ERI: Effects of urban water infrastructure and proximate soil profiles on coupled surface-subsurface hydrology

Urban flooding and water quality issues are putting pressure on urban water infrastructure. In the next two decades, hundreds of billions of dollars will be invested in the repair and enhancement of wastewater, stormwater, and combined sewer systems to address challenges arising from urbanization and climate change in the United States. This infrastructure is “leaky” and, therefore, interacts with the surrounding soils and the water cycle.

However, the associated hydrologic processes, i.e., subsurface flows of drinking water, stormwater, and groundwater, are often overlooked or insufficiently characterized in urban watershed studies. Do leaky sanitary and storm sewers recharge or discharge water from the watershed? How will a shift from gray to green stormwater infrastructure impact stormwater retention in watersheds with leaky sewers underneath?

Addressing the lack of fundamental scientific knowledge on how urban water infrastructure affects surface-subsurface hydrologic processes is imperative to making effective and resilient water infrastructure investments. The purpose of this work is to evaluate the effect of urban soil profiles and water distribution and collection infrastructure on urban water balances, improve urban hydrologic models to better quantify the costs and benefits of infrastructure rehabilitation, and ultimately contribute to the goal of developing resilient and reliable urban water systems.

The project will provide an efficient modeling tool to the urban drainage and hydrology community, enhance industry-research collaboration in drainage and water resources in the Midwest, and develop an “Urban Hydrology and Stormwater Management” curriculum that is available to undergraduate and graduate students across the University of Minnesota campuses.

The sustainability and resilience of urban water systems is limited by poor understanding of subsurface hydrologic processes that control flood generation and how they are impacted by urban soil profiles and water distribution and collection infrastructure. These subsurface flows of drinking water, stormwater, wastewater, and groundwater are less characterized in most hydrologic studies and urban hydrologic models.

Therefore, there is an urgent need to quantify subsurface hydrologic processes and their interaction with surface infiltration-runoff partitioning in urban watersheds. This project will quantify the effects of urban soil profiles and water distribution and collection infrastructure on event-scale runoff generation and longterm water balances. This will be achieved by integrating soil profile surveys with hydrologic model simulations.

First, this work will characterize the soil profiles near water distribution and collection system pipes through soil core sampling and hydraulic profiling. Then, this work will develop a surface-subsurface hydrologic model parameterization that can represent infiltration and exfiltration fluxes between water infrastructure and the unsaturated/saturated zones.

Lastly, this work will evaluate the relative effects of soil profiles and sewer pipe conditions and layouts on flood response and long-term water balances through hypothetical simulations at lot and catchment scales. This study focuses on urban watersheds in Milwaukee, WI, while the approach and results are applicable across other urban watersheds in the United States.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.