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Stormwater-Stream Connectivity: Process, Context, and Tradeoffs

In a few minutes, I’ll be giving a cyberseminar in CUAHSI’s fantastic sustainable urban streams seminar series. You can join the seminar live at 3:30 pm, or watch a recording of it later. Either way, https://www.cuahsi.org/Posts/Entry/13551 is where you want to go to watch and listen. If you want to know what you’re in for, I’ve attached my late-breaking abstract below. The whole series has been really superb, with great speakers making key points about the state-of-the-science in urban streams and watersheds. I’m honored to be part of the lineup, and I encourage you to check out all of the recordings. Enjoy!

Stormwater-Stream Connectivity: Process, Context, and Tradeoffs

Anne Jefferson

Streams in urban areas are often said to suffer from “urban stream syndrome” resulting in degraded geomorphology, biogeochemistry, and ecosystem function. Uncontrolled or poorly controlled stormwater is a root cause of many of the symptoms of urban stream syndrome, so understanding how stormwater management options affect in-stream processes is important for creating sustainable urban streams. Today’s approaches to stormwater control include green infrastructure distributed throughout the watershed and more centralized stormwater control ponds and wetlands located near the stream. How well do these approaches minimize risks to human health and infrastructure and protect aquatic ecosystems? In this talk, I’ll suggest that the answer depends on three factors: context; process; and tradeoffs. In terms of context, watersheds and stormwater management efforts are situated within a particular natural landscape (climate, soils, etc.); relative to urban development (age and style of development, type of infrastructure); and within the social context of environmental attitudes and economic constraints and incentives. Processes upslope of stormwater controls that affect water quantity and quality and processes within the controls themselves, such as mixing, infiltration and residence time, exert significant influence on how urban stream hydrology, water quality, and ecology responds to stormwater inputs. Where stormwater ponds and wetlands (SCMs) are large inputs to a stream, they can impart distinct water quality signals, and such SCMs are unlikely to restore pre-development stream water quantity and quality. Distributed green infrastructure shows promising reductions in peakflows and total stormwater volumes at the street-scale, but challenges remain in scaling up to enough projects to make a difference at the watershed scale and in ensuring that variability in construction and maintenance don’t reduce the effectiveness of the green infrastructure. Finally, there are tradeoffs in our choices around stormwater management infrastructure, in terms of the broader environmental benefits it can provide versus a more narrow focus on water quantity and quality. Using an ecosystem services framework, I show one approach to examining these tradeoffs. None of the current approaches to managing stormwater are a panacea, but with process-based, contextual studies that also examine limitations and tradeoffs, we can move the science and practice of stormwater management toward better outcomes and more sustainable urban streams.

After the dam comes down: groundwater-stream interactions and water quality effects of restored and unrestored reaches in northeastern Ohio

The Watershed Hydrology lab will be out in force for the Geological Society of America annual meeting in Vancouver in October. For the last few days, we’ve been sharing the abstracts of the work we are presenting there.

AFTER THE DAM COMES DOWN: GROUNDWATER-STREAM INTERACTIONS AND WATER QUALITY EFFECTS OF RESTORED AND UNRESTORED REACHES IN NORTHEASTERN OHIO

BROWN, Krista Marie, Geology, Kent State University, Kent, OH 44240, kbooth@kent.edu and JEFFERSON, Anne J., Department of Geology, Kent State University, 221 McGilvrey Hall, Kent, OH 44240

Over that past decade, dam removals have become increasingly popular, as many dams near the end of their life expectancy. With an anticipated increase of dam removals in coming years, this study aims to develop an understanding of groundwater-stream interactions and water quality in former reservoirs after dam removal. Low head dams were removed in 2009 on Plum Creek and Kelsey Creek, tributaries to the Cuyahoga River. Kelsey Creek reservoir remains unaltered and consists of a stream channel flowing through riparian-wetland environments, while Plum Creek reservoir underwent channel restoration in 2011. At Kelsey Creek, 20 piezometers and 3 wells were installed within the former reservoir. Since October 2013, hydraulic heads have been recorded semi-weekly for aquifer modeling and water samples have been taken in the wells and stream. Water quality is being evaluated with field-measured parameters and ion chromatography. Plum Creek is being used to understand the water quality effects of channel restoration.
At Kelsey Creek, interaction between the stream and shallow groundwater is evident. The stream tends to contribute shallow groundwater flow toward the western side of the site and north, parallel to the stream. The well closest to the stream shows variability in specific conductance, indicating bidirectional groundwater-stream exchange and all wells show rapid response to precipitation events. Hydraulic conductivity calculated using the Hvorslev method ranged 2.84×10-2to 7.38×10-6 m/s and poorly correlate with the bulk sediments in Kelsey Creek.
Despite the wetland and groundwater-stream exchange in the unrestored Kelsey Creek, there is little change in stream water quality within the former reservoir site, similar to the restored Plum Creek site. This suggests that there is little water quality benefit to be gained from stream restoration at dam removal sites. Left unaltered, Kelsey Creek provides flood control and groundwater recharge in wetland areas.

Sensitivity of precipitation isotope meteoric water lines and seasonal signals to sampling frequency and location

The Watershed Hydrology lab will be out in force for the Geological Society of America annual meeting in Vancouver in October. Over the next few days, we’ll be sharing the abstracts of the work we are presenting there.

SENSITIVITY OF PRECIPITATION ISOTOPE METEORIC WATER LINES AND SEASONAL SIGNALS TO SAMPLING FREQUENCY AND LOCATION

REYNOLDS, Allison R., Department of Geology, Kent State University, 221 McGilvrey Hall, Kent, OH 44242, areyno13@kent.edu and JEFFERSON, Anne J., Department of Geology, Kent State University, 221 McGilvrey Hall, Kent, OH 44240
Every precipitation event has its own isotopic signature, making it useful for hydrology purposes, like estimating transit time or identifying seasonality of groundwater recharge. Our purpose is to compare the seasonal signal and local meteoric water line (LMWL) generated by one year of event-based sampling to those resulting from multi-year monthly sampling at the closest Global Network of Isotopes in Precipitation (GNIP) stations. The question we seek to answer is whether data from different sampling strategies, periods, and locations within the eastern Great Lakes region in North America converge on a regional-scale LMWL and seasonal signal.
From October 2012-present precipitation samples were collected in Kent, Ohio, filtered and analyzed by a Picarro L-2130i at Kent State University. The closest GNIP sites are Coshocton, Ohio, USA and Simcoe, Ontario, Canada; monthly data was downloaded from a database. For each site, we graphed the ?18O versus ?2H and added a linear trendline to represent the LMWL and fit sine waves to the data to assess seasonal isotopic signal.
Based on the event data, Kent has the most isotopically depleted precipitation, but when looking at monthly samples, it falls between Simcoe to the north and Coshocton to the south. This suggests that, in this region, isotopically light precipitation events are more important in terms of their frequency than their amount. LMWLs for each site were similar. Comparing the LMWLs generated from the event samples and monthly data, monthly data had a slightly lower slope and d-excess. For Coshocton, amplitude of the seasonal sine wave for ?18O is 6.2‰, for Simcoe the sine wave is 4.3 ‰. For the Kent dataset, event-based data produced a sine wave with amplitude of 6.1‰, while monthly data resulted in a 4.9‰ amplitude wave. While it is possible that the amplitude of a wave fit to monthly data would increase with data points that represent isotopically extreme months, it is likely that curves fit to monthly data will frequently under-represent the variability in precipitation isotopes as measured at event and sub-event timescales. Both the LMWL and seasonal signal analysis suggest a greater variability in precipitation isotope signatures during the winter relative to the summer in the eastern Great Lakes region.

Changes in hyporheic exchange and subsurface processes following stream restoration

The Watershed Hydrology lab will be out in force for the Geological Society of America annual meeting in Vancouver in October. Over the next few days, we’ll be sharing the abstracts of the work we are presenting there.

CHANGES IN HYPORHEIC EXCHANGE AND SUBSURFACE PROCESSES FOLLOWING STREAM RESTORATION

BAKER, Stuart B., Department of Geology, Kent State University, 221 McGilvrey Hall, 325 S. Lincoln St, Kent, OH 44242, sbaker51@kent.edu and JEFFERSON, Anne J., Department of Geology, Kent State University, 221 McGilvrey Hall, Kent, OH 44240
Stream restoration is a billion dollar industry with major goals of improving water quality and degraded habitat, yet restoration often falls short of significant improvements in toward these objectives. At present, there are limited data and understanding of the physical and biogeochemical responses to restoration that constrain the potential for water quality and ecological improvements. Hyporheic exchange, the flow of water into and out of the streambed, is an important stream process that serves a critical role in naturally functioning streams, allowing for stream water to interact with the substrate in various processes. Hyporheic flowpaths can be altered by the transport of fine sediment through the stream bed and are thus susceptible to changes in sediment regime and hydraulics, as well as the changes wrought by construction of a restoration project. The goal of this research is to determine the effect of restoration on hyporheic exchange and associated biogeochemical processes. Preliminary results from Kelsey Creek, OH, a second-order stream restored in August 2013, show a slight decrease in average hydraulic conductivity but an increase in heterogeneity from pre-restoration (geometric mean 8.47×10-5 m/s, range 2.67×10-5-3.05×10-4) to four months post-restoration (geometric mean 4.40×10-5 m/s, range 1.18×10-6-1.19×10-3) to ten months post-restoration (geometric mean 1.41×10-5 m/s, range 1.11×10-6-6.40×10-4) in piezometer nests through large constructed riffle structures. These piezometers also indicate dominance of downwelling throughout riffle structures with only isolated locations of upwelling. A stream in Holden Arboretum, OH restored in April 2014 had no significant change in average hydraulic conductivity between 1 and 2 months post-restoration, but many individual piezometers had increases of over 100% or decreases of over 50%. The greater variation in hydraulic conductivities in both restored streams may be adjustment from disturbance to a new dynamic equilibrium. Transient storage and hyporheic exchange were also measured with resazurin injections pre-restoration and post-restoration, and nutrient injections of NH4Cl will compare the nitrogen uptake rates of the restored reach to an unrestored reach downstream.

The effects of biogeochemical sinks on the mobility of trace metals in an area affected by acid mine drainage, Huff Run, Ohio

The Watershed Hydrology lab will be out in force for the Geological Society of America annual meeting in Vancouver in October. Over the next few days, we’ll be sharing the abstracts of the work we are presenting there.

THE EFFECTS OF BIOGEOCHEMICAL SINKS ON THE MOBILITY OF TRACE METALS IN AN AREA AFFECTED BY ACID MINE DRAINAGE, HUFF RUN, OHIO

TRAUB, Eric L., Department of Geology, Kent State University, 325 S. Lincoln St, 221 McGilvrey Hall, Kent, OH 44240, etraub@kent.edu, JEFFERSON, Anne J., Department of Geology, Kent State University, 221 McGilvrey Hall, Kent, OH 44240, and SINGER, David M., Department of Geology, Kent State University, 228 McGilvrey Hall, Kent, OH 44242
Currently, a watershed restoration group has made progress in remediating surface water contributions to the Huff Run Stream in Mineral City, OH, which is heavily affected by acid mine drainage (AMD) due to historical coal mining. However, the accumulation of AMD sediments on the streambed has prevented the overall ecological health of the area from rebounding. A proposed remediation plan includes dredging, however the efficacy of doing so while preventing further iron buildup and the potential release of trace metals during such an operation is uncertain. The objectives of this research are to examine the effects geochemical sinks can have on the fate and transport of trace metals in order to understand the possible side effects of dredging on the Huff Run. This work aims to build a framework on which to base proposed remediation plans at a wide range of acid-mine drainage impacted sites. To achieve these objectives cores were gathered from the Huff Run and the Farr tributary, where a large amount of AMD is discharged into the Huff Run. These core sediments were analyzed through XRD analysis to understand the abundance and distribution of mineral phases, and ICP analysis to provide information on the amount of trace metals and understand what mineral phases they are associated with. Groundwater piezometers installed in AMD-bearing sediments and streambed sediment were used to quantify changes in trace metals concentrations. The analyses of cores gathered from the stream provide evidence that overtime deposited iron oxides go through thermodynamic transformations into more stable phases, mainly goethite. On-going work aims to determine how mineralogical transformations impact the availability of trace metals. Hydraulic head values gathered the piezometers have shown that hyporheic exchange is occurring, despite the deposition of fine grained sediment and iron oxides from historical mining. Water samples collected from the piezometers have been analyzed for pH and conductivity and show consistent changes as the water is exchanged from the surface and groundwater. On-going work aims to determine how this exchange affects the transport of trace metals.

Assessing hydrologic impacts of street-scale green infrastructure investments for suburban Parma, Ohio

The Watershed Hydrology lab will be out in force for the Geological Society of America annual meeting in Vancouver in October. Over the next few days, we’ll be sharing the abstracts of the work we are presenting there.

ASSESSING HYDROLOGIC IMPACTS OF STREET-SCALE GREEN INFRASTRUCTURE INVESTMENTS FOR SUBURBAN PARMA, OHIO

JARDEN, Kimberly, Department of Geology, Kent State University, 221 McGilvrey Hall, Kent State University, 325 South Lincoln St, Kent, OH 44242, kjarden@kent.edu, JEFFERSON, Anne J., Department of Geology, Kent State University, 221 McGilvrey Hall, Kent, OH 44240, GRIESER, Jenn, Cleveland Metroparks, 2277 W Ridgewood Dr, Parma, OH 44134, and SCHAFER, Derek, West Creek Conservancy, Cleveland, OH 44134
Impervious surfaces in urban environments can lead to greater levels of runoff from storm events and overwhelm storm sewer systems. Disconnecting impervious surfaces from storm water systems and redirecting the flow to decentralized green infrastructure treatments can help lessen the detrimental effects on watersheds. Most research on green infrastructure has focused on the performance of individual elements, whereas this project addresses the question of hydrologic impacts and pollution reduction of street scale investments using green infrastructure best management practices (BMPs), such as front yard rain gardens, street side bioretention, and rain barrels. The West Creek Watershed is a 36 km2 subwatershed of the Cuyahoga River that contains ~35% impervious surface. Before-after-control-impact design pairs two streets with 0.001-0.002 ha. lots and two streets with 0.005-0.0075 ha. lots. Flow meters have been installed to measure total discharge, velocity, and stage pre– and post-BMP construction. Runoff data have been analyzed to determine if peak discharge for storm events has been reduced after installation of BMPs on the street with 0.001-0.002 ha. lots. Initial results show that the peak flows have not been reduced for most storm events on the street with the green infrastructure. However, several larger events show that peak flows have been reduced on the treatment street and need to be further investigated to determine what conditions led to flow reductions from these storms but not other events. Initial results for centroid lag-to-peak, centroid lag, lag-to-peak, and peak lag-to-peak show that lag times have increased on the treatment street. Additional research will include analysis of the total effect of street-scale BMPs on storm hydrograph characteristics including, hydrograph recession behavior and total runoff volume. Water samples are being collected at the end of each street during storm events to evaluate the ability of the BMPs to remove heavy metal pollutants from stormwater runoff. After studying the effect of each treatment street, we will define the level of disconnected impervious surfaces needed in order to reduce peak flows within the West Creek watershed.

Rayleigh isotope distillation module – development and transferability in geoscience education

The Watershed Hydrology lab will be out in force for the Geological Society of America annual meeting in Vancouver in October. Over the next few days, we’ll be sharing the abstracts of the work we are presenting there.

RAYLEIGH ISOTOPE DISTILLATION MODULE – DEVELOPMENT AND TRANSFERABILITY IN GEOSCIENCE EDUCATION

GRIFFITH, Elizabeth M., Earth and Environmental Sciences, University of Texas at Arlington, 500 Yates St, Arlington, TX TX 76019, lgriff@uta.edu, ORTIZ, Joseph D., Department of Geology, Kent State University, 221 McGilvrey Hall, Kent, OH 44242, JEFFERSON, Anne J., Department of Geology, Kent State University, 221 McGilvrey Hall, Kent, OH 44240, DEES, David, Faculty Professional Development Center and School of Foundations, Leadership and Administration, Kent State University, 231 Moulton Hall, Kent, OH 44242, and MERCHANT, William, Department of Evaluation and Measurement, Kent State University, 111L Nixon Hall, Kent, OH 44242
Rayleigh distillation is an important concept in geochemistry – applied to isotopic and elemental systems ranging from crystallization in magma chambers to oxygen isotope stratigraphy across glacial-interglacial periods. A teaching module that allows students to discover first-hand consequences of isotopic fractionation and Rayleigh distillation was developed, peer-reviewed, modified and used in thre upper-division geoscience courses: Sedimentology/Stratrigraphy, Environmental Geochemistry and Paleoceanography. In the module “Rayleigh isotope effect in the oceans: building glaciers” students perform (or are given data from) a simple batch distillation experiment that they model using open system Rayleigh isotopic fractionation. Insight on isotopic fractionation during phase transitions and a fundamental understanding of oxygen isotope stratigraphy is learned first-hand by the students preforming simple experiments and analyzing the data on sophisticated equipment. The teaching module is adaptable for the geoscience curriculum, including upper division courses and introductory courses. The module has only been tested in three upper division courses, but future work adapting and implementing the activity in an Introduction to Oceanography lab is planned.
Funding by the NSF Division of Undergraduate Education allowed us to study the impact on student learning and motivation from teaching the material within the module using different pedagogical approaches including a paper-based data analysis activity and hands-on data collection with and without access to the water isotope analyzer. Assessment techniques were developed and implemented through the close collaboration with a faculty expert within the educational field. The 3-year project is in its second year and initial quantitative results and reflections from the faculty and students will be presented. Both faculty noted a difference in the classroom dynamic with the students performing the experiments vs those completing the paper-based data analysis. Additional strategies will be highlighted for the transferability of the hands-on experiment to institutions and departments without access to the water isotope analyzer.

Hands-on experiences with stable isotopes in the geosciences curriculum

The Watershed Hydrology lab will be out in force for the Geological Society of America annual meeting in Vancouver in October. Over the next few days, we’ll be sharing the abstracts of the work we are presenting there.

HANDS-ON EXPERIENCES WITH STABLE ISOTOPES IN THE GEOSCIENCES CURRICULUM

JEFFERSON, Anne J.1, GRIFFITH, Elizabeth M.2, ORTIZ, Joseph D.1, DEES, David3, and MERCHANT, William4, (1) Department of Geology, Kent State University, 221 McGilvrey Hall, Kent, OH 44242, ajeffer9@kent.edu, (2) Earth and Environmental Sciences, University of Texas at Arlington, 500 Yates St., Arlington, TX 76019, Arlington, TX TX 76019, (3) Faculty Professional Development Center and School of Foundations, Leadership and Administration, Kent State University, 231 Moulton Hall, Kent, OH 44242, (4) Department of Evaluation and Measurement, Kent State University, 111L Nixon Hall, Kent, OH 44242

Over the past thirty years, environmental and geoscience research has increasingly utilized stable isotope ratios to understand problems as diverse as paleoclimates, magma genesis, and processes in the hydrosphere and critical zone. New laser-based technology for measuring isotope ratios has significantly reduced the cost of setting up and maintaining an isotope lab. The new technology is also easier to use with students than traditional isotope ratio mass spectrometers, so there is strong potential to introduce hands-on experiences into the geoscience curriculum.
This project, funded by the NSF Division of Undergraduate Education, assessed the impact that different pedagogical approaches have on student learning of stable isotope concepts in upper-division geoscience courses (Watershed Hydrology; Sedimentology/Stratigraphy; Environmental Geochemistry). Groups of students were exposed to this content via (1) a lecture-only format; (2) a paper-based data analysis activity; and (3) hands-on data collection, sometimes including spectrometer analysis. Pre- and post-tests measured gains in content knowledge while approaches to learning and motivational questionnaires instruments were used to identify the effects of the classroom environment on learning approaches and motivation. Focus group interviews were also conducted to verify the quantitative data. Preliminary findings of this study, currently in year two of three, include: a) a common decrease in student motivation as the semester progresses, b) relatively minor changes in student approaches to learning regardless of pedagogical strategy, and c) students’ positive responses to professor passion.
Peer review of modules and activities has been used to ensure high quality content is being delivered. Close collaboration between geosciences and education faculty at all project stages has enabled deployment of robust measures of student learning, increased responsiveness of the research to developments in the classroom, and facilitated exploration of unexpected project results. In its final year, the project will focus on high-impact dissemination of developed curriculum and project results, through workshops and on-line repositories.

Development of hyporheic exchange and nutrient uptake following stream restoration

Next week, the Watershed Hydrology Lab will be well represented at the CUAHSI 2014 Biennial Colloquium. We’ll be presenting four posters, so here come the abstracts…

Development of hyporheic exchange and nutrient uptake following stream restoration

Stuart Baker and Anne Jefferson

Stream restoration is a multi-million dollar industry in Ohio, with major goals of improving water quality and degraded habitat. Yet restoration often falls short of significant improvements in water quality and biodiversity. It is thus important to improve the theory and practice of stream restoration in order to achieve greater benefits per dollar spent, yet there are limited data and understanding of the physical and biogeochemical responses to restoration that constrain the potential for water quality and ecological improvements. Hyporheic exchange, the flow of water into and out of the streambed, is an important stream process that serves critical roles in naturally functioning streams, allowing for stream water to participate with the substrate in various processes. Hyporheic flowpaths can be altered by the transport of fine sediment through the stream bed and are thus susceptible to changes in sediment regime and hydraulics, as well as the changes wrought by construction of a restoration project. The goal of this research is to determine the effectiveness of restoration in enhancing hyporheic flow and associated biogeochemical processes to improve water quality. Preliminary results from Kelsey Creek, OH, a second-order stream restored in August 2013, show a decrease in average hydraulic conductivity but an increase in heterogeneity from pre-restoration (geometric mean 8.47×10-5 m/s, range 1.18×10-6-1.19×10-3) to post-restoration (geometric mean 4.41×10-5 m/s, range 2.67×10-5-3.05×10-4) in piezometer nests through large constructed riffle structures. These piezometers also indicate dominance of downwelling throughout riffle structures with only isolated locations of upwelling. Transient storage and hyporheic exchange will be measured with resazurin injections for comparison between pre-restoration and post-restoration, and nutrient injections of NH4Cl at time points following the restoration will compare the nitrogen uptake rates of the restored reach to an unrestored reach downstream. Additional sites are planned for study to include restoration projects of different ages to examine the development of hyporheic exchange and biogeochemistry after completion of restoration projects.

Stormwater control measures modify event-based stream temperature dynamics in urbanized headwaters

Next week, the Watershed Hydrology Lab will be well represented at the CUAHSI 2014 Biennial Colloquium. We’ll be presenting four posters, so here come the abstracts…

Stormwater control measures modify event-based stream temperature dynamics in urbanized headwaters

Grace Garner1, Anne Jefferson2*, Sara McMillan3, Colin Bell4 and David M. Hannah1
1School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK.
2Department of Geology, Kent State University, Kent, OH, 44240, USA
3Department of Civil and Environmental Engineering, University of North Carolina at Charlotte, Charlotte, NC, 28223, USA
4Department of Infrastructure and Environmental System, University of North Carolina at Charlotte, Charlotte, NC, 28223, USA

Urbanization is a widespread and growing cause of hydrological changes and ecological impairment in headwater streams. Stream temperature is an important control on physical, chemical and ecological processes, and is an often neglected water quality variable, such that the effects of urban land use and stormwater management on stream temperature are poorly constrained. Our work aims to identify the influence of stormwater control measures (SCMs) of differing design and location within the watershed on the event-based temperature response of urban streams to precipitation in the North Carolina Piedmont, in order to improve prediction and management of urban impacts. Stream temperature was measured within SCMs, and upstream and downstream of them in two streams between June and September 2012 and 2013. Approximately 60 precipitation events occurred during that period. To unambiguously identify temperature increases resulting from precipitation, surges were identified as a rise in water temperature of ?0.2°C between the hours of 15:30 and 5:30, when the diurnal temperature cycle is either decreasing or static on days without precipitation. Surges up to 5°C were identified in response to precipitation events, with surges occurring both upstream and downstream of the SCM under some conditions. Surges were also recorded within the SCMs, confirming that temperature surges are the result of heated urban runoff. Classification tree modeling was used to evaluate the influence of hydrometeorological drivers on the generation and magnitude of temperature surges. In both streams, event precipitation, antecedent precipitation, and air temperature range were identified as the drivers of whether or not a surge was observed and how large the surge was, though the order and thresholds of these variables differed between the two sites. In a stream with an off-line, pond SCM, the presence of the pond in the lower 10% of the watershed did not affect the magnitude of temperature surges within the stream, but the pond itself had a wider range of surge magnitudes than did the stream. In a watershed with a large in-line pond, and a downstream contributing wetland SCM receiving flow from 40% of the watershed, the wetland increased both the frequency and magnitude of temperature surges observed in the stream. Our results suggest dynamic hydrometeorological conditions, SCM design, and position within a watershed all influence whether stormwater management reduces or enhances temperature surges observed within urban headwater streams, and that these factors should be considered in the recommendations for urban stormwater management systems.