Review of 'The Impacts of Covid-19 Pandemic and Weather Conditions on Water Environment, a Case Study in Istanbul and London/South-east England'

The authors present a paper, in which they examined how unexpected situations such as the Covid-19 pandemic might affect water usage and availability. Although the paper is well-written and well-structured, I do have some concerns about the paper, which merit further attention.

My first comment relates to the usage of the DPSIR framework. I agree with authors that the application of the DPSIR framework for signaling differences in water consumption patterns during the pandemic. Since climate change and covid-19 are two different drivers (van der Voorn et al, 2020) which manifest themselves at different time scales, including their impacts, there lies a major challenge in obtaining some separate evidence that the pandemic restrictions affected human activity in Istanbul for which they examined air quality parameters, and these suggest air pollution in Istanbul was lower in 2020 than in 2019 indicating decreased human activity consistent with Covid-19 restrictions. However, in order to distinguish between the impacts of these two drivers, I believe the current set of indicators is not sufficient and therefore, I have two suggestions for improvement:

• In order to provide more evidence on “waste”, the authors could consider Wastewater-Based Epidemiology, which could be especially informative given that asymptomatic and oligosymptomatic infections are unlikely to be detected during clinical surveillance  see e.g., Bivins et al (2020) and Bhattacharya et al (2021)
• Since people were in lockdown, they may have ordered products and services online. This would increase (slightly) traffic patterns and at least demand for transportation, which in turn increase CO2 emissions.

In addition, looking at the different time scales to be considered, the DPSIR framework depicted in Figure 1 seems to be a static representation of its DPSIR components. So, in light of the research objective, a more dynamic representation would be required to capture the dynamics across different time scales.

My second concern relates to the comparability of the Turkish case with other cases. In my opinion, there are indeed limited comparisons possible, if not impossible between Istanbul and other countries at present due to lack of data availability, as the authors stated. However, it is not just because of a lack of data but also different national characteristics in terms of socio-ecological, socio-economic, socio-technical, and governance aspects. Hence, it requires a solid framework for comparison, which accounts for these differences and similarities, to make any statements on comparability. These aspects could be interpreted as coping capacities. Van der Voorn and de Jong et al (2021) developed a framework for such a comparative analysis.

My final concern relates to the need for new management plans. This would require adaptive management methodologies like for example the Backcasting Adaptive Management methodology (van der Voorn et al, 2012, 2017) or a comprehensive multi-target backcasting approach (van der Voorn et al 2020), which combines the strengths of multicriteria analysis, nexus approaches and backcasting, for supporting a transition to zero GHG emissions The former methodology can help decision makers to develop robust adaptive management plans, whereas the latter allows them to conduct a qualitative environmental assessment of scenarios to identify conflicts and synergies in regard to a broad range of environmental targets (e.g., reduction of biodiversity loss, viable habitats for flora and fauna). I would like to encourage the authors to elaborate on how these methodologies could expand the DPSIR framework in light of the research objective of the paper.

Recommended literature

Bhattacharya, P., Kumar, M., Islam, M.T. et al. Prevalence of SARS-CoV-2 in Communities Through Wastewater Surveillance—a Potential Approach for Estimation of Disease Burden. Curr Pollution Rep 7, 160–166 (2021). https://doi.org/10.1007/s40726-021-00178-4

van der Voorn, T.; de Jong, M. Cope or Perish? Managing Tipping Points in Developing Coping Strategies for Emergency Response during the First Wave of the COVID-19 Outbreak in Europe. COVID 2021, 1, 39-70. https://doi.org/10.3390/covid1010005

Bivins A, North D, Ahmad A, Ahmed W, Alm E, Been F, et al. Wastewater-based epidemiology: global collaborative to maximize contributions in the fight against COVID-19. Environ Sci Technol. 2020;54(13):7754–7. https://doi.org/10.1021/acs.est.0c02388

Tom van der Voorn, Caroline van den Berg, Prosun Bhattacharya, Jaco Quist. Never Waste a Crisis: Drawing First Lessons from the COVID-19 Pandemic to Tackle the Water Crisis. ACS ES&T Water 2021, 1 (1) , 8-10. https://doi.org/10.1021/acsestwater.0c00041

Van der Voorn, T., Quist, J., Pahl-Wostl, C. et al. Envisioning robust climate change adaptation futures for coastal regions: a comparative evaluation of cases in three continents. Mitig Adapt Strateg Glob Change 22, 519–546 (2017). https://doi.org/10.1007/s11027-015-9686-4

Tom van der Voorn, Claudia Pahl-Wostl, Jaco Quist, (2012) Combining backcasting and adaptive management for climate adaptation in coastal regions: A methodology and a South African case study,

Futures, https://doi.org/10.1016/j.futures.2011.11.003 .