You are here:
Tracking flows of water through a complex urban system: Chicago
Citation:
Erban, L., S. Balogh, H. Walker, AND Dan Campbell. Tracking flows of water through a complex urban system: Chicago. Sixth Interagency Conference on Research in the Watersheds, Shepherdstown, West Virginia, July 23 - 26, 2018.
Impact/Purpose:
Like many urban areas in the US, greater Chicago has a complex water system and a variety of related challenges to manage. Flooding and sewer overflows create hazards of excess while contamination by effluents and aquifer overdraft create scarcity, among other issues that vary in significance throughout the region. The regional planning authority, the Chicago Metropolitan Agency for Planning (CMAP), serves seven counties in northeast Illinois on a wide range of topics including water. Planning around water at this scale is limited by data gaps and fragmentation across agencies. We conducted a comprehensive assessment of all major water flows into, out of and within the CMAP region using an open access tool, R package CityWaterBalance, to create a reproducible workflow. We automated most data collection steps and integrated disparate sources to estimate unknown flows over the period 2001-2010. Our quantitative portrait of the CMAP water system reveals the relative magnitudes of all flows and how they are connected, quantitatively illustrating how a change in one part of the system can influence others. This assessment can be used to guide future planning efforts and as a basis for analyzing related sectors, such as energy or finance, for a broader understanding of the urban system. Our process greatly simplifies the work of accounting for urban water flows, and can be readily applied to other urban areas.
Description:
Urban water systems are complex and tightly coupled. In Chicago, the third largest US city, wastewater treatment plant (WWTP) effluent comprises up to 70% of streamflow, more than half of which is withdrawn for thermoelectric power generation (PG). Despite the interdependence of users and mass conservative behavior of water flows, monitoring and management efforts are highly fragmented. Here we comprehensively analyze the urban water system in greater Chicago during water years 2001-2010 and examine longer trends in coupled flows. Our study area is defined by the seven counties that are served by the Chicago Metropolitan Agency for Planning (CMAP). We use a reproducible workflow codified in our newly developed R package CityWaterBalance to automate data retrieval and quantify the relative magnitudes of measured and unmeasured flows through the CMAP region. Among other insights, our system-level assessment reveals the comparable long-term (10-yr) average magnitudes between a) Lake Michigan withdrawals and river inflow, b) total effluent (WWTP and PG) and river outflow, c) sewer infiltration and combined sewer overflow. Finer scale examination of temporal trends reveals significant reductions in potable water use and sewer overflows, and steady wastewater effluent volumes despite increased precipitation in recent years. Although a wealth of open data is available to study this region, discrepancies in spatial and temporal resolution preclude finer analysis of all system components at a scale relevant to CMAP. However, the increasing availability of web-served data will improve our ability to assess and compare urban water flows and to inform management decisions.