Details

Autor(en) / Beteiligte

• Zhang, Kun
• Sebo, Spencer
• McDonald, Walter
• Bhaskar, Aditi
• Shuster, William
• Stewart, Ryan D.
• Parolari, Anthony J.

Titel

The Role of Inflow and Infiltration (I/I) in Urban Water Balances and Streamflow Regimes: A Hydrograph Analysis Along the Sewershed‐Watershed Continuum

Ist Teil von

• Water resources research, 2023-04, Vol.59 (4), p.n/a

Ort / Verlag

Washington: John Wiley & Sons, Inc

Erscheinungsjahr

2023

Quelle

Wiley Online Library - AutoHoldings Journals

Beschreibungen/Notizen

• Urbanization alters subsurface flow pathways through expansion of sanitary collection and conveyance infrastructure. Inflow and infiltration (I/I) into sewers redistributes slow subsurface flows to fast within‐sewer flows. Acting in concert with connected surface water, redistribution through I/I complicates the net impact of urbanization on streamflow. Elucidation of these processes is key to the characterization and prediction of urban hydrologic cycles. In this study, we collected sanitary sewer flow and streamflow data from 17 sewersheds and 18 watersheds in and around Milwaukee, WI, USA. We compared flow duration curves and baseflow recession characteristics of I/I and streamflow in urban and reference watersheds. Median depth‐normalized I/I (296 mm) was nearly 35% of mean annual precipitation (867 mm), and thereby a major component of the urban drainage budget. I/I flowrates were similar to urban streamflow during high flow events (10th percentile) and larger during intermediate (50th percentile) and low (90th percentile) flow events. Further, I/I recession was slower and more nonlinear in shape than urban streamflow. Increased imperviousness and sewer density were associated with increased high flows, decreased intermediate flows, and quicker streamflow recessions. Sewer density explained more variability in intermediate flows (35%) and baseflow recession rate (49%) than imperviousness (24% and 19% respectively). Based on our findings, I/I takes up valuable volume capacity in sewers, which leads to more frequent overflows and alters streamflow regimes with ecological implications. Thus, I/I should be better considered in the prediction of urban hydrologic fluxes, and the characteristics and hydro‐ecologic impact of I/I should be more thoroughly explored. Plain Language Summary Urbanization brings with it sanitary collection and conveyance infrastructure, which alters system capacities, water budgets, and streamflow hydrographs. One unique component of the urban water cycle is inflow and infiltration (I/I), wherein there are inputs to the collection system from runoff, and exchange between underground conveyances and soil water and groundwater. These I/I impacts remain unclear for urbanized watersheds‐sewersheds. We examined and compared flow duration curves and baseflow recession characteristics of I/I, and streamflow in urbanized and minimally impacted reference watersheds. We found that I/I was 35 percent of the total urban water budget, with much of this contributing in the wet winter and spring seasons. Compared to streamflow, the hydrograph of I/I recessed more slowly and possessed a more convex shape. Although the amount of impervious area in a watershed is major contributor to inflows, we found that sewerage density had a comparable or even stronger influence on streamflow alteration. Based on our findings, I/I takes up valuable volume capacity in sewer systems, which can lead to more frequent overflows, and alters streamflow regimes with ecological implications. I/I should be better considered in urban water cycle, and the characteristics and hydro‐ecologic impact of I/I should be better studied. Key Points I/I was a major component of the urban drainage budget as 35% of mean annual precipitation inputs Increased imperviousness and sewer density explained increased high flows, decreased intermediate flows, and faster rate of flow recession The recession of I/I possesses higher nonlinearity or convexity than streamflow