Description of the application

Helsingborg (pop. 123,000), on the south coast of Sweden, is a city undergoing change and is expected to grow over the next few decades. This presents a problem for municipal water managers as the combined sewer system and waste water treatment plant in the central city are already prone to problems such as combined sewer overflows (CSO) and pumping station overflows of untreated waste water to local receiving waters following heavy rainfall. Continued urbanisation could put even more stress on the system leading to further failure. In this study, the potential impacts of climate change and continued urbanisation on waste and stormwater flows in the combined sewer of central Helsingborg, South Sweden, have been assessed using a series of DHI MOUSE simulations run with present conditions as well as two climate change scenarios and three progressive urbanisation storylines. Sewer flows resulting from different urbanisation storylines were simulated for two 10-year periods corresponding to present (1994–2003) and future climates (nominally 2081–2090). In all, 12 simulations were made. Climate change was simulated by altering a high-resolution rainfall record according to the climate-change signal derived from a regional climate model. Urbanisation was simulated by altering model parameters to reflect current trends in demographics and water management. It was found that city growth and projected increases in precipitation, both together and alone, are set to worsen the current drainage problems.

Lessons learned

Without further city development, climate change projected for Helsingborg could exacerbate the current drainage problems (i.e., overflows from the combined sewer) by increasing precipitation and therefore surface runoff.

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Last modified: Sept. 12, 2016, 7:38 a.m.