In the years and decades ahead, water and wastewater utilities can take many different actions to reduce greenhouse gas emissions. But what if they don’t? This is not a pessimistic question, but a very important one. Modelling a future with no mitigation actions – business as usual – is an important part of ensuring that actions happen.

That idea is the basis of WaCCliM’s new approach to understanding business-as-usual futures, the Methodology for Establishing Baseline Scenarios in the Urban Water Sector with ECAM.

The approach builds on the Energy Performance and Carbon Emissions Assessment and Monitoring (ECAM) tool, a first-of-its-kind online tool that allows water and wastewater utilities to take a holistic approach to reducing energy use and greenhouse gas emissions throughout the urban water cycle. ECAM allows utilities to enter their existing data into the tool and model actions they are considering to estimate the benefits of mitigation. The new baseline methodology goes a step further by identifying how emissions would evolve over time if current management and practices were to continue.

As water flows through an urban water cycle to meet the needs of residents and industry, greenhouse gases are produced indirectly through energy consumption, and often released directly from untreated or poorly treated wastewater. Modelling the unchecked growth of these emissions allows utilities to reveal the benefits of investing in mitigation – which they can do by getting more energy efficient, stopping water losses, better managing wastewater and sludge, or extracting and using biogas, among other possibilities.

Baseline scenarios are far from simple models; projecting past developments into the future requires many parameters and the best available data. Scenarios are based on the physical and biochemical characteristics of the emission pathways in the urban water cycle, with key parameters affected by socio-economic, technological and climatic forces, ranging from the numbers of people expected to move to cities to the composition of their diets. For rapidly growing cities in countries with developing economies, the only certainty with these parameters is that they will not stay static in the years ahead.

Yet it is possible to project them. They can be based on the trends derived from international and national databases, journal publications, reports and policy documents – including the reports and models of the Intergovernmental Panel on Climate Change (IPCC), which WaCCliM’s methodology takes as a basis.

There are four steps to the methodology. The first step involves defining the boundaries of the specific urban water cycle to be considered, and the time horizon over which it will be modelled. In the second step, the key parameters and driving factors of the emission trajectory are determined, taking national and global trends into account. The third step is data collection and projection, and for this WaCCliM has developed a custom Excel-based tool, Project ECAM Inputs for GHG Emissions (PEIGE). This generates a projection of business-as-usual conditions in future years that, in the fourth step, can be entered into ECAM’s freely available online interface to compare with alternative scenarios.

The power of this methodology is evident in two initial case studies published by WaCCliM. In Madaba, Jordan, WaCCliM modelled the possible trajectory of the utility Miyahuna’s greenhouse gas emissions under business as usual all the way to 2040. These will be critical years, with population growth, economic development and an influx of refugees widening the gap between water supply and demand in the dry region. The scenarios showed that the direct and indirect greenhouse gases emitted by the utility could increase from around 40,000 tons carbon dioxide equivalent (CO2e) in 2016 to nearly 110,000 in 2040, if the utility were to continue with no changes to its operations.

In San Francisco del Rincón in north-central Mexico, unsustainable abstraction, high water losses and inadequate wastewater treatment challenge the two utilities Sistema de Agua Potable y Alcantarillado de San Francisco (SAPAF) and Sistema Intermunicipal para los Servicios de Tratamiento y Disposición de Aguas Residuales para los Municipios del Rincón (SITRATA). WaCCliM also modelled the trajectory of these utilities’ business-as-usual emissions to 2040. The scenarios showed that emissions from the water supply system might increase by up to 58%, while emissions from the wastewater system could dip by 8% thanks to a gradually expanding treatment area.

Neither in Madaba nor in San Francisco del Rincón, however, did business proceed as usual. Among other measures, the Jordanian utility has upgraded pumps to more efficient models, already achieving 1,000 tons CO2e mitigation per year despite its fast-growing service area. The Mexican utilities, instead of expanding wastewater treatment gradually, have acted much faster to extend the system from 48% of the city to 80%, achieving mitigation of 2,500 tons CO2e per year.

The effects of actions like these need to be measured against something – and the business-as-usual scenarios are that something. The methodology is an important step towards estimating the reduction of utilities’ carbon footprints, and a strong technical component for further implementation of climate policies, right up to regional and national scales.