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Results for “Flow Measurement and Instrumentation”

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USGS2004

USGS tethered ACP platforms: New design means more safety and accuracy

The US Geological Survey has developed an innovative tethered platform that supports an Acoustic Current Profiler (ACP) in making stream-flow measurements (use of the term ACP in this article refers to a class of instruments and not a specific brand name or model). The tethered platform reduces the hazards involved in conventional methods of stream-flow measurement. The use of the platform reduces or eliminates time spent by personnel in streams and boats or on bridges and cableway and stream-flow measurement accuracy is increased.

Hydro International↗

USGS2008

Advancing process‐based watershed hydrological research using near‐surface geophysics: A vision for, and review of, electrical and magnetic geophysical methods

We want to develop a dialogue between geophysicists and hydrologists interested in synergistically advancing process based watershed research. We identify recent advances in geophysical instrumentation, and provide a vision for the use of electrical and magnetic geophysical instrumentation in watershed scale hydrology. The focus of the paper is to identify instrumentation that could significantly advance this vision for geophysics and hydrology during the next 3–5 years. We acknowledge that this is one of a number of possible ways forward and seek only to offer a relatively narrow and achievable vision. The vision focuses on the measurement of geological structure and identification of flow paths using electrical and magnetic methods. The paper identifies instruments, provides examples of their use, and describes how synergy between measurement and modelling could be achieved. Of specific interest are the airborne systems that can cover large areas and are appropriate for watershed studies. Although airborne geophysics has been around for some time, only in the last few years have systems designed exclusively for hydrological applications begun to emerge. These systems, such as airborne electromagnetic (EM) and transient electromagnetic (TEM), could revolutionize hydrogeological interpretations. Our vision centers on developing nested and cross scale electrical and magnetic measurements that can be used to construct a three‐dimensional (3D) electrical or magnetic model of the subsurface in watersheds. The methodological framework assumes a ‘top down’ approach using airborne methods to identify the large scale, dominant architecture of the subsurface. We recognize that the integration of geophysical measurement methods, and data, into watershed process characterization and modelling can only be achieved through dialogue. Especially, through the development of partnerships between geophysicists and hydrologists, partnerships that explore how the application of geophysics can answer critical hydrological science questions, and conversely provide an understanding of the limitations of geophysical measurements and interpretation.

Hydrological Processes↗

USGS1984

Measurement of discharge using tracers

The development of fluorescent dyes and fluorometers that can measure these dyes at very low concentrations has made dye-dilution methods practical for measuring discharge. These methods are particularly useful for determining discharge under certain flow conditions that are unfavorable for current meter measurements. These include small streams, canals, and pipes where: Turbulence is excessive for current meter measurement but conducive to good mixing. Moving rocks and debris are damaging to any instruments placed in the flow. Cross-sectional areas or velocities are indeterminant or changing. There are some unsteady flows such as exist with storm-runoff events on small streams. The flow is physically inaccessible or unsafe. From a practical standpoint, such measurements are limited primarily to small streams due to excessively long channel mixing lengths required of larger streams. Very good accuracy can be obtained provided: Adequate mixing length and time are allowed. Careful field and laboratory techniques are employed. Dye losses are not significant. This manual describes the slug-injection and constant-rate injection methods of performing tracer-dilution measurements. Emphasis is on the use of fluorescent dyes as tracers and the equipment, field methods, and Laboratory procedures for performing such measurements. The tracer-velocity method is also briefly discussed.

Open-File Report↗

USGS2022

Seismometer records of ground tilt induced by debris flows

A change in surface loading causes the Earth’s surface to deform. Mass movements, such as debris flows, can cause a tilt large enough to be recorded by nearby instruments, but the signal is strongly dependent on the mass loading and subsurface parameters. Specifically designed sensors for such measurements (tiltmeters) are cumbersome to install. Alternatively, broadband seismometers record translational motion and also tilt signals, often at periods of tens to hundreds of seconds. Their horizontal components are thereby the most sensitive to tilt. In this study, we show how to obtain tilt caused by the passing by of debris flows from seismic measurements recorded within tens of meters of the flow and investigate the usefulness of this signal for flow characterization. We investigate the problem on three scales (1) large‐scale laboratory experiments at the U.S. Geological Survey debris‐flow flume, where broadband seismometers and tiltmeters were installed for six 8 – 10    m 3 "> 8 – 10 m 3 experiments, (2) the Illgraben torrent in Switzerland, one of the most active mass wasting sites in the European Alps, where a broadband seismometer placed within a few meters of the channel recorded 15 debris‐flow events with volumes up to 10 5    m 3 "> 10 5 m 3 ⁠ , and (3) Volcán de Fuego, Guatemala, where a broadband seismometer recorded two lahars. We investigate how the tilt signals compare to debris‐flow parameters such as mean normal stresses, usually measured by expensive force plates, and debris‐flow height. We model the elastic ground deformation as the response of an elastic half‐space to a moving surface load. In addition, we use the model with some simplifications to determine the maximum debris‐flow heights of Volcán de Fuego events, where no force plate measurements are available. Finally, we address how and under what assumptions the relatively affordable and straightforward tilt measurements may be utilized to infer debris‐flow parameters, as opposed to force plates and other complicated instrument setups.

Oregon↗

USGS2021

Dynamic selection of exposure time for turbulent flow measurements

The selection of optimum sampling configurations to measure the aspects of turbulent flow of water depends on the variable being measured, the applied measurement technique, the degree of environmental noise, and flow characteristics in and near the sampling location. This work presents a method to dynamically select the exposure time (SET) during the flow-velocity measurement at each sampling location on the basis of the moving block bootstrap (MBB) technique. The MBB enables near real-time estimation of the confidence intervals and, subsequently, the COV for turbulence parameters. The dynamic SET method has been tested in this work using time series of synthetic turbulent flow-velocity signals. This method was implemented using actual flow-velocity signals recorded with acoustic Doppler velocity (ADVs) instruments and acoustic Doppler current profilers (ADCPs). The results obtained from the implementation of the dynamic SET method show that the sampling time to achieve a defined uncertainty threshold is not the same for different turbulence parameters. Consequently, using the dynamic SET method, the exposure time can be optimized to obtain the turbulence parameters with the required uncertainty level. The dynamic SET method can be implemented in the instrument’s data logger to dynamically select the exposure time during flow measurements for a given uncertainty of the required turbulence parameter.

Journal of Hydraulic Engineering↗

USGS2020

Cottonwoods, water, and people-Integrating analysis of tree rings with observations of elders from the Eastern Shoshone and Northern Arapaho Tribes of the Wind River Reservation, Wyoming

We assessed the history of flow and riparian ecosystem change along the Wind River using cottonwood tree-ring data, streamgage records, historical temperature and precipitation data, drought indices, and local observations and Traditional Ecological Knowledge from elders of the Eastern Shoshone and Northern Arapaho Tribes of the Wind River Reservation, Wyoming. This assessment identified impacts that have occurred to riparian resources of concern to the Tribes, which will assist in prioritizing drought planning efforts. Impacts included reduced abundance, reduced regeneration, and increased mortality in cottonwoods ( Populus deltoides and P. angustifolia ); an increase in invasive species, especially Russian olive ( Elaeagnus angustifolia ), that are gradually replacing cottonwoods and other native woody plants; decreased abundance of native and culturally important plants; reduced abundance of culturally important fish; reduced volume and changes to the timing of flows; and changes in river course. This assessment documented the biophysical and social factors that have contributed to riparian ecosystem change and to reduced water availability and flows, including agricultural diversion, drought, and fire. Cottonwoods along the Wind River are as much as 300 years old. By relating tree-ring width to recorded streamflows, we were able to reconstruct streamflows confidently back to the 1850s and speculatively back to the mid-1700s. Extending the historical record of streamflows allows for a more-complete understanding of hydroclimatic variability and provides a foundation for developing preparedness and response strategies for drought management. Ring width of cottonwood trees at the Boysen Site was more strongly correlated to river flow than to local precipitation or temperature, indicating that growth of trees is controlled more by montane snowmelt than by local weather. Therefore, tree rings are a better indicator of water supply than of the local conditions controlling water demand. The extended flow record from tree rings revealed the occurrence of a major period of low flow from 1870 to 1910 that was not evident in the shorter instrumental records of flow and weather. Information from tree rings, streamflow measurements, drought indices, and elder observations all suggest that the early 2000s drought was the most severe, sustained drought in the last century. Our results illustrate how drought is experienced in different ways across locations and sectors, which underscores the importance of using multiple indicators for drought management. These results will contribute to ongoing assessment, monitoring, and planning efforts at the Wind River Reservation.

Wyoming↗

USGS1985

Measurement of discharge using tracers

The development of fluorescent dyes and fluorometers that can measure these dyes at very low concentrations has made dye-dilution methods practical for measuring discharge. These methods are particularly useful for determining discharge under certain flow conditions that are unfavorable for current meter measurements. These include small streams, canals, and pipes where 1. Turbulence is excessive for current-meter measurement but conducive to good mixing. 2. Moving rocks and debris may damage instruments placed in the flow. 3. Cross-sectional areas or velocities are indeterminate or changing. 4. The flow is unsteady, such as the flow that exists with storm-runoff events on small streams and urban storm-sewer systems. 5. The flow is physically inaccessible or unsafe. From a practical standpoint, such methods are limited primarily to small streams, because of the excessively long channel-mixing lengths required for larger streams. Very good accuracy can be obtained provided that 1. Adequate mixing length and time are allowed. 2. Careful field and laboratory techniques are used. 3. Dye losses are not significant. This manual describes the slug-injection and constant-rate injection methods of performing tracer-dilution measurements. Emphasis is on the use of fluorescent dyes as tracers and the equipment, field methods, and laboratory procedures for performing such measurements. The tracer-velocity method is also briefly discussed.

Techniques of Water-Resources Investigations↗

USGS2021

Accuracy of flowmeters measuring horizontal flow in fractured-rock simulators

Laboratory evaluations of flowmeter response to flow in fractured-rock simulators are needed to improve understanding of data collected in field settings. The ability of flowmeters to accurately measure the velocity and direction of water flowing between parallel plates was used as a surrogate for instrument response in fractured-rock aquifers. A colloidal borescope flowmeter and a heat-pulse flowmeter were deployed in a fractured rock simulator with 4-inch and 6-inch inner-diameter, uncased wells with 0.39- and 1.0-inch fracture apertures and groundwater velocities from 35 to 975 ft/d. The colloidal borescope measurements and applied velocities were positively correlated in all wells and apertures (the coefficient of determination [ r 2 ] = 0.61–0.89) and most accurately measured direction at higher velocities. The mean directional error in colloidal borescope measurements was less than 17° in 6-inch wells and 31° in the 4-inch wells at velocities between 92 and 958 ft/d. Heat-pulse flowmeter measurements were 0.001 to 0.004 times less than applied rates and may indicate that water was moving around rather than through the instrument's integrated packer. The mean directional error of heat-pulse flowmeter measurements were about 18 and 42° in the 0.39- and 1.0-inch fractures, respectively, for groundwater velocities within the manufacturer's suggested range of application (0.5–100 ft/d). Measurements made at vertical increments and fracture positions in the well using the colloidal borescope indicate that laminar flow occurs within the central 50% of the fracture but measurements above or below are likely affected by eddy currents.

Groundwater Monitoring & Remediation↗

USGS1997

Measuring flood discharge in unstable stream channels using ground-penetrating radar

Field experiments were conducted to test the ability of ground-penetrating radar (GPR) to measure stream-channel cross sections at high flows without the necessity of placing instruments in the water. Experiments were conducted at four U.S. Geological Survey gaging stations in southwest Washington State. With the GPR antenna suspended above the water surface from a bridge or cableway, traverses were made across stream channels to collect radar profile plots of the streambed. Subsequent measurements of water depth were made using conventional depth-measuring equipment (weight and tape) and were used to calculate radar signal velocities. Other streamflow-parameter data were collected to examine their relation to radar signal velocity and to clarity of streambed definition. These initial tests indicate that GPR is capable of producing a reasonably accurate (±20%) stream-channel profile and discharge far more quickly than conventional stream-gaging procedures, while avoiding the problems and hazards associated with placing instruments in the water.

Geology↗

USGS2021

Preconditioning by sediment accumulation can produce powerful turbidity currents without major external triggers

Turbidity currents dominate sediment transfer into the deep ocean, and can damage critical seabed infrastructure. It is commonly inferred that powerful turbidity currents are triggered by major external events, such as storms, river floods, or earthquakes. However, basic models for turbidity current triggering remain poorly tested, with few studies accurately recording precise flow timing. Here, we analyse the most detailed series of measurements yet made of powerful (up to 7.2 m s −1 ) turbidity currents, within Monterey Canyon, offshore California. During 18-months of instrument deployment, fourteen turbidity currents were directly monitored. No consistent triggering mechanism was observed, though flows did cluster around enhanced seasonal sediment supply. We compare turbidity current timing at Monterey Canyon (a sandy canyon-head fed by longshore drift) to the only other systems where numerous (>10-100) flows have been measured precisely via direct monitoring; the Squamish Delta (a sandy fjord-head delta), and the Congo Canyon (connected to the mud-dominated mouth of the Congo River). A common seasonal pattern emerges, leading to a new model for preconditioning and triggering of turbidity currents initiating through slope failure in areas of sediment accumulation, such as canyon heads or river mouths. In this model, rapid or sustained sediment supply alone can produce elevated pore pressures, which may persist, thereby predisposing slopes to fail. Once preconditioned, a range of minor external perturbations, such as moderate storm-waves, result in local pore pressure variation, and thus become effective triggers. Major external triggers are therefore not always a prerequisite for triggering of powerful turbidity currents.

Earth and Planetary Science Letters↗

USGS1964

Apparatus and techniques for measuring bedload

The need for accurate determinations of the total sediment discharge of particles of bedload size has prompted this investigation of available and possible measuring apparatus and procedures. The accuracy of measurements of sediment discharge made with trap-type samplers is affected by the variability of sampler efficiency, by the oscillatory variation of bedload discharge, and by sampler placement. Equations that were developed for determining total discharge from measured bedioad discharge and measured suspended-sediment discharge are simplest if the bedload apparatus measures only the true bedload. Early bedload samplers are generally unsatisfactory. Recently developed or suggested apparatus include various improved samplers of the pressure-difference type, a pumping sampler, a magnetic sampler, acoustical instruments that measure the magnitude of the sound of particle collisions, an ultrasonic bedload sampler designed to measure and integrate electronically the concentration and velocity, and a tiltmeter designed to measure the total sediment discharge from the ground tilt that results from the passage of flow. All the pressure-difference samplers are improvements over early samplers, but none are void of the inherent shortcomings of trap-type apparatus; probably the Sphinx (Dutch) and VUV (Hungarian) samplers are the most satisfactory. The acoustical instruments are capable of measuring only the relative discharge. The ultrasonic sampler and the tiltmeter are not adequate without further development. Some new possible apparatus and means for measuring or aiding in measuring bedload discharge are small pit samplers, ultrasonic sounders, pressure transducers, and photography. A small pit sampler for measuring bedload discharge was designed to provide self-placement and portability ; however, its practicability and efficiency are undetermined. Exploratory films show that by using slowmotion photography the discharge of particles larger than about pea size can be determined provided the flow is clear; however, photography generally is not practical. Ultrasonic sounders provide continuous and accurate data on bed configuration and dune movement for use in equations that were developed for computing the bedload discharge. Computations with the equations indicate that the interpretation of the sounding data needs further study. Pressure transducers placed beneath the bed surface possibly can be used to provide information on dune movement; however, their installation would be difficult. The time required for collecting data on bed configuration and dune movement throughout a cross section could be substantially reduced by using several transducers simultaneously in conjunction with an ultrasonic sounder. A modified ultrasonic sounder that provides information on the shape and velocity of large particles and a method for determining the discharge of such particles were proposed; the method seems most feasible for particles of high sphericity.

Water Supply Paper↗

USGS2012

Characterizing a December 2005 density current event in the Chicago River, Chicago, Illinois

During the winter months, the Chicago River in Chicago, Illinois is subject to bi-directional flows, and density currents are thought to be responsible for these flow variations. This paper presents detailed field measurements using three acoustic Doppler current profiler instruments and simultaneous water-quality measurements made during December 2005. Observations indicate that the formation of density currents within the Chicago River and density differences are mostly due to salinity differences between the North Branch and the main stem of the Chicago River, whereas temperature difference does not appreciably affect the creation of density currents. Sources of higher water temperature, conductivity, and salinity values should be addressed in future studies. ?? 2007 ASCE.

Conference Paper↗

USGS2022

Evaluation of select velocity measurement techniques for estimating discharge in small streams across the United States

Multiple instruments and methods exist for collecting discrete streamflow measurements in small streams with low flows, defined here as less than 5.7 m 3 /s (200 ft3/s). Included in the available methods are low-cost approaches that are infrequently used, in part, because their uncertainty is not well known. In this work, we evaluated the accuracy and suitability of three low-cost velocity measurement methods (surface float [SF], velocity head rod [VR], and rising body [RB]) and three conventional current meters (acoustic Doppler velocimeter, and mechanical Price type AA and Price Pygmy meters) relative to discharge calculated from stable artificial hydraulic controls. A total of 231 measurements were made by 20 individuals during 88 site visits to 24 sites in eight states. Accuracies were assessed for all methods and precision was evaluated for the low-cost methods. The median percent error was below 5% for conventional methods, and below 20% for the low-cost methods. The SF was the most accurate (median absolute percent error 14%) and precise (mean percent precision of 11%) low-cost method. The RB and VR, respectively, had 15% and 20% median absolute percent error and 29% and 12% mean percent precision. Results suggest that low-cost methods, when used appropriately, can be used to estimate discharge data under low flow conditions when measurements with conventional methods are not feasible and the associated accuracies meet end-user measurement objectives.

continental United States↗

USGS2006

Drainage effects on the transient, near-surface hydrologic response of a steep hillslope to rainfall: Implications for slope stability, Edmonds, Washington, USA

Shallow landslides on steep (>25??) hillsides along Puget Sound have resulted in occasional loss of life and costly damage to property during intense or prolonged rainfall. As part of a larger project to assess landslide hazards in the Seattle area, the U.S. Geological Survey instrumented two coastal bluff sites in 2001 to observe the subsurface hydrologic response to rainfall. The instrumentation at one of these sites, near Edmonds, Washington, consists of two rain gauges, two water-content probes that measure volumetric water content at eight depths between 0.2 and 2.0 m, and two tensiometer nests that measure soil-water suction at six depths ranging from 0.2 to 1.5m. Measurements from these instruments are used to test one- and two-dimensional numerical models of infiltration and groundwater flow. Capillary-rise tests, performed in the laboratory on soil sample from the Edmonds site, are used to define the soil hydraulic properties for the wetting process. The field observations of water content and suction show an apparent effect of porosity variation with depth on the hydraulic response to rainfall. Using a range of physical properties consistent with our laboratory and field measurements, we perform sensitivity analyses to investigate the effects of variation in physical and hydraulic properties of the soil on rainfall infiltration, pore-pressure response, and, hence, slope stability. For a two-layer-system in which the hydraulic conductivity of the upper layer is at least 10 times greater than the conductivity of the lower layer, and the infiltration rate is greater than the conductivity of the lower layer, a perched water table forms above the layer boundary potentially destabilizing the upper layer of soil. Two-dimensional modeling results indicate that the addition of a simple trench drain to the same two-layer slope has differing effects on the hydraulic response depending on the initial pressure head conditions. For slope-parallel flow conditions, pressure head is significantly reduced near the drain; however, for transient, vertical infiltration in a partially saturated soil, conditions consistent with those observed during monitoring at the Edmonds site, the drain decreases the thickness of a perched water table by a small amount.

Natural Hazards and Earth System Sciences↗

USGS2025

Monitoring lava lake fluctuations and crater refilling with continuous laser rangefinders

The U.S. Geological Survey’s Hawaiian Volcano Observatory (HVO) has developed a new method to continuously monitor lava lake elevations. Since 2018, HVO has stationed a laser rangefinder on Kīlauea’s caldera rim. The instrument automatically measures lava lake elevation each second, with centimeter accuracy. A stream of elevation data flows to HVO’s database and public website, contributing a valuable channel to HVO’s volcano monitoring network. The data display is intuitive for users, providing essential information with a new level of clarity. HVO has used this method to track Kīlauea’s changing lava lake elevations over a series of eruptions, and the time series data show several volcanic processes: crater refilling, gas pistoning, lava lake surface behavior, and endogenous crater floor uplift. This technique is versatile, nimble, and easy to use. Continuous laser rangefinders may also prove useful for tracking lava lakes elsewhere, and for monitoring other hazards such as growing lava domes and debris flows.

Hawaii↗

USGS1979

Instrumentation of urban hydrology monitoring sites in southeast Florida

An instrumentation system developed and built in laboratories of the U.S. Geological Survey, Reston, Va., has been used since 1974 to collect synchronized rainfall, runoff, and water-quality data from urban basins. A number of field modifications were made to adapt the system to local hydrologic conditions and for collection of data on about 350 rainstorms at four sites in south Florida. The instrumentation system measures rainfall at three sites, records two pressure or water-level readings for flow computations, and collects and refrigerates up to 24 water samples and rainfall-quality samples. Rainfall and runoff data are recorded every 36 seconds on a six-channel analog recorder so that all variables are time-synchronous. Flow in the storm sewer is computed from pressure measurements in a U-shaped venturi-type constriction or, when the constriction is not used, from water levels. (Kosco-USGS)

Florida↗

USGS2004

Evaluating a Radar-Based, Non Contact Streamflow Measurement System in the San Joaquin River at Vernalis, California

Accurate measurement of flow in the San Joaquin River at Vernalis, California, is vital to a wide range of Federal and State agencies, environmental interests, and water contractors. The U.S. Geological Survey uses a conventional stage-discharge rating technique to determine flows at Vernalis. Since the flood of January 1997, the channel has scoured and filled as much as 20 feet in some sections near the measurement site resulting in an unstable stage-discharge rating. In response to recent advances in measurement techniques and the need for more accurate measurement methods, the Geological Survey has undertaken a technology demonstration project to develop and deploy a radar-based streamflow measuring system on the bank of the San Joaquin River at Vernalis, California. The proposed flow-measurement system consists of a ground-penetrating radar system for mapping channel geometries, a microwave radar system for measuring surface velocities, and other necessary infrastructure. Cross-section information derived from ground penetrating radar provided depths similar to those measured by other instruments during the study. Likewise, surface-velocity patterns and magnitudes measured by the pulsed Doppler radar system are consistent with near surface current measurements derived from acoustic velocity instruments. Since the ratio of surface velocity to mean velocity falls to within a small range of theoretical value, using surface velocity as an index velocity to compute river discharge is feasable. Ultimately, the non-contact radar system may be used to make continuous, near-real-time flow measurements during high and medium flows. This report documents the data collected between April 14, 2002 and May 17, 2002 for the purposes of testing this radar based system. Further analyses of the data collected during this field effort will lead to further development and improvement of the system.

Open-File Report↗

USGS1997

Characterization of stormwater runoff from the Naval Air Station and Naval Wepons Industrial Reserve Plant, Dallas, Texas, 1994-96

The characterization of stormwater runoff from the Naval Air Station (NAS) and the Naval Weapons Industrial Reserve Plant (NWIRP), Dallas, Texas, is necessary to determine if runoff from the facilities is contributing to off-site contamination of surface waters, A network of five fixed sites and four grab sites was established to collect stormwater-runoff samples from a substantial part of the drainage area of each facility. Fixed sites were instrumented to measure and store precipitation, stage, discharge, and runoff-volume data and to collect flow-weighted composite samples during a storm. Grab and composite samples were collected for six storms at each of the five fixed sites from October 1994 to March 1996. The grab samples were analyzed for about 100 properties and constituents including specific conductance, pH, water temperature, bacteria, trace elements, oil and grease, total phenols, and volatile organic compounds. The composite samples were analyzed for about 220 properties and constituents including specific conductance, pH, chemical oxygen demand, biochemical oxygen demand, major ions, suspended and dissolved solids, nutrients, trace elements, total organic carbon, volatile organic compounds, semivolatile organic compounds, and organochlorine and organophosphorus pesticides. Grab samples were collected for two storms (September 18,1995, and October 2,1995) at each of the four grab sites. The grab samples were analyzed for about 80 constituents including specific conductance, pH, water temperature, trace elements, and volatile organic compounds. Composite samples were collected for two of the six storms sampled at the fixed sites and analyzed for aquatic toxicity. Fathead minnow growth and survival toxicity tests and water flea reproduction and survival toxicity tests were done. Median event-mean concentrations computed for 12 selected constituents in samples from NAS and NWIRP fixed sites were compared to median event-mean concentrations for residential, commercial, industrial, and highway land uses within the Dallas-Fort Worth area computed from data collected for the National Pollutant Discharge Elimination System program. NAS and NWIRP median event-mean concentrations also were compared to those for residential and commercial land uses from the Nationwide Urban Runoff Program.

Open-File Report↗