History and Development of the NRCS Lag Time Equation1

Abstract: Many of the hydrologic methods that are used in engineering practice today resulted from the Spring Flood of 1936, which blanketed the Northeastern portion of the United States. Because of the flood damage that was caused by this rainfall‐snowmelt event, many federal agencies including the U.S. Army Corp of Engineers and the Soil Conservation Service (SCS) implemented the hydrologic theories that were available in the literature at this time and developed hydrologic procedures for design flow estimation. Sherman had recently published his unit hydrograph theory in 1932, and later in 1938 Snyder, who had been charged by the Water Resource Council to develop a synthetic unit hydrograph, published his famous paper. The SCS unit hydrograph theory was developed by Victor Mockus in the late 1950s. Most if not all of the theories at that time reported the rainfall‐runoff process for floods as a surface phenomenon, and as such those theories all required some type of a timing parameter to estimate watershed response time. This article documents the development of the SCS lag equation.     

Corn residue level and manure application timing effects on phosphorus losses in runoff

Growing interest in corn (Zea mays L.) silage utilization on Wisconsin dairy farms may have implications for nutrient losses from agricultural lands. Increasing the silage cutting height will increase residue cover and could reduce off-site migration of sediments and associated constituents compared with conventional silage harvesting. We examined the effects of residue level and manure application timing on phosphorus (P) losses in runoff from no-till corn. Treatments included conventional corn grain (G) and silage (SL; 10- to 15-cm cutting height) and nonconventional, high-cut (60-65 cm) silage (SH) subjected to different manure application regimes: no manure (N) or surface application in fall (F) or spring (S). Simulated rainfall (76 mm h(-1); 1 h) was applied in spring and fall for two years (2002-2003), runoff from 2.0- x 1.5-m plots was collected, and subsamples were analyzed for dissolved reactive phosphorus (DRP), total phosphorus (TP), and P mass distribution in four particle size classes. Total P and DRP loads were inversely related to percent residue cover, but both TP and DRP concentrations were unaffected by residue level. Manure application increased DRP concentrations in spring runoff by two to five times but did not significantly affect DRP loads, since higher concentrations were offset by lower runoff volumes. Spring manure application reduced TP loads in spring runoff by 77 to 90% compared with plots receiving no manure, with the extent of reductions being greatest at the lower residue levels (<24%). The TP concentration in sediments increased as particle size decreased. Manure application increased the TP concentration of the 0- to 2-microm fraction by 79 to 125%, but elevated the 2- to 10- and 10- to 50-microm fractions to a lesser extent. Recent manure additions were most influential in enriching transported sediments with P. By itself, higher residue cover achieved by high-cutting silage was often insufficient to lower P losses; however, the combination of manure application and higher residue levels significantly reduced P losses from corn fields harvested for silage.     

Evolution of hybrid functional imaging in bioelectromagnetics research

The field of bioelectromagnetics, consisting of the study of the interaction between electromagnetic fields and biological systems, has been rapidly expanding in the recent years. One important factor that contributes importantly to the development of this field is the continuing advances in technology allowing researchers to investigate different endpoints, or to more precisely measure changes, if any. Hybrid functional imaging is a rapidly maturing field that opens new, important horizons for bioelectromagnetics research. Indeed, unraveling the interaction mechanisms of electromagnetic fields on biological systems (with an emphasis on the brain) requires a monitoring of electrical, functional, and metabolic activity of living tissue at different temporal and spatial scales. Individual tools (e.g., electroencephalography, EEG; functional magnetic resonance imaging, fMRI) are limited in their ability to detect the effects of electromagnetic interaction at specific temporal and spatial scales, so combining these imaging methods offers a unique opportunity to provide a more comprehensive view of effects in living tissue. In this paper, we will present the different imaging techniques that are available to bioelectromagnetics researchers, including their capabilities and how they are complemented by simultaneous hybrid imaging. Future possibilities of hybrid imaging technologies are discussed.     

HOUSEHOLD WATER USE: TECHNOLOGICAL SHIFTS AND CONSERVATION IMPLICATIONS1

ABSTRACT: A study was undertaken to determine the effect of water intensive appliances or activities on household water consumption. Activities included in the study were use of the washing machine, dishwasher, swimming pool, and lawn watering. In the majority of cases these activities increased per capita consumption and were statistically significant. Households included in the study were not familiar with water saving devices available in the retail market. Even if tehse appliances were purchased, private economic benefits to the household would be low due to the inexpensive water charges levied. However, aggregate community benefits could be large if new well drilling cost or increase in storage facilities could be avoided. In order to avoid these increased costs, regulation or subsidy programs may be the most efficient policy alternatives available to the communities. Subsidies and regulation could potentially decrease water use and offer alternatives to increasing the water supply.     

Multiplicative sensitivity analysis and its role in development of simulation models

A procedure of extended sensitivity analysis for simulation models is developed which is applicable to the situation in which input uncertainties are specified in a multiplicative (rather than an additive) way. This type of specification usually occurs when error estimates are large relative to the parameter values. The input parameter errors are assumed to have log-normal distributions and the basis for this assumption is explained along with the advantages it provides. The new procedure, multiplicative sensitivity analysis, is developed for the purposes of internal model validation and identification of priorities for specific experimental and theoretical studies needed for a particular system being modelled. The applicability of the procedure in the very early stages of a research program is its main advantage and further expands the rôle of simulation models.     

Contribution of In‐Channel Processes to Sediment Yield of an Urbanizing Watershed1

Abstract: A study was conducted between September 2003 and September 2006 to obtain baseline sediment inventories and monitor sediment transport and storage along a 3.7 km length of the channel of Valley Creek within Valley Forge National Historical Park, Pennsylvania. Valley Creek is a tributary of the Schuylkill River and drains an urbanizing 60.6 km² watershed that currently has 18% impervious land cover. Numerous field methods were employed to measure the suspended sediment yield, longitudinal profile, cross‐sections, banklines, and particle size distribution of the streambed. Suspended sediment yield for the watershed was measured at a USGS gage located just upstream of the park boundary between July 2004 and July 2005, the period corresponding to field surveys of bank erosion and channel change. The estimated suspended sediment yield of 95.7 t/km²/year is representative of a year with unusually high discharge, including a storm event that produced a peak of 78 m³/s, the second highest discharge on record for the USGS gage. Based on the median annual streamflow for the 24 years of record at the USGS gage from 1983 to 2006, the median annual sediment yield is estimated to be closer to 34 t/km²/year, considerably lower than median and mean values for other sites within the region. The mass of silt, clay, and fine sand derived from bank erosion along the 3.7 km study reach during the field survey period accounts for an estimated 2,340 t, equivalent to about 43% of the suspended sediment load. The mass of fine sediment stored in the bed along the study reach was estimated at 1,500 t, with about 330 t of net erosion during the study period. Although bank erosion appears to be a potentially dominant source of sediment by comparison with annual suspended sediment load, bed sediment storage and potential for remobilization is of the same order of magnitude as the mass of sediment derived from bank erosion.     

Prediction of the Vertical Profile of Ozone Based on Ground-Level Ozone Observations and Cloud Cover

Abstract

A number of statistical techniques have been used to develop models to predict high-elevation ozone (O₃) concentrations for each discrete hour of day as a function of elevation based on ground-level O₃ observations. The analyses evaluated the effect of exclusion/inclusion of cloud cover as a variable. It was found that a simple model, using the current maximum ground-level O₃ concentration and no effect of cloud cover provided a reasonable prediction of the vertical profile of O₃, based on data analyzed from O₃ sites located in North Carolina and Tennessee. The simple model provided an approach that estimates the concentration of O₃ as a function of elevation (up to 1800 m) based on the statistical results with a ±13.5 ppb prediction error, an R² of 0.56, and an index of agreement, d ₁, of 0.66. The inclusion of cloud cover resulted in a slight improvement in the model over the simple regression model. The developed models, which consist of two matrices of 24 equations (one for each hour of day for clear to partly cloudy conditions and one for cloudy conditions), can be used to estimate the vertical O₃ profile based on the inputs of the current day’s 1-hr maximum ground-level O₃ concentration and the level of cloud cover.     

A Study of Catalyst Support Systems for Fume-Abatement of Hydrocarbon Solvents

In a stainless steel pilot plant system, operating with combined thermal incineration and catalytic oxidation, studies have been made of the influence of catalyst-support geometry on abatement efficiency. Catalyst supports tested were ceramic spherical pellets, metal foils, and ceramic honeycomb structures, all with precious metal catalyst. Data obtained cover a range of space velocities from 30,000 to 175,000 scf/hr— cu ft bed and a range of catalytic reactor temperatures from 150 to 450°C. Results show that optimum fume-abatement performance is obtained by combining incineration and catalytic oxidation and that catalyst support geometry has a significant effect on performance.     

Penetration and Duration of Oxidant Air Pollution in the South Coast Air Basin of California

On June 18, 19, and 20, 1970, two aircraft, a rawinsonde, two pibal stations, and four ground stations provided simultaneous samples of total oxidant, temperature, and winds up to 8000 ft in an area extending from Santa Monica, Calif., east to Redlands and north across the San Bernardino Mountains. It was shown that photochemical oxidant formed in the marine layer is vented up the slopes and over the crest of the San Bernardino Mountains during the day. Layers of high oxidant concentrations were detected above the inversion base, suggesting that some pollution is vented up the slopes and subsequently advected back to the south. The diurnal changes in the temperature inversion also contribute to the high concentration found above the inversion base. These processes result in multi-layers of pollution. The study suggests that oxidant air pollution is transported up to 80 mi to forested mountains, where severe damage to conifer species has been documented.     

Nitrous oxide emissions from a Northern Great Plains soil as influenced by nitrogen management and cropping systems

Field measurements of N2O emissions from soils are limited for cropping systems in the semiarid northern Great Plains (NGP). The objectives were to develop N2O emission-time profiles for cropping systems in the semiarid NGP, define important periods of loss, determine the impact of best management practices on N2O losses, and estimate direct N fertilizer-induced emissions (FIE). No-till (NT) wheat (Triticum Aestivum L.)-fallow, wheat-wheat, and wheat-pea (Pisum sativum), and conventional till (CT) wheat-fallow, all with three N regimes (200 and 100 kg N ha(-1) available N, unfertilized control); plus a perennial grass-alfalfa (Medicago sativa L.) system were sampled over 2 yr using vented chambers. Cumulative 2-yr N2O emissions were modest in contrast to reports from more humid regions. Greatest N2O flux activity occurred following urea-N fertilization (10-wk) and during freeze-thaw cycles. Together these periods comprised up to 84% of the 2-yr total. Nitrification was probably the dominant process responsible for N2O emissions during the post-N fertilization period, while denitrification was more important during freeze-thaw cycles. Cumulative 2-yr N2O-N losses from fertilized regimes were greater for wheat-wheat (1.31 kg N ha(-1)) than wheat-fallow (CT and NT) (0.48 kg N ha(-1)), and wheat-pea (0.71 kg N ha(-1)) due to an additional N fertilization event. Cumulative losses from unfertilized cropping systems were not different from perennial grass-alfalfa (0.28 kg N ha(-1)). Tillage did not affect N2O losses for the wheat-fallow systems. Mean FIE level was equivalent to 0.26% of applied N, and considerably below the Intergovernmental Panel on Climate Change mean default value (1.25%).