe drinking water supplies are daunting. UN initiatives have consistently failed to achieve their objectives due to the scale of the problem, lack of resource and motivation and political instability in the areas most in need of support. While access to water in the 1880s may have sparked the Lincoln County Cattle Wars, in the 21st century I think I agree with the Israeli general who, when asked if water could be a cause of conflict replied: ‘It’s cheaper to build a de-salination plant.’ In the UK, along with other developed countries, water shortage is exacerbated by both local shortfalls in precipitation and by our choices as to urban location and life style. Defra proposals indicate a reduction in water usage from 150 l per capita per day to 120 to 130 by 2030. This aspiration has to be seen against a background of climate change that over the same period is expected to result, in the southern UK, in high summer temperatures and dry conditions — while extreme winter precipitation will become a normal event. In the UK, 52% of water is used domestically, of which up to a third is used to flush WCs. In commercial buildings, the equivalent figure, including urinals, approaches 60%. Government will require the input of CIBSE as the relevant engineering institution with access to reliable design methods to assist in setting the targets for water usage. These targets will have to take into consideration both the local water resource and the local housing and commercial/industrial water needs. It may well be that the outcome of such discussions will lead to differential targets nationwide or to decisions as to re-location of population. During 2008 CIBSE will work with DCLG and Defra to deliver the awaited Part G of the Building Regulations that will offer guidance on water usage levels acceptable across the UK. Some approaches to water conservation are predicated on a change in user attitude. However as an engineer, I have a distrust of policies based on changing population attitudes and would rather base water conservation on enhanced product design to yield the same user satisfaction without the user necessarily being aware of the reduction in water use. During the 1970s Scandinavia was regarded as leading the field in efficient appliance design. However, undeniably due to the extended droughts suffered in the past decade, Australian industry has taken on this mantle. Despite WC water usage reducing internationally, a time traveller present in 1900 at the discussions between the Metropolitan Water Board and the appliance manufacturers aimed at reducing flush volume from 40 litres, who then moved forward to London in 1998 to attend meetings of Defra’s Water Regulations Advisory Committee, would have been amused at two things that would not have changed over the hundred years — the speed of travel across the capital and the arguments put forward by the manufacturers to resist reductions in flush volume. Water conservation is a continuing issue that will require CIBSE’s involvement into the foreseeable future and also require an understanding of the possible consequences of such initially attractive schemes as grey water re-use on the system as a whole. For example, whether replacing the quasi-steady discharge from baths — relatively efficient sources of waste transport in the building drainage network — with an equal volume delivered in a series of rapidly attenuating WC flushes remains to be evaluated. This article is based on part of Prof. Swaffield’s CIBSE presidental address ‘Living with the albatross’.
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