Browsing by Author "Herb, William R."

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All-Weather Ground Surface Temperature Simulation
(St. Anthony Falls Laboratory, 2006-09) Herb, William R.; Janke, Ben; Mohseni, Omid; Stefan, Heinz G.
Thermal pollution from urban runoff is considered to be a significant contributor to the degradation of coldwater ecosystems. Impervious surfaces (streets, parking lots and buildings) are characteristic of urban watersheds. A model for predicting temperature time series for dry and wet ground surfaces is described in this report. The model has been developed from basic principles. It is a portion of a larger project to develop a modeling tool to assess the impact of urban development on the temperature of coldwater streams. Heat transfer processes on impervious and pervious ground surfaces were investigated for both dry and wet weather periods. The principal goal of the effort was to formulate and test equations that quantify the heat fluxes across a ground surface before, during and after a rainfall event. These equations were combined with a numerical approximation of the 1-D unsteady heat diffusion equation to calculate temperature distributions in the ground beginning at the ground surface. Equations to predict the magnitude of the radiative, convective, conductive and evaporative heat fluxes at a dry or wet surface, using standard climate data as input, were developed. Plant canopies were included for surfaces covered by vegetation. The model can simulate the ground surface and subsurface temperatures continuously throughout a specified time period (e.g. a summer season) or for a single rainfall event. Ground temperatures have been successfully simulated for pavements, bare soil, short and tall grass, trees and two agricultural crops (corn and soybeans). The simulations were first run for different locations and different years as imposed by the availability of measured soil temperature and climate data. Data came from sites in Minnesota, Illinois and Vermont. To clarify the effect of different land uses on ground temperatures, the calibrated coefficients for each land use and the same soil coefficients were used to simulate surface temperatures for a single climate data set from St. Paul, MN (2004). Asphalt and concrete give the highest surface temperatures, as expected, while vegetated surfaces gave the lowest. Bare soil gives surface temperatures that lie between those for pavements and plant-covered surfaces. The soil temperature and moisture model appears to model surface temperatures of bare soil and pavement with RMSEs of 1 to 2°C, and surface temperatures of vegetation-covered surfaces with RMSEs of 1 to 3oC. The plant canopy model used in this study, based on the work of Best and Deardorff, provides an adequate approximation for the effect of vegetation on surface heat transfer, using only a few additional parameters compared to bare surfaces. While further simplifications of the model are possible, such simplifications do not reduce the number of required input parameters, and do not eliminate the need for estimating the seasonal variation of the vegetation density. A model for roof temperatures was also developed, based on the surface heat transfer formulations used for pavement. The model has been calibrated for both a commercial tar/gravel roof and a residential roof. Compared to pavement, the roof surface reach similarly high maximum temperatures, but reach lower minimum temperature at night cool due to their lower thermal mass.
Analysis of Flow Data from Miller Creek, Duluth, MN
(St. Anthony Falls Hydraulic Laboratory, 2008-11) Herb, William R.; Stefan, Heinz G.
This report summarizes an analysis of flow and precipitation data for Miller Creek, a trout stream in Duluth, MN, which was undertaken in support of the MPCA-mandated temperature TMDL. The main goals of this analysis were to determine the availability and quality of Miller Creek flow data and to characterize typical summer low flow conditions to be used in subsequent stream temperature analysis. Flow data from the three existing flow aging sites (lower, middle, upper) on Miller Creek were analyzed, along with precipitation data from the Duluth International Airport. The analyses of flow and precipitation data suggest that the flow data at the lower site are relatively consistent for all years, except 2007. Flow data from the middle site for the periods 1997-2003 and 2004-2007 have different character, with the 2004-2007 data from the middle site considered suspect. Flow data from the upper site (Kohl’s) in 1997 and 1998 appear reasonable, but a rating curve does not exist to translate stage data to flow for 2003 – 2007. Relationships between stream flows and precipitation have been established at weekly timescales and are reasonable (r2 = 0.70), but with RMSEs similar in magnitude to the mean flows. Based on 1997 and 1998 data, weekly-averaged flows at the middle and upper gaging sites are, on average, 92% and 77% of the lower site, respectively. This suggests that a large fraction of the flow in Miller Creek originates from the upper portion of the watershed, upstream of the Kohl’s site. A statistical analysis of five years of flow data from the Miller Creek lower site indicates that low flows in the range of 1 to 2 cfs are quite common at weekly time scales. Therefore a rainfall event of moderate magnitude may be expected to have a significant impact on stream flow and temperature at the lower site. Although the flow record is relatively short (5 years), the results of a frequency analysis suggest that weekly mean flows near zero are possible with a 10 year return period.
Analysis of Stream Temperature Data from Miller Creek, Duluth, MN
(St. Anthony Falls Laboratory, 2009-10) Herb, William R.; Stefan, Heinz G.
This report summarizes an analysis of stream temperature and associated climate data for Miller Creek, a trout stream in Duluth, MN. The study was undertaken in support of an MPCAmandated temperature TMDL. The main goals of the analysis were 1) to characterize the spatial and temporal variations of stream temperature and 2) to determine the main drivers of stream temperature exceedances in Miller Creek. Stream temperature and flow data from 1997-98, 2003-05, and 2007-08 were analyzed at hourly to annual time scales. Included were water temperature data from the main stem of Miller Creek, its tributaries, and from storm sewer outlets to Miller Creek. Stream temperature in Miller Creek was found to be highly correlated to air temperature from the Duluth Airport at daily to annual time scales. Temperature exceedances (T > 20 ºC) were found to be caused mainly by strong atmospheric heat transfer to the stream due to low channel shading in the middle reaches of Miller Creek. Only 5 to 10% of all temperature exceedances appear to be associated with surface runoff from rainfall events, and even fewer are associated solely with surface runoff. Little evidence was found that lower stream flow leads to increased stream temperature and more frequent temperature exceedances. In mid summer tributaries of Miller Creek are typically at a lower temperature than the main stem of Miller Creek. The tributary at Chambersburg Ave. appears to measurably lower the temperature of the main stem, up to several degrees Celsius. The roles of groundwater and wetlands in the water (flow) and heat budgets of Miller Creek can not be quantified based on the available stream temperature records.
An Analytic Model for Runoff and Runoff Temperature from a Paved Surface
(St. Anthony Falls Laboratory, 2006-10) Herb, William R.; Janke, Ben; Mohseni, Omid; Stefan, Heinz
Existing simplified runoff models such as SCS synthetic hydrographs give some ability to predict surface runoff, but are generally developed for larger watersheds, and do not necessarily represent the actual variation in flow rate with varying precipitation rate. For the purposes of simulating runoff rate and runoff temperature from small parcels of land, a new runoff model was developed based on Manning’s equation. The runoff model is analytical and spatially integrated (zero-dimensional), in that flow depth, flow rate and runoff temperature are computed at one point, the outlet. By taking into account expected variations in the upstream flow depth, the model closely matches the simulations results of a 1D kinematic wave model. The analytic runoff model was coupled to a 1D soil temperature and moisture model, to enable simulation of infiltration, runoff rate and runoff temperature.
An Analytic Model for Runoff and Runoff Temperature from a Paved Surface
(St. Anthony Falls Laboratory, 2006-10) Herb, William R.; Janke, Ben; Mohseni, Omid; Stefan, Heinz G.
Existing simplified runoff models such as SCS synthetic hydrographs give some ability to predict surface runoff, but are generally developed for larger watersheds, and do not necessarily represent the actual variation in flow rate with varying precipitation rate. For the purposes of simulating runoff rate and runoff temperature from small parcels of land, a new runoff model was developed based on Manning’s equation. The runoff model is analytical and spatially integrated (zero-dimensional), in that flow depth, flow rate and runoff temperature are computed at one point, the outlet. By taking into account expected variations in the upstream flow depth, the model closely matches the simulations results of a 1D kinematic wave model. The analytic runoff model was coupled to a 1D soil temperature and moisture model, to enable simulation of infiltration, runoff rate and runoff temperature.
Characterization of Stream Temperature and Heat Loading for Miller Creek, Duluth, Minnesota
(St. Anthony Falls Laboratory, 2011-08) Herb, William R.
This report summarizes a study of heat loading and stream temperature in Miller Creek in support of the MPCA Miller Creek temperature TMDL. The work described here builds on previous work done at St. Anthony Falls Lab (Erickson et al. 2009, Herb and Stefan 2009a, 2009b, 2009c.) to include 2009 monitoring data and to characterize temperatures and heat inputs based on both daily and weekly temperature standards.
Climate Change Adaptation of Urban Stormwater Infrastructure
(Minnesota Department of Transportation, 2023-06) Erickson, Andrew J.; Herb, William R.; Gallagher, Noah D.; Weiss, Peter T.; Wilson, Bruce N.; Gulliver, John S.
The final analysis of historical (TP-40), current (Atlas 14), and future predicted storm events for three watersheds in Minnesota (Duluth, Minneapolis, Rochester) has shown that current design philosophy is not sufficient to prevent flooding from 10-year and larger design storm events and that flood depth and duration will increase given current climate projections. Several stormwater infrastructure adaptation strategies were assessed for reducing flood depth and duration: Baseline (existing conditions), adding rain gardens (aka, Infiltration Basins), adding new wet ponds, retrofitting existing stormwater ponds to be ?Smart Ponds, adding new Smart Ponds while also converting existing ponds into Smart Ponds, or upsizing of stormwater pipes to convey more water. In watersheds that are mixed urban, suburban, and rural like Rochester?s Kings Run or Duluth?s Miller Creek sub-watersheds, the most cost-effective climate change adaptation strategy was to build new stormwater wet ponds (Extra Ponds strategy) to treat the impervious surfaces not currently treated by existing wet ponds and other stormwater BMPs. In the fully developed urban 1NE watershed in Minneapolis, the most cost-effective (excluding land costs) climate change adaptation strategy was building wet ponds (Extra Ponds). Securing property for building new stormwater infrastructure in fully developed urban watersheds like 1NE may be a substantial cost compared to other watersheds. Smart Ponds do not require additional land for implementation and thus represent a relatively low-cost alternative that will be more beneficial in watersheds with numerous existing wet ponds.
Estimation of Groundwater Inflow to the Vermillion River from Observations of Stream Flow and Stream Temperature
(St. Anthony Falls Laboratory, 2009-11) Janke, Ben; Herb, William R.; Mohseni, Omid; Stefan, Heinz G.
A model has been developed for estimation of groundwater inflow to a stream reach from observations of stream temperature, groundwater temperature, stream flow rate, and standard weather parameters. The purpose of this model is to provide an estimate of groundwater inflow rate for stream reaches where groundwater inflow is significant. This information is useful for management of fisheries and urban development in watersheds where stream temperature is a concern. In particular, the model was developed for use in the Vermillion River, which has designated trout stream reaches that may be impacted by development in the watershed. The model estimates groundwater inflow rate from a stream reach heat budget, which takes into account atmospheric heat flux, sediment-water heat exchange, and groundwater inflow. The model requires the following data as input: stream temperature at the upstream and downstream ends of the stream reach, stream flow at either end of the reach, standard weather data, and no significant tributaries or inflows between the ends of the reach. The model was applied to six reaches in the Vermillion River watershed. Estimated groundwater inflow rates showed considerable spatial and temporal variability, both seasonally and between the two years simulated (2006 and 2007). In North Creek, groundwater inflow rate was 0.45 to 1.30 cfs/mile in 2007; in the upper Vermillion River main stem for the same period estimated inflow rates ranged from 0.15 to 3.87 cfs/mile. In the middle Vermillion River main stem, estimated inflow rates were unnaturally large and more variable (0.39 to 11.1 cfs/mile); these estimates include significant tributary inflow, which is lumped with groundwater inflow in the model. This, along with the failure of the model for reaches or periods involving high stream flows, is the likely source of the over-predicted groundwater inflow values. Simulations for lower South Creek showed negligible groundwater inflow for 2006; results for lower South Branch were very typical of a groundwater-fed stream, with relatively constant groundwater inflow (around 1.0 cfs/mile) that fluctuated only slightly during periods of heavy rainfall. A comparison of predicted groundwater inflow rates throughout the watershed for both dry (baseflow) and high-flow conditions suggest the presence of shallow groundwater, particularly in the lower reaches of the watershed. The significant variability in groundwater inflow rate predicted by the model can be traced to a number of factors, including data quality and sensitivity of the model to groundwater temperatures, stream shading/sheltering, and especially to stream flow. An extensive sensitivity analysis of the model is presented in this report, as well as an analysis of available data, in particular, groundwater temperature. Limitations of the heat budget approach to modeling groundwater inflow rate are also discussed and criteria for application of the model are developed from the results of sensitivity analysis.
Estimation of Runoff Temperatures and Heat Export from Different Land and Water Surfaces
(St. Anthony Falls Laboratory, 2007-02) Herb, William R.; Janke, Ben; Mohseni, Omid; Stefan, Heinz G.
This report describes work to analyze runoff temperatures and runoff heat export rates for a variety of terrestrial land covers and aquatic surfaces. Surface runoff temperatures and heat export have been simulated for ten terrestrial covers, an unshaded wet detention pond, a lake/reservoir, and a vegetated pond. A continuous simulation was run from April 1 to October 31, yielding a total of about 280 precipitation events for six years (1998-2000, 2003-2005). Six years of 15-minute climate data from the weather station at the MnROAD facility in Albertville, MN, were used as model input. In general, the variation in average runoff temperatures from terrestrial land covers and open water surfaces was moderate, from 24.9 °C for concrete to 21.5 °C for a forest. Pavements, commercial rooftops, bare soil, wet detention ponds, and lakes/reservoirs were all found to give runoff temperatures high enough to significantly impact stream temperature. Vegetated surfaces gave substantially lower runoff temperature and heat export than paved surfaces. Runoff temperatures from bare soils were consistently higher than from vegetated surfaces, but lower than from pavements. Residential roofs gave, on average, low runoff temperatures, due to very low thermal mass, while commercial roofs gave high runoff temperatures in some cases. Large water bodies (lakes and reservoirs) generally give very high runoff temperatures, but the quantity of runoff is highly dependent on the water level prior to the storm event. Analysis of a vegetated pond indicates that shading from emergent vegetation can reduce runoff temperature up to 6°C compared to an unshaded pond.
Extraction of pavement and soil thermal diffusivity from measured temperature times series
(St. Anthony Falls Laboratory, 2006-09) Herb, William R.; Marasteanu, Mihai; Stefan, Heinz G.
This report describes several methods to extract pavement thermal diffusivity from pavement temperature measurements at two or more depths. Two methods use analytic solutions for heat transfer in an infinite solid to relate the attenuation of diurnal temperature change with depth to thermal diffusivity. The first approach considers the surface temperature forcing to be a simple sinusoidal function with a period of one day. The second method considers the surface temperature forcing to be a general periodic signal that can be decomposed with a Fourier series. The accuracy of these two methods are limited by non-homogeneous nature of pavement/subgrade/soil systems. The third method uses a one-dimensional finite difference heat transfer model to extract thermal diffusivity from measured pavement temperature. This method requires more computational effort, but can take into account the variation in thermal diffusivity between the pavement and underlying layers.
A flow and temperature model for the Vermillion River, Part II: Response to surface runoff inputs
(St. Anthony Falls Laboratory, 2008-12) Herb, William R.; Stefan, Heinz G.
Stream temperature and stream flow are crucial physical parameters for aquatic habitat preservation in rivers and streams. Water temperature is particularly important in coldwater stream systems that support trout. Summer base (low) flow conditions with high water temperatures can be very detrimental to trout habitat. Surface runoff from rainfall events can lead to increases in stream temperature, particularly in developed (urban) watersheds. To better understand the interactions between stream temperature, land use, and climate, a stream thermal impact model has been developed for the Vermillion River, Minnesota. The model includes an unsteady streamflow and a water temperature model for the main stem of the Vermillion from Dodd Avenue to Goodwin Avenue and a number of tributaries, including South Branch, South Creek, North Creek, and Middle Creek. The EPD-riv1 package was used to simulate stream flow, including distributed groundwater inputs. A stream temperature model has been assembled based on previous work at SAFL. The stream temperature model uses flow and flow area from the flow solver, along with observed climate data to calculate surface heat transfer. The assembled flow and temperature model for the Vermillion River has been calibrated for baseflow conditions. Surface runoff inputs to the Vermillion River were simulated using a GIS-based land heat contribution model, which was developed and run by Applied Ecological Services. Surface runoff volume and temperature time series were simulated for a ½” rainfall event in 35 subwatersheds. Simulated runoff volumes and temperatures from the 35 sub-watersheds were used as input to the stream flow and temperature model, to simulate the hydraulic and thermal response of the Vermillion to runoff from the ½” rainfall event. Stream temperature increases due to surface runoff were found to be highest (1-4ºC) in smaller, upstream tributaries of South Creek and North Creek, and lowest in lower portions of the main stem and South Branch (< 1 ºC). Overall, the stream temperature response to multiple surface inflows was found to be quite complex. The coupled surface runoff and stream temperature model was used to examine several future urban development scenarios for the South Creek watershed and several possible strategies for mitigation of thermal impact downstream from the development. The model was able to resolve the stream temperature impact of a single 200 acre development. Full development in the upper South Creek watershed gave stream temperature increases over present conditions ranging from 3.8ºC in small tributaries to South Creek to less than 0.1ºC at the main stem of the Vermillion River near Empire. Downstream mitigation of thermal impacts from surface runoff was found to be ineffective, because the downstream watersheds were relatively undeveloped, and much of the thermal impact from upstream was lost by atmospheric heat transfer and dilution by the time the flow reached the sub-watersheds downstream. Adding channel shading to downstream stream reaches did not reduce the magnitude of the thermal impacts from upstream surface runoff, but did reduce maximum stream temperatures during dry weather periods, as would be expected.
Heating of Rainfall Runoff on Residential and Commercial Roofs
(St. Anthony Falls Laboratory, 2010-01) Janke, Ben; Mohseni, Omid; Herb, William R.; Stefan, Heinz G.
A common assumption in stream water temperature modeling is that rooftops of all types contribute very little heat to runoff from rainfall. In this report we examine the accuracy of this assumption (a) by analyzing temperature data which we recorded on a residential rooftop, a commercial rooftop, and a concrete driveway, and (b) by simulating temperature profiles within rooftops and pavements, and estimating heat transfer from these surfaces to rainfall runoff. Analysis of both wet‐ and dry‐weather temperature data which we recorded over periods of several months allowed us to conclude that a driveway has a far greater capacity for heat storage and release than a rooftop, although the commercial rooftop was able to store and release more heat than the residential rooftop. On sunny days and prior to rainfall, rooftops can reach higher temperatures than paved surfaces, but not much heat is stored, and roof temperatures drop rapidly as cloud cover increases with an approaching storm. Interestingly, weather events leading to the highest dew point (rainfall) and surface temperatures often occurred during late night or early morning hours, contrary to the expectation that the worst‐case runoff heating events would occur during daylight hours. The analysis conducted for three rainfall events showed that the heat export from the commercial rooftop was roughly three times that of the residential rooftop, but only 30%‐90% of the heat export from the concrete driveway. Potential heat export was significantly higher for the driveway than for either rooftop.
Heating of Rainfall Runoff on Residential and Commercial Roofs
(St. Anthony Falls Laboratory, 2010-01) Janke, Ben; Mohseni, Omid; Herb, William R.; Stefan, Heinz G.
A common assumption in stream water temperature modeling is that rooftops of all types contribute very little heat to runoff from rainfall. In this report we examine the accuracy of this assumption (a) by analyzing temperature data which we recorded on a residential rooftop, a commercial rooftop, and a concrete driveway, and (b) by simulating temperature profiles within rooftops and pavements, and estimating heat transfer from these surfaces to rainfall runoff. Analysis of both wet- and dry-weather temperature data which we recorded over periods of several months allowed us to conclude that a driveway has a far greater capacity for heat storage and release than a rooftop, although the commercial rooftop was able to store and release more heat than the residential rooftop. On sunny days and prior to rainfall, rooftops can reach higher temperatures than paved surfaces, but not much heat is stored, and roof temperatures drop rapidly as cloud cover increases with an approaching storm. Interestingly, weather events leading to the highest dew point (rainfall) and surface temperatures often occurred during late night or early morning hours, contrary to the expectation that the worst-case runoff heating events would occur during daylight hours. The analysis conducted for three rainfall events showed that the heat export from the commercial rooftop was roughly three times that of the residential rooftop, but only 30%-90% of the heat export from the concrete driveway. Potential heat export was significantly higher for the driveway than for either rooftop. In conclusion, the results of the data analysis and heat export simulations support the assumption that residential rooftops contribute very little heating to runoff from rainfall. Commercial rooftops may have a thermal impact on rainfall runoff because of their greater thermal storage capacity. An asphalt pavement, (road or driveway) is expected to have a greater thermal impact than a concrete pavement. Commercial rooftops in addition to asphalt and concrete pavements should be considered when the water temperatures of rainfall runoff from highly urbanized areas are estimated.
Hydrothermal Simulation of a Stormwater Detention Pond or Infiltration Basin
(St. Anthony Falls Laboratory, 2006-09) Herb, William R.; Weiss, Michael; Mohseni, Omid; Stefan, Heinz G.
A numerical simulation model has been developed to simulate the hydraulic and heat transfer properties of a stormwater detention pond. The model is dynamic (unsteady) and based on basic principles of hydraulics and heat transfer. It is driven by hourly climate and weather data. To calibrate and validate the pond model field data were collected on a commercial site (State Farm Insurance Company) in Woodbury, Minnesota. The relationship between pond inflow and outflow rates to precipitation was effectively calibrated using continuously recorded pond level. Algorithms developed for surface heat transfer in lakes were found to be applicable to the pond with some modification. A significant diurnal thermal stratification was simulated and measured in the pond which had 2.4m depth. Temperature differences from top to bottom were as high as 13oC during daytime hours. The outflowing water temperature was essentially equal to the pond surface temperature because the outlet was located near the pond surface. Outflow water temperatures were calculated with a RMSE of 1.4oC. Water clarity had little effect on the pond outflow temperatures but the pond bottom temperature was found to be highly sensitive to water clarity. For pond designs with outlet structures that take subsurface water, water clarity will introduce uncertainty to simulations of the pond temperature profile and the pond outlet temperature. Further work is required to consider other pond designs with alternate outlet structures, significant shading, and wind sheltering. Surface shading should include consideration of terrestrial vegetation (trees), emergent, submerged, and floating leaf aquatic vegetation, Algae need to be included in the water clarity. Wet ponds with subsurface outlet withdrawal and high surface shading from emergent or floating leaf plants may yield significantly lower outlet temperatures than typical wet pond designs.
Measuring the Effectiveness of Submersed Jets to Minimize Invasive Species Transport
(St. Anthony Falls Laboratory, 2023-11-01) Erickson, Andrew J.; Herb, William R.
MINUHET (Minnesota Urban Heat Export Tool) USER MANUAL
(St. Anthony Falls Laboratory, 2010-01) Herb, William R.; Janke, Ben; Mohseni, Omid; Stefan, Heinz G.
MINUHET (Minnesota Urban Heat Export Tool) is a tool used to simulate the flow of stormwater surface runoff and its associated heat content through a small watershed for a rainfall event or events of interest. The main output of MINUHET is a time series of flow rate and temperature at the outlet of the watershed, to enable prediction of thermal impact on receiving streams. MINUHET is event-based, i.e. it is designed primarily to simulate a single storm event. The MINUHET tool includes a database of observed and/or synthetic storm events that have the potential to produce high thermal loading in receiving streams.
MINUHET (Minnesota Urban Heat Export Tool): A software tool for the analysis of stream thermal loading by urban stormwater runoff
(St. Anthony Falls Laboratory, 2009-03) Herb, William R.; Janke, Ben; Mohseni, Omid; Stefan, Heinz G.
Urbanization affects the temperature of cold water resources, coldwater streams in particular. In Minnesota such streams are typically found in well-shaded watersheds and receive large groundwater inputs. They are ecologically significant because they support coldwater fisheries and other wildlife that would be unable to survive in warmer streams. The conversion of land from existing agricultural use or natural conditions poses a threat to these streams. Urban expansion usually requires removing crops and trees and replacing them with buildings, parking lots, roads, lawns, and parks. These changes affect shading, heat transfer, and hydrology within the watershed. Currently, there are few tools available to project to what extent stream temperatures are influenced by development in the watershed. This report describes a new simulation tool, MINUHET (Minnesota Urban Heat Export Tool). MINUHET is a tool used to simulate the flow of stormwater surface runoff and its associated heat content through a small watershed for one or several rainfall event of interest. The tool includes hydrologic and thermal models for surface runoff, natural and man-made drainage networks, and stormwater treatment ponds. The main output of MINUHET is a time series of flow rates and temperatures at the outlet of the watershed, to enable prediction of thermal impact on receiving streams. MINUHET is event-based, i.e. it is designed primarily to simulate a single storm event. The MINUHET tool includes a database of observed and/or synthetic storm events that have the potential to produce high thermal loading in receiving streams. Verification of MINUHET has been performed at both the component level and the system level. The surface temperature model was verified for a number of different impervious and pervious land surfaces for continuous, multi-month simulations of wet and dry conditions. The runoff model has been compared to other models, including a more complex kinematic wave model and a commercial runoff model (EPA-SWMM), and to observed runoff time series from a parking lot. The pond model component was used successfully to simulate several months of observed water level and temperature data for a wet detention pond in Woodbury, MN. The MINUHET tool has been applied to a 12 acre residential development in Plymouth, MN that was instrumented in 2005. A common application of MINUHET may be to compare the thermal loading of stormwater runoff from an area of land before and after development, to quantify possible increases in thermal loading due to development. MINUHET includes components for developed and undeveloped land parcels (sub-watersheds), pervious and impervious open channels, storm sewer systems, and stormwater ponds. MINUHET does not include a stream temperature model, so that while MINUHET can be used to simulate the heat loading to a stream, it cannot be used, by itself, to simulate the resulting change in stream temperature.
Permeable Pavement for Road Salt Reduction
(Minnesota Department of Transportation, 2020-06) Erickson, Andrew J.; Gulliver, John S.; Herb, William R.; Janke, Benjamin D.; Nguyen, Nam K.
Road salt and particularly sodium chloride is used for de-icing roadways during winter months in cold climates but can have a negative impact on the environment. This report describes research that investigated the use of permeable pavements that are not treated with road salt as an alternative to impermeable pavement surfaces that are treated with road salt. Various methods were used to quantify the snow and ice cover on impermeable and permeable pavements under near-identical but various environmental conditions. It must be noted, however, that impermeable pavements including the ones in this study are typically managed with road salt while permeable pavements are not. However, the following conclusions can be drawn from previous research and data collected during this project: 1) permeable pavements and the porous subbase beneath them function as thermal insulators, preventing heat transfer from the surface to below and vice versa; 2) permeable pavements that are clogged due to sediment accumulation or collapsed pores provide no benefit compared to impermeable pavement; 3) more sites with impermeable pavement had more friction than sites with permeable pavement; 4) more sites with impermeable pavement had less snow and/or ice cover than sites with permeable pavements; and 5) more sites with impermeable pavement had pooled water than sites with permeable pavements. This demonstrates the primary winter benefit of permeable pavements: meltwater can infiltrate through permeable pavements and prevent refreezing. Refreezing of meltwater on impermeable pavements creates dangerously slippery conditions which can be avoided with functional permeable pavements.
Projecting the Impact of Climate Change on Coldwater Stream Temperatures in Minnesota Using Equilibrium Tmperature models
(St. Anthony Falls Laboratory, 2010-09) Stefan, Heinz G.; Herb, William R.
Water temperature is a very important characteristic of aquatic habitats, particularly those supporting coldwater fish species such as trout [Eaton et al. 1995]. Stream temperature not only controls the survival of juvenile and adult coldwater fish, but also affects their reproduction and food sources such as macroinvertebrates [Durance and Ormerod 2007]. Hydrogeologic and climate settings constrain the existence of coldwater streams. In Minnesota, for example, trout streams are created by (1) karst springs in the southeast region of the state, near Rochester, 2) by cold wetlands in the northeast region of the state, near Duluth, and 3) by shallow groundwater aquifers in other regions of the state. The hydrological and climatological processes that maintain coldwater stream habitat vary between these regions, but involve a combination of cold water sources from groundwater or wetlands, riparian shading, and/or temperate climate. In other regions of the USA and the world, alpine settings with coldwater sources from snow or ice and cold mountain climate provide another important category of trout streams [Brown and Hannah 2007; Clark et al. 2001; Hari et al. 2006].
Stormwater Detention Pond Water Temperature Data Collection and Interpretation
(St. Anthony Falls Laboratory, 2011-05) Herb, William R.; Weiss, Michael P.; Stefan, Heinz G.
This report summarizes a field study that was conducted for the MPCA to collect the data necessary to support the formulation and validation of a temperature simulation model for urban stormwater detention ponds. The urban stormwater detention pond simulation model is included in the MINUHET (Minnesota Urban Heat Transfer) model that computes (simulates) runoff temperatures for typical residential and commercial watersheds. The model simulates single rainfall events or continuous periods of several months. The simulated runoff temperatures and volumes are used to estimate the heat loading from urban surface runoff to coldwater streams. To support these simulations, weather data and urban runoff temperature data had to be collected to serve as model inputs and to validate model outputs. In this report, a subset of the data collection effort is summarized. This report deals with stormwater detention ponds. The study was conducted in 2005 and 2006. Before a pond was chosen for detailed study, it was necessary to obtain an overview of typical stormwater detention ponds in an urban area. Eighteen stormwater detention ponds in Bloomington and Woodbury in the Twin Cities Metropolitan Area were documented, and are described in this report. Then a pond was selected for detailed instrumentation and data collection. That pond was on the former property of the State Farm Insurance Company Headquarters, near I94 and Radio Drive in Woodbury. The pond is a wet pond with an outflow structure and one major stormsewer inflow from two parking lots and the roof. Instrumentation was installed to measure and record weather data, temperature stratification data in the pond, surface inflow and outflow data, pavement temperature and pavement runoff temperature data. In support of another study on the fate of road salt in the Twin Cities area, additional data were collected to document salinity profiles in urban stormwater detention ponds. These data are also presented in this report.

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