A seasonal monitoring program of flexible pavement performance has been performed in Tennessee since 1996, in which the water content of the subgrade is measured by Time Domain Reflectometry (TDR) probes. Five-segment probes were chosen to increase the number of measurements and volume of soil monitored. The variations of water content measured in the subgrade and the base course closely follow the temperature trends. This finding suggests the significance of temperature effects on TDR measurement. A laboratory calibration program was thus carried out to study the temperature effects on TDR measurement of volumetric water content. Temperature effects on TDR measurement are related to the energy of the signal. After correcting for temperature effects, the field TDR measurements of volumetric water content appear to track a seasonal variation.

Preferential recharge from agricultural production fields can lead to agrochemical contamination of groundwater due to short-circuiting of the soil matrix. This research determines the relative amounts of preferential and matrix flow recharge from a no-till agricultural production field. The conservative tracer potassium bromide was surface applied to a 0.37 ha bermed field plot at a rate of 900 kg ha-1 as bromide. The site was instrumented to monitor precipitation and runoff from the bermed field plot. Three years after the bromide application, twenty-one 3.65 m continuous soil cores were collected from the bermed plot and analyzed for bromide. Based solely on the shape of the bromide profiles, most of the 21 soil cores showed no apparent preferential flow. However, up to 83% of the infiltrated bromide mass was absent from individual soil cores, presumably due to preferential flow. Using a mass balance approach, we estimated that 58% of the recharge was due to preferential flow and 42% was due to matrix flow.

A comprehensive instrumentation system was installed at four sites across the state of Tennessee to monitor long-term seasonal changes in subgrade water content. This paper summarizes the instrumentation and evaluates each of the monitoring methods. The instrumentation included a complete weather station, time domain reflectometry probes, temperature sensors in the pavement and subgrade, free-drainage pan lysimeters, and resistivity probes. The paper describes problems encountered, how they were resolved, the value of the data obtained, and provides recommendations based on the lessons learned from the 5-years of data collection.

Estimated daily reference crop evapotranspiration (ETo) is normally used to determine the water requirement ofcrops using the crop factor method. Many ETo estimation methods have been developed for different types of climatic data,and the accuracy of these methods varies with climatic conditions. In this study, pair-wise comparisons were made betweendaily ETo estimated from eight different ETo equations and ETo measured by lysimeter to provide information helpful inselecting an appropriate ETo equation for the Cumberland Plateau located in the humid Southeast United States. Based onthe standard error of the estimate (Syx), the relationship between the estimated and measured ETo was the best using theFAO-56 Penman-Monteith equation (coefficient of determination (r2) = 0.91, Syx = 0.31 mm d-1, and a coefficient ofefficiency (E) = 0.87), followed by the Penman (1948) equation (r2 = 0.91, Syx = 0.34 mm d-1, and E = 0.88), and Turcsequation (r2 = 0.90, Syx = 0.36 mm d-1, and E = 0.88). The FAO-24 Penman and Priestly-Taylor methods overestimated ETo,while the Makkink equation underestimated ETo. The results for the Hargreaves-Samani equation showed low correlationwith lysimeter ETo data (r2 = 0.51, Syx = 0.68 mm d-1, and E = 0.20), while those for the Kimberly Penman were reasonable(r2 = 0.87, Syx = 0.40 mm d-1, and E = 0.87). These results support the adoption of the FAO-56 Penman-Monteith equationfor the climatological conditions occurring in the humid Southeast. However, Turcs equation may be an attractive alternativeto the more complex Penman-Monteith method. The Turc method requires fewer input parameters, i.e., mean air temperatureand solar irradiance data only.

Accurate knowledge of nitrate distribution in the soil under fertigation through drip-irrigation systems is fundamentally important for system design and management. The determination of nitrate distribution through modeling represents a highly complex nonlinear problem that includes adsorption, transformation, convection, and dispersion. For this reason, an alternative methodology is proposed, which combines artificial neural networks (ANN) and laboratory experiments. Seventeen experiments with apparent discharge rates varying from 0.6 to 7.8 l/h, the apparent cylindrical applied volume from 6 to 15 l, and the input concentration from 100 to 700 mg/l were conducted to provide a database for establishing the ANN architecture. The model input parameters were initial soil water content, initial nitrate concentration in the soil, discharge rate, input concentration of fertilizer (NH 4 NO 3 ), applied volume, and final soil water content. The model output was nitrate concentration in the soil after fertigation. A total of 298 vectors were used to train the ANN model, and 212 independent vectors were used to test the model. Results of the test show a good correspondence with a determination coefficient ( r 2 ) of 0.83 between the model-estimated nitrate concentration in the soil and laboratory-measured nitrate concentration in the soil. These results show that the optimized ANN models are reasonably accurate and can provide an easy and efficient means of estimating nitrate distribution in the soil under fertigation through drip-irrigation systems.

Although strongly adsorbing ions are relatively immobile within porous media, preferentialflow and adsorption to mobile colloids can enhance their transport. There is limited knowledgeregarding the role of preferential flow and colloidal transport on adsorbing ions. The goal of thisresearch is to determine the influence of preferential flow paths and colloids on transportation ofadsorbing ions. The movement of a conservative tracer within soil by preferential flow has beenstudied in previous research at a west Tennessee field plot and results demonstrate rapid transportof the tracer. Eight soil monoliths with a diameter of 0.3 m and a length of 1.0 m were excavated andcollected in PVC pipes from the Ames Plantation, near Grand Junction, Tennessee. The monolithswere transported to the laboratory where a column experiment was performed to determine thetransport rate of an adsorbing and non-adsorbing ion. Four monoliths were treated with poultry litter,and the other four monoliths were treated with inorganic fertilizer. Fertilizer was applied atcongruence to the recommended Nitrogen rate of 168 kg ha-1. Water spiked bromide as KBr, whichbehaves as a conservative tracer, was applied daily to the surface of all monoliths at a constantconcentration of 20 ppm d-1. Fiberglass wicks sampled water moving through the matrix, and waterdripping from the base of the column, indicative of preferential flow, was collected using a brassnipple. Concentrations of total phosphorus, inorganic phosphorus, organic phosphorus, and bromidewere measured. The transport of P from preferential flow and matrix flow of a monolith werecompared by constructing breakthrough curves for the brass nipple and fiberglass wicks. A portionof the effluent samples were filtered with 0.45 and/or 0.1 mm nylon filters to reveal the role colloidsplay in ionic transport. P concentrations were relatively higher in the free water compared to thematrix water, indicative that when preferential paths are present P adsorption is decreased.Monoliths with early detection of Br also had elevated P concentrations. Leachate samples from thefiberglass wicks had lower Br concentrations than leachate samples from the brass nipple.Comparisons between the inorganic and organic fertilizer effects on P transport are inconclusive atthis time. Additional studies on the monoliths are ongoing.

Water quality samples were collected from four subwatersheds based on the followingland uses: rural (11.66 km2), agricultural (19.43 km2), mixed (12.95 km2), and urban (16.32 km2).These subwatersheds were located in a 60.36-km2 watershed in the upper reaches of SweetwaterCreek in East Tennessee. The samples were collected on a semi-discrete flow dependent basis and asweekly grab samples. A stage-discharge curve was developed for each subwatershed collection site.The stream stage was monitored using a level sensor and a datalogger. Based on the stream level, theflow volume was calculated and accumulated in the datalogger until a preset value was reached,which triggered a pump sampler. Weekly, at each subwatershed site, the flow dependent sampleswere collected from the pump sampler along with a single grab sample from the stream. The sampleswere analyzed for each the following: chloride, nitrite, nitrate, phosphate, sulfate, and total suspendedsolids. Two five-day periods of this data are used to evaluate the effectiveness of the samplingtechniques to represent water quality in these different land uses. Levels of nitrite and phosphatewere below analytical detection limits at all sampling sites, except the Urban sub watershed site, andwere not used in the evaluation. Total mass loadings were calculated using the following: thirtyminuteaverage flow data and corresponding automated flow dependent sample analysis;concentrations from the analysis of a grab sample collected at the beginning of the time period andthirty-minute flow data; and the grab sample concentrations and the stream flow rate when the samplewas collected and extrapolated to represent the five-day time period. Comparison of the calculatedtotal mass loadings of the constituents during the five-day period without rainfall show a grab sample,with or without supporting flow measurements were representative. However, the mass loadingcalculations for the five-day period with rainfall show evidence of first-flush of constituents. Theconcentrations of the constituents remain the same or increase as flow rate increases during a rainfallevent. This dramatically increases the total mass loading of the constituents during a rainfall event.A grab sample with a single corresponding flow measurement cannot be extrapolated to representmass loading during a rainfall event. The results of grab sampling to represent mass loading can beimproved if stream flow rate is monitored, and the data used to calculate to mass loading.

An integrated approach of biological and chemical analyses was used to determine theimpact of land use on stream health in four sub-watersheds along Sweetwater Creek in southeastTennessee. By monitoring the mass loading of water quality constituents from flow proportionalsamples and determining an Index of Biotic Integrity (IBI) and an Ephemoroptera, Plecoptera, andTrichoptera (EPT) taxa count, a comparison was made of the impact of land-use on water quality.The Sweetwater Creek watershed, which covers 6,216 ha, was subdivided into four sub-watershedsbased on the following land uses: Agricultural (1,943 ha), Rural (1,166 ha), Mixed (1,295 ha), andUrban (1,632 ha). A stage-discharge curve was developed for each sub-watershed sampling site.The stream stage was monitored using a water level sensor connected to a datalogger. Based onthe stream level, the flow volume was calculated and accumulated in the datalogger until a presetvalue was reached which triggered a pump sampler. Laboratory analyses from these flowproportional samples along with corresponding stream discharge values allowed the calculation ofmass loading of the stream. With these data, direct comparisons were made between the subwatershedsfor the following: chloride, nitrate, sulfate, and total suspended solids (TSS). While manychemical measures of water constituents are frequently used to quantify water quality, a biologicalhealth assessment, using indicator species, may also be used to determine water quality. Theresults of the mass loading analyses showed the Rural, Mixed, and Agricultural sub-watersheds weresimilar. In the Mixed sub-watershed, TSS values decreased, which was probably due to streamshape, which caused the water velocity to decrease resulting in sediment deposition. Mass loadingfrom the Urban sub-watershed was as much as ten times greater for each of the constituents duringthe storm event evaluated. The Index of Biotic Integrity (IBI) value, which is based on the presenceor absence of fish species, was very poor (22) for the Urban stream reach; the Mixed and Ruralstream reaches were rated poor (32), and the Agricultural stream reach was rated poor/fair (38).The Ephemeroptera, Plecoptera, and Trichoptera (EPT) ratings, which are based on the count oftaxa of these three orders of macroinvertebrates that are known to be sensitive to pollution, weresimilar to the IBI ratings; the Urban stream reach yielded the lowest counts, The Mixed andAgricultural stream reaches had slightly higher counts than the Urban reach, and the Rural streamreach had the highest EPT taxa count for each of the three sampling events. A habitat assessmentanalysis of the stream reaches supported the conclusions from the IBI index and EPT taxa count.

A procedure to aid the decision-making process for delineating site-specific management units forirrigation was developed. The procedure consists of evaluating the management units through a site-specificirrigation schedule and a model that simulates the effects of water deficit on crop yield. Areas of the field arefirst grouped into minimum management units, which have the least amount of AWHC variability. Themanagement units are then evaluated through an economic response model. The framework is general andportable for different soil and weather conditions. The procedure was tested in a case study for tomatoproduction to evaluate the different field layouts, from the maximum number of minimum management units(site-specific irrigation) to the whole field (uniform irrigation). The optimum layout was site-specific layout 4 withthree management units and the highest average annual net return ($17,381/ha $7,614/ha for a 16.24 hafield).

Ground-penetrating radar (GPR) technology has supplied vital assistance in criminal investigations. However, law enforcement personnel desire further developments such that the technology is rapidly deployable, and that it provides both a simple user interface and sophisticated target identification. To assist in the development of target identification algorithms, our efforts involve gathering background GPR data for the various site conditions and circumstances that often typify clandestine burials. For this study, forensic anthropologists established shallow-grave plots at The University of Tennessee Anthropological Research Facility (ARF) that are specific to GPR research. These plots contain donated human cadavers lying in various configurations and depths, surrounded by assorted construction material and backfill debris. We scanned the plots using two GPR technologies: (1) a multi-frequency synthetic-aperture FM-CW radar [Formula: see text] (GPR-X) developed by the U.S. Department of Energy’s Special Technologies Laboratory (STL), Bechtel Nevada (Koppenjan et al., 2000), and (2) a commercial pulse radar (SIR-20) manufactured by Geophysical Survey Systems, Inc. (400 and [Formula: see text]) (GSSI). The sweep-frequency data show the large biological mass decomposing within the torso as encircled “hot spots.” The [Formula: see text] pulse radar exhibit major horizontal reflectors above the body, with shadow reflectors (horizontal multiples) occurring beneath the body at [Formula: see text] depth. The [Formula: see text] antenna was able to discern the grave walls and folded tarp covering the lower body. Under these moist, clay-rich conditions, the [Formula: see text] antenna was able to penetrate slightly beyond [Formula: see text] beneath the concrete layer. However, neither system was able to penetrate beyond a one meter depth in the moist, clay-rich soil (fine, mixed, thermic Typic-Paleudalf). Example scans from each system are provided, along with a discussion of the survey protocol and general performance.

Identifying the subsurface paths by which water moves within the vadose zone is difficult. Limited scientific data are available that detail agrochemical migration for the innumerable combinations of soil and hydrological factors, and for the wide array of agricultural production practices. We are using electromagnetic induction (EMI) sensing in a unique timeelapsed imaging format to target high-, moderate-, and low-risk moisture movement patterns. Our research on loess-over-alluvium soils demonstrates that subsurface water movement is highly variable and site-specific. Often a small soil volume conducts a large water flow volume. Site-specific soil structural features usually cause this concentrated flow. Water moves rapidly offsite from certain areas of fields, while little or no lateral subsurface flow occurs in other areas. We are targeting those field areas that have high potential for offsite movement of agrochemicals using Geographic Information Systems (GIS) and Differential Global Positioning Systems (DGPS) technologies. This paper gives an overview of our dynamic imaging process for temporal and spatial mapping of soil conductivity for visualizing near-surface water movement.

In response to public awareness of foodborne pathogens due to recent outbreaks of illness, a study was conducted on the incidence of Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella species on a dairy farm in middle Tennessee. Sampling locations included water samples from up- and down-stream in a creek running through the farm, free stall bedding, silage, separator liquids, separator solids, pumped liquid from a holding pond, feed, and bulk tank milk. Three samples were taken monthly at each location for 12 months. These samples were tested to determine the incidence of pathogens on the dairy farm and to identify seasonal trends in pathogen presence. No E. coli O157:H7 was found in any of the samples. L. monocytogenes was present most often in the pumped holding pond liquid and the separator liquid, with each producing positives in 31% of the samples. The bedding and silage samples were negative for L. monocytogenes for the entire testing period. A possible seasonal trend was identified in L. monocytogenes, with more positive samples collected during cooler months. Salmonella were ubiquitous in pumped liquid, with 34 (94%) of the 36 samples testing positive; separator liquid and separator solid samples returned Salmonella positives on 72% and 81%, respectively. The downstream samples yielded 27% positives, whereas the upstream samples identified 42% Salmonella positive. After testing was completed, locations associated with waste, such as the manure solids separator and the holding pond, were identified as potential control points for L. monocytogenes and Salmonella.