Streamflow generation is linked to water quality dynamics in urban headwater streams
Abstract
Steep rising limbs and high peak flows are the hallmarks of urban stream hydrographs, as a result of stormwater runoff from impervious surfaces. Conflating urban streams and stormwater, however, misses the multiple anthropogenic and natural sources of flow that combine to create the hydrologic and water quality signatures of urban streams. Beyond stormwater runoff, leaky water and sewer pipes, municipal and industrial effluent, irrigation, and green infrastructure can all add to the remnant natural flow generation mechanisms at work in urban watersheds. Teasing apart the sources of flow, and their connection to the urban environment, may be very helpful for interpreting water quality dynamics and appropriately managing urban water resources.
Water and nitrate stable isotopes, along with concentration-discharge relationships, allow us to examine stormflow and baseflow sources, and to link hydrologic and water quality dynamics to watershed land cover and infrastructure in three study watersheds with variable configurations of urban development, buried reaches, and forested areas. In the three northeast Ohio headwater streams, baseflow is largely supplied by road salt-contaminated shallow groundwater, with nitrate sourced from leaky sewers. During large summer storms, event water dominates the hydrograph, diluting chloride and contributing atmospherically-derived nitrate, which is washed off of impervious surfaces by stormwater runoff. Nitrate concentrations may increase, decrease, or stay steady during storms, depending on the relationship between pre-event sewage contributions and stormwater runoff volumes. Thus, hydrologic and water quality dynamics vary among streams, based on connectivity between the stream and its watershed's urban infrastructure.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.H34F..05J
- Keywords:
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- 1804 Catchment;
- HYDROLOGY;
- 1813 Eco-hydrology;
- HYDROLOGY;
- 1839 Hydrologic scaling;
- HYDROLOGY;
- 1847 Modeling;
- HYDROLOGY