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Item 1:27 Scale Physical Model of Spillway Air Ramp Alternatives for the 15 de Septiembre Project(1993-07) Ramanathan, V.; Voigt, Richard L. Jr.Item An Acoustic Study of Gaseous Micro-Bubbles In Boundary Layers and Propeller Wakes(St. Anthony Falls Hydraulic Laboratory, 1962-12) Ripken, John F.; Killen, John M.This report deals with exploratory tests to measure the nature of the free gas which occurs in natural water due to the dynamic disturbance of a ship. Acoustic attenuation measurements serve to show that micro gas bubbles are evolved from dissolved gases by the shear dynamics of a boundary layer and that the rate of evolution increases as some function of the intensity and duration of the disturbance and of the pressure, viscosity, and gas content of the water. The tests were conducted in the Laboratory, in large scale simulations of a ship's boundary layer and propeller, and in wakes of actual ship propeller's. These exploratory tests indicate the need for more extensive tests in sea water under a wide variety of naval operating conditions. Such tests are necessary to a better determination of the role that these bubbles play in cavitation and acoustic detection problems.Item Addendum To Final Memorandum Of July 1963: Calibration Of Spillway With Low Crest Blocks(St. Anthony Falls Hydraulic Laboratory, 1966-01) Anderson, Alvin G.This addendum reports the results of calibration tests on the partially completed Angat spillway. The study was based upon a memorandum by W. A. Waldorf, Harza Engineering Company, dated September 20, 1965.Item Air Entrainment in Flowing Water(St. Anthony Falls Hydraulic Laboratory, 1949-08) Lamb, Owen P.The physical entrainment of a gas by a liquid and the flow of gas-liquid mixtures are phenomena commonly encountered in engineering practice, but avoided or arbitrarily compensated for in theoretical considerations and in design analysis. The progress toward a satisfactory explanation of these phenomena has been hampered by a lack of accurate experimental observations of entrained flows and by the complexity of the theoretical analysis when certain of the physical forces can no longer be neglected.Item Air-Water Mixture Flow Through Orfices, Bends, and other Fittings in a Horizontal Pipe(St. Anthony Falls Hydraulic Laboratory, 1960-09) Silberman, EdwardIn planning piping systems for flow of gas-liquid mixtures, it is necessary to know something about the pressure and the pressure changes along the line. The pressure changes may be considered partly frictional and partly nonfrictional. Both of these mechanisms are active in mixture flows in straight, uniform pipes, and in fittings with gradual changes in cross section and/or alignment such as diffusers and bends. In fittings with abrupt changes in cross section, such as orifices, frictional losses are relatively small and pressure changes are largely the result of changes in kinetic energy and momentum. Furthermore, the flow pattern (that is, whether the flow be bubble, plug, annular, etc.) is dependent on the local pressure, other factors being constant, and it may be desirable to mow something about the flow pattern for use in heat transfer calculations, for example, and even for use in calculations for pressure drop in some fittings.Item 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.Item Analysis and Simulation of Mixing of Stratified Layers or Reservoirs by Air Bubble Plumes(St. Anthony Falls Hydraulic Laboratory, 1990-12) Zic, Kresimir; Stefan, Heinz G.The goal of the research presented in this report is to analyze, understand, and simulate the flow field induced by a bubble plume in a lake or reservoir. This is useful and necessary for the design of lake or reservoir aeration and destratification projects. Three mathematical models were developed and laboratory experiments were performed. Experiments similar to the ones presented here are not available in the literature but were necessary to understand the governing physical processes and to verify the mathematical models. What makes these experiments unique, in comparison with other bubble plume measurements is the description of the entire flow field (not just the flow in vicinity of the bubble plume), the inclusion of stratified ambient water, and the evaluation of destrati:fication over time. The first. model developed is a modified version of a dynamic 1-D mathematical model originally formulated by Goossens[1979]. The improved model is based on the research described here and is linked to a general dynamic lake model MINLAKE. It is a tool useful for lake restoration projects, particularly for evaluation of different restoration techniques. The second model is also an integral model of a bubble plume. The flow field induced by an air bubble plume in stratified ambient water is presented in the general context of mixing mechanics of water jets and plumes. The third model is a 2-D numerical model that gives insight into the subregions of the flow field. The 2-D model solves the Reynolds' equations by using the buoyancy-extended version of the k-e model as a closure of the turbulent quantities. The effect of the bubbles in the fluid flow is modeled by imposing internal forces in the region where the air bubbles are present. A discussion of lake aeration as an oxygen transfer technique is beyond the scope of the research described herein.Item Analysis of a Hydroacoustic Gravity Flow Facility(St. Anthony Falls Laboratory, 1984-09) Arndt, Roger E.; Wetzel, Joseph M.; Bintz, David W.; Ripken, John F.Two preliminary designs of a hydroacoustic gravity flow facility have been developed for a Ship Silencing Laboratory, DTNSRDC, by Dr. George F. Wis1icenus. It was desired to attain a test section velocity of 60 fps for a 90 sec time period. As the facility will be used for acoustic measurements, cavitation-free flow is a necessity. After a test run has been completed, the water is returned by a pump in a separate line back to the head tank. To ma~imize usage of the facility, the recycling time between runs should be kept short. As part of the overall development program, the Laboratory has been asked to carry out some preliminary calculations on the proposed designs to further establish feasibility and to independently evaluate the designs. The calculations included an estimate of head loss in the system and an elementary transient analysis. An alternate configuration also has been suggested for consideration.Item 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.Item Analysis of Flow through Sturgeon Lake and Backwater Channels of Mississippi River Pool No. 3 Near Red Wing, Minnesota(St. Anthony Falls Hydraulic Laboratory, 1977-04) Stefan, Heinz; Anderson, KeithFlow rates through Sturgeon Lake and backwater channels of the Mississippi River in the vicinity of the Prairie Island Nuclear power Generating Plant are determined as a function of total river flow and of wind direction and wind velocity, particularly for low flow conditions. The analysis is made in order to determine; (a) how much of the Sturgeon Lake flow is drawn into the cooling water intake of the plant, and (b) by how much plant effluent cooling water or blow down water is diluted by sturgeon Lake effluent before entering the Mississippi River. A channel network analysis including effects of wind stress on the water surface in addition to bed shear stress and local (minor) energy losses was made to provide the required information. Forty-three channel and channel segments were used to describe the entire system. The Sturgeon Lake/North Lake system was studied before the complete analysis was made. In the absence of wind, flow through Sturgeon Lake amounted to about 22 percent of total river flow. At low plant withdrawal rates and at zero wind, the flow through the backwater channel in front of the plant outlet (channel 42) was about 10 percent of total river flow. Winds from 5 to 30 mph had a very noticeable effect on flows through Sturgeon Lake, particularly when total river flows were less than 10,000 cfs. The analysis was made without consideration of stratification effects near the plant intake and outlet.Item Analysis of Stormwater Runoff Best Management Practices in Miller Creek, Duluth, MN(2021-01) Herb, WilliamItem 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.Item Analysis of the effect of stormwater runoff volume regulations on thermal loading to the Vermillion River(St. Anthony Falls Laboratory, 2008-09) Herb, WilliamResidential and commercial development dramatically alters the surface and groundwater hydrology of watersheds. Increasing areas of impervious surfaces can lead to higher peak stream flows and reduced baseflow, which both can lead to degradation of fish habitat. In addition, thermal pollution from surface runoff is increasing recognized as an additional mechanism for fish habitat degradation in coldwater stream systems. Stormwater best management practices (BMPs) such as infiltration ponds, rain gardens, and swales are often used to reduce stormwater surface runoff rates and volumes, and to increase infiltration and groundwater recharge. Wet detention ponds used to limit runoff flow rates and reduce sediment loads are not likely to reduce thermal loading, since there is no reliable mechanism for volume or temperature reduction. Infiltration practices that capture all of smaller storms and initial portion of larger storms are very likely to significantly reduce thermal loading, since the warmest surface runoff typically happens during low volume storms and the initial portions of larger storms. To predict changes in thermal loading to streams due to land use changes, a simulation model of runoff temperature is currently being developed as part of a research project that SAFL is conducting for the Minnesota Pollution Control Agency (“Development and Implementation of a Tool to Predict and Assess the Impact of Stormwater Runoff on Trout Streams”). The current version of the tool, MINUHET (MINnesota Urban Heat Export Tool), has components for simulating runoff volume and temperature for mixed land use sub-divisions, routing of runoff flow and heat through both conventional storm sewer systems and pervious channels, and for simulating wet ponds and infiltration ponds. Thus, MINUHET has the capability to quantify the reduction in thermal loading due to the addition of infiltration practices.Item Analysis of the Elfuel Coal Drying Facility(St. Anthony Falls Hydraulic Laboratory, 1990-10) Rindels, Alan J.; Gulliver, John S.; Wetzel, Joseph M.; Voller, VaughanThe ELFUEL coal drying facility is designed to utilize the high heat transfer characteristics of a moving packed bed counter-current heat exchanger to efficiently "hot-water dry" lignite coal. Past research into hot water drying of lignite indicates the process is energy inefficient, requiring greater energy input than what can be extracted from the treated lignite. The novel approach of the ELFUEL coal drying facility utilizes the high heat transfer characteristics of a counter-current solid/liquid packed bed to efficiently add and later remove heat to and from descending coal in a pressurized cylindrical vessel. This approach uses raw coal continuously descending in a vertical cylindrical refractory. Coal, upon entering the refractory at the top, gradually heats to process temperatures near the location of hot water injection through contact with hot water flowing upward. Below the point of hot water injection, cool water is forced upward past the descending coal to trap or conserve heat or energy in the system. Sufficient energy is conserved by this design to economically hot-water dry lignite coal. Design of a counter-current energy efficient system which adds and then removes heat has not been reported in the literature. Wonchala and Wynnyckyj (1986) reports counter-current packed bed processes are common in the metallurgical industries. Some important example include the iron blast furnace and iron-ore pelletizing shaft furnace which are very useful since they exhibit a very high potential heat transfer efficiency. However, the metallurgical counter-current gas-solid heat exchangers have not been found to be energy efficient due to channeling of hot gases (Wonchala and Wynnyckyj, 1986). It was the purpose of this study to determine whether the ELFUEL coal drying facility outlined in Minnesota Power's proposal "ELFUEL Demonstration of Low-Rank Coals" to the U. S. Department of Energy, Clean Coal Technology, Round #3 will perform as described and meet the objectives of the process, the economical hot-water drying of lignite coal.Item Analysis of Vermillion River Stream Flow Data (Dakota and Scott Counties, Minnesota)(St. Anthony Falls Laboratory, 2008-07) Herb, William; Stefan, HeinzAs part of an effort to characterize the response of the Vermillion River to surface runoff, the flow records from seven gaging stations were analyzed to determine the data quality, typical low flows, and the contribution of major tributaries to the total flow. The flow record from the U.S. Geological Survey gaging station at Empire appears to give the most reliable flow data and has the longest record (33 years). An effort by the Minnesota Department of Natural Resources (MNDNR) to recalibrate other Vermillion River flow gaging stations appears to have resulted in self-consistent data for 2007 flows in the main stem and at tributary stations. Although many of the stream gaging stations examined in this study have flow records of up to eight years, flow data prior to 2007 have to be used with caution. To select a representative summer low flow for a stream temperature analysis, the 33 year record at the USGS station at Empire was analyzed to determine 7Q2, and 7Q10 low flows, and monthly median and mean flows. The monthly and 7Q2 flows are representative of typical flow conditions, while the 7Q10 flow is an extreme low flow condition. Analyses were made both with and without the flow contribution of the Empire WWTP (wastewater treatment plant), to asses both pre- and post-2007 conditions. For a July/August composite average, the mean, median, 7Q2, and 7Q10 flows at the USGS station are 68.0, 43.4, 28.6, and 12.5 cfs, respectively, without the WWTP effluent.Item 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, HeinzExisting 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.Item 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.Item Analytical Assessment of the Proposed Raw Water Intake Pollutant Diversion Structure(St. Anthony Falls Laboratory, 1997-12) Voigt, Richard L. Jr.; Kostic, SvetlanaThe St. Anthony Falls Laboratory was contracted by Short ElBott Hendrickson to perform an assessment of potential sedimentation related issues associated with the installation of a flow diversion structure at the Minneapolis Water Works raw water intake. The Minneapolis Water Works raw water intake withdraws water from the Mississippi river at approximately river mile 858.5, Following treatment, the water becomes the primary water supply for Minneapolis and some suburbs. To continue to operate following a contaminant spill upstream of the intake requires the installation of a diversion structure which can effectively divert non~water soluble contaminants past the intake structure. The project involved the review of key riverine related issues including: • The potential for siltation to occur in the region downstream of the diversion structure between the island and intake. • The potential for erosion of the far bank and the island caused by channel constriction. • The potential for de~pening of the primary channel due to the constriction. • The potential for sediment and contaminants to enter the downstream end of the channel. • The general stability of the island. In addition to these issues, several secondary operational related issues were also reviewed.Item Annual Stream Runoff and Climate in Minnesota’s River Basins(St. Anthony Falls Laboratory, 2010-09) Vandegrift, Todd R.; Stefan, Heinz G.Stream flows recorded by the USGS from 1946 to 2005 at 42 gauging stations in the five major river basins of Minnesota and tributaries from neighboring states were analyzed and related to associated climate data. Goals of the study were (1) to determine the strength of the relationships between annual and seasonal runoff and climatic variables in these river basins, (2) to make comparisons between the river basins of Minnesota, and (3) to determine trends in stream flows over time. Climatic variables were air temperature, precipitation, the Palmer Drought Severity Index (PDSI), and the Palmer Hydrological Drought Index (PHDI); the latter are common indices of soil moisture. Water year averages showed stronger correlations than calendar year averages. Precipitation was a good predictor of stream flow, but the PDSI was the best predictor and slightly better than PHDI when linear regressions at the annual timescale were used. With an exponential regression PDSI gave a significantly better fit to runoff data than PHDI. Five-year running averages made precipitation almost as good a predictor of stream flow (runoff) as PDSI. A seasonal time scale analysis revealed a logical stronger dependence of stream flow on precipitation during summer and fall than during the winter and spring, but all relationships for seasonal averages were weaker than for annual (water year) averages. Dependence of stream runoff on PDSI did not vary significantly by season. On a monthly timescale the strength of correlation between precipitation and runoff dropped off significantly, while PDSI was still a decent predictor in all months but the spring. Annual stream flow in the Upper Mississippi River Basin, including the Minnesota River Basin, had the strongest dependence on precipitation and PDSI. The Red River of the North Basin showed lower than average dependence on precipitation and average dependence on PDSI. The Rainy River Basin and the Lake Superior Basin showed the weakest dependence of annual stream flow on precipitation and PDSI. The relationship between stream flow and precipitation can be expressed most easily by an annual average runoff coefficient, i.e. the ratio of runoff to precipitation in a year. Runoff coefficients vary significantly across the state of Minnesota, from more than 0.4 in the northeast to less than 0.1 in the northwest. Trends in runoff coefficients were estimated from averages for 20-year periods from 1926-1945 to 1986-2005, although data for 1926-1945 were sparse. According to our analysis, runoff coefficients in some of the major river basins of Minnesota have increased significantly during the last 40 years. The Lake Superior and Rainy River Basins have high and invariant characteristic runoff coefficients around 0.35. The Red River Basin has the lowest characteristic runoff coefficient at ~0.14 but its value has consistently increased from the beginning of the record. The Mississippi Headwaters Basin characteristic runoff coefficient has increased to ~0.24. The Minnesota River Basin runoff coefficient (from the Minnesota River at Jordan, MN station) has also increased significantly and consistently to 0.19. The largest increases in runoff coefficients were found in the Red River and the Minnesota River Basins, the two basins with the lowest runoff coefficients; runoff coefficients in some tributary or sub-watersheds have doubled. In the Lake Superior and Rainy River Basins, and in the St. Croix River watershed, little change in runoff coefficients was found. Overall runoff coefficients drop significantly from east to west in Minnesota. This distribution does not seem to have changed over time. Increases in runoff coefficients over time have been highest in the west, and lowest in the east of Minnesota. One can hypothesize that changes in stream flow in Minnesota’s west are mainly due to land use changes that have lead to faster and easier surface runoff from the land since the beginning of European settlement. An explanation based on climatological factors can, however, also be offered. Precipitation has increased in all of the river basins of Minnesota over the time period of 1926 to 2005, but the largest changes have occurred in the south and west and little change in the northeast of Minnesota. Changes in total annual runoff (in/yr) between 1946 - 1965 and 1986 – 2005 increased at 38 of 42 stream gaging stations analyzed. Only 4 gaging stations, 3 in the Lake Superior and Rainy River Basins showed decreases, with all being less than 3%. The largest increases in average annual runoff were at 19 gaging stations in the Red River and Minnesota River Basins; at 17 of these, increases were from 60% to 132%, and at the remaining two stations the increases were 19% and 20%. The southern Minnesota watersheds with the largest increases in runoff also had the largest increases in precipitation. Overall, stream flow, expresses as annual runoff (in/yr), has increased since the beginning of stream gaging in Minnesota and the Upper Midwest, although periods of substantially lowered stream flows have occurred, e.g. in the drought period of the 1930s. Not only has the runoff (cm/yr) increased, but runoff coefficients, i.e. the ratio of runoff to precipitation, have also increased. When viewed as a percent change of annual runoff, the largest stream flow changes have occurred in the western part and the lowest in the eastern part of Minnesota. Increases in absolute values of annual runoff, percent of runoff, and runoff coefficients have been quantified in this study.Item Application of a Runoff Temperature Model (MINUHET) to a Residential Development in Plymouth, MN(St. Anthony Falls Laboratory, 2007-06) Janke, Ben; Herb, William; Mohseni, Omid; Stefan, HeinzThe MINUHET (MINnesota Urban Heat Export Tool) model is a simulation tool used to route heat and storm water through a sub-watershed for a rainfall event or events of interest. The model includes components for developed land uses, undeveloped or vegetated land uses, pervious and impervious open channels, storm sewer systems, and storm water ponds. As a case study, the model has been applied to a 12.5 acre housing development in Plymouth, MN. The process of identifying necessary data is outlined, as well as a general strategy for organizing the input data and setting up the model for this particular watershed. A catch basin at the outlet of the development was instrumented for flow and temperature, and data were collected at the site from August 25, 2005 to October 1, 2005. The model was run for three rainfall events, and a comparison was made between observed and simulated flow rate and flow temperature at the development outlet. Overall, the model performed well. The RMSE for flow was 42.0 L/s, 10.4 L/s, and 14.3 L/s for the three events respectively, and the corresponding RMSE in storm water runoff temperature was 1.6 °C, 1.2 °C, and 1.9 °C. Observed and simulated volumeaveraged mean runoff temperature differed by less than 1.5 ºC for all three events. Total volume of runoff was predicted with reasonable accuracy by the model, especially for the first two events. Heat export, which is a measure of the heat content of the runoff above a certain reference temperature (in this case 16.0 °C), was accurately predicted for the second and third events. The model was found to be highly sensitive to saturated hydraulic conductivity and rainfall temperature (dew point temperature): volume of runoff from the pervious areas varied considerably with changes in hydraulic conductivity, and runoff temperature often tended toward dew point temperature, especially in the absence of large atmospheric or ground heat fluxes (e.g., late at night or early in the morning). This suggests that special care should be taken in selection of soil properties, and that all climate data should be collected as near to the study site as possible to improve the accuracy of runoff temperature estimation.