key: cord-0851581-erl8jftp
authors: Hallema, Dennis W.; Robinne, François-Nicolas; McNulty, Steven G.
title: Pandemic spotlight on urban water quality
date: 2020-05-06
journal: Ecol Process
DOI: 10.1186/s13717-020-00231-y
sha: 6eba6d0bdc1afdde4a6d25fd9acd192d1bc9d18c
doc_id: 851581
cord_uid: erl8jftp

Surface water improvements associated with the COVID-19 economic slowdown illustrate environmental resiliency and societal control over urban water quality.

available, we can also expect to see examples of temporarily improved surface water quality in urban areas. The nature and extent of these improvements will depend on the level of urbanization (regional and distribution within the watershed), climate (predominant wind direction and precipitation), and physical characteristics of the watershed (topography and infiltration dynamics of the soil). The respective contributions of groundwater and storm drainage to river flow can indicate how reduced input of contaminants affects surface water quality. Because upstream portions of watersheds often have a lower level of human disturbance, this is where large basins tend to exhibit a higher level of resilience (Hallema et al. 2019) .

Under an economic slowdown scenario, headwaters hundreds of kilometers away from urban areas will experience reduced deposition from nonpoint sources of pollution (regionally produced nitrogen dioxide, sulfur dioxide, ammonia, and other gaseous pollutants). For example, given the reduction in nitrogen dioxide concentrations observed over Eastern China, Europe, the Northeastern United States, and India ( Fig. 1) , this is where urban surface water quality may start showing signs of temporary recovery. Downstream surface waters may also receive less input from both point sources of pollution (e.g., industrial sites) and nonpoint sources (e.g., motorized traffic), as the lockdowns continue. Under an economic worst-case scenario, input from other major nonpoint sources, like mining and agriculture, can potentially decline due to ripple effects created by a slowdown of the global economy. The effects of reduced point source inputs on surface water quality might become evident within a matter of months while the effect of reduced nonpoint source inputs could take much longer to measure.

Given the frequent occurrence of urban water crises, it is critical to document how COVID-19 pandemic response management affects natural processes and surface water quality in the short term. It is equally important to determine how we can better optimize the natural function of water supply areas ) once economic recovery is underway. The current challenge, though, is that economic sectors and industries that contribute to pollution (e.g., energy, consumer, pharmaceutical, and other industries) receive little incentive to promote urban water quality beyond what the law requires. They are chiefly evaluated in terms of total returns to the shareholders; however, an important collateral benefit of economic performance is the creation of jobs and public wealth (i.e., taxation revenue). To improve the sustainability of water supplies and cover the associated cost, it will be necessary for the public, by way of governance, to improve laws and direct public wealth toward outcomes that simultaneously support environmental and economic goals (Claassen et al. 2018 ).

There are very few positive aspects to be derived from the current public health emergency. The environmental responses to the economic slowdown emphasize in the first place the negative effect of humans on their environment. However, they are also a reminder that society has the ability to improve urban water quality in normal times, provided we make a conscious decision and concerted effort to create the conditions needed to reach that goal. 

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