Joseph L. Taraba

SIMULATION OF DAILY AND MONTHLY STREAM DISCHARGE FROM SMALL WATERSHEDS USING THE SWAT MODEL

The Soil and Water Assessment Tool (SWAT) was evaluated and parameter sensitivities were determined while modeling daily streamflows in a small central Kentucky watershed over a two-year period. Streamflow data from 1996 were used to calibrate the model and streamflow data from 1995 were used for evaluation. The model adequately predicted the trends in daily streamflow during this period although Nash-Sutcliffe R 2 values were –0.04 and 0.19 for 1995 and 1996, respectively. The model poorly predicted the timing of some peak flow values and recession rates during the last half of 1995. Excluding daily peak flow values from August to December improved the daily R 2 to 0.15, which was similar to the 1996 daily R 2 value. The Nash-Sutcliffe R 2 for monthly total flows were 0.58 for 1995 and 0.89 for 1996 which were similar to values found in the literature. Since very little information was available on the sensitivity of the SWAT model to various inputs, a sensitivity analysis/calibration procedure was designed to evaluate parameters that were thought to influence stream discharge predictions. These parameters included, drainage area, slope length, channel length, saturated hydraulic conductivity, and available water capacity. Minimization of the average absolute deviation between observed and simulated streamflows identified optimum values/ranges for each parameter. Saturated hydraulic conductivity, alpha baseflow factor, drainage area, channel length, and channel width were the most sensitive parameters in modeling the karst influenced watershed. The sensitivity analysis process confirmed die trace studies in the karst watershed that a much larger area contributes to streamflow than can be described by the topographic boundaries. Overall, the results indicate that the SWAT model can be an effective tool for describing monthly runoff from small watersheds in central Kentucky that have developed on karst hydrology however calibration data are necessary to account for solution channels draining into or out of the topographic watershed.

Statistical procedures for evaluating daily and monthly hydrologic model predictions

The overall study objective was to evaluate the applicability of different qualitative and quantitative methods for comparing daily and monthly SWAT computer model hydrologic streamflow predictions to observed data, and to recommend statistical methods for use in future model evaluations. Statistical methods were tested using daily streamflows and monthly equivalent runoff depths. The statistical techniques included linear regression, Nash-Sutcliffe efficiency, nonparametric tests, t-test, objective functions, autocorrelation, and cross-correlation. None of the methods specifically applied to the non-normal distribution and dependence between data points for the daily predicted and observed data. Of the tested methods, median objective functions, sign test, autocorrelation, and cross-correlation were most applicable for the daily data. The robust coefficient of determination (CD*) and robust modeling efficiency (EF*) objective functions were the preferred methods for daily model results due to the ease of comparing these values with a fixed ideal reference value of one. Predicted and observed monthly totals were more normally distributed, and there was less dependence between individual monthly totals than was observed for the corresponding predicted and observed daily values. More statistical methods were available for comparing SWAT model-predicted and observed monthly totals. The 1995 monthly SWAT model predictions and observed data had a regression Rr 2 of 0.70, a Nash-Sutcliffe efficiency of 0.41, and the t-test failed to reject the equal data means hypothesis. The Nash-Sutcliffe coefficient and the Rr 2 coefficient were the preferred methods for monthly results due to the ability to compare these coefficients to a set ideal value of one.

Streambank Erosion Associated with Grazing Practices in the Humid Region

The effects of cattle grazing on stream stability have been well documented for the western portion of the U.S., but are lacking for the east. Stream and riparian damage resulting from grazing can include alterations in watershed hydrology, changes to stream morphology, soil compaction and erosion, destruction of vegetation, and water quality impairments. However, few studies have examined the successes of best management practices (BMPs) for mitigating these effects. The objective of this project was to assess the ability of two common BMPs to reduce streambank erosion along a central Kentucky stream. The project site consisted of two replications of three treatments: (1) an alternate water source and a fenced riparian area to exclude cattle from the stream except at a 3.7 m wide stream ford, (2) an alternate water source with free stream access, and (3) free stream access without an alternate water source (i.e., control). Fifty permanent cross-sections were established throughout the project site. Each cross-section was surveyed monthly from April 2002 until November 2003. Results from the project indicated that the incorporation of an alternate water source and/or fenced riparian area did not significantly alter stream cross-sectional area over the treatment reaches. Rather than exhibiting a global effect, cattle activity resulted in streambank erosion in localized areas. As for the riparian exclosures, changes in cross-sectional area varied by location, indicating that localized site differences influenced the processes of aggradation and/or erosion. Hence, riparian recovery within the exclosures from pretreatment grazing practices may require decades, or even intervention (i.e., stream restoration), before a substantial reduction in streambank erosion is noted.

Moisture Effects on Greenhouse Gases Generation in Nitrifying Gas-Phase Compost Biofilters

Gas-phase compost biofilters are extensively used in concentrated animal feeding operations to remove odors and, in some cases, ammonia from air sources. The expected biochemical pathway for these predominantly aerobic systems is nitrification. However, non-uniform media with low oxygen levels can shift biofilter microbial pathways to denitrification, a source of greenhouse gases. Several factors contribute to the formation of anoxic/anaerobic zones: media aging, media and particle structure, air velocity distribution, compaction, biofilm thickness, and moisture content (MC) distribution. The present work studies the effects of media moisture conditions on ammonia (NH(3)) removal and greenhouse gas generation (nitrous oxide, N(2)O and methane, CH(4)) for gas-phase compost biofilters subject to a 100-day controlled drying process. Continuous recordings were made for the three gases and water vapor (2.21-h sampling cycle, each cycle consisted of three gas species, and water vapor, for a total of 10,050 data points). Media moisture conditions were classified into three corresponding media drying rate (DR) stages: Constant DR (wetter media), falling DR, and stable-dry system. The first-half of the constant DR period (0-750 h; MC=65-52%, w.b.) facilitated high NH(3) removal rates, but higher N(2)O generation and no CH(4) generation. At the drier stages of the constant DR (750-950 h; MC=52-48%, w.b.) NH(3) removal remained high but N(2)O net generation decreased to near zero. In the falling DR stage (1200-1480 h; MC=44-13%) N(2)O generation decreased, CH(4) increased, and NH(3) was no longer removed. No ammonia removal or greenhouse gas generation was observed in the stable-dry system (1500-2500 h; MC=13%). These results indicate that media should remain toward the drier region of the constant DR (in close proximity to the falling DR stage; MC=50%, approx.), to maintain high levels of NH(3) removal, reduced levels of N(2)O generation, and nullify levels of CH(4) generation.

Biofilter Media Characterization Using Water Sorption Isotherms

Compost material has been used extensively as a gas-phase biofilter media for contaminant gas treatment in recent years. One of the biggest challenges in the use of this type of material is adequate control of compost moisture content and understanding its effect on the biofiltration process. The present work provides a methodology for characterization of biofilter media under low moisture conditions. Results indicated that low levels of equilibrium moisture content (EMC) were obtained for high levels of equilibrium relative humidity (ERH), i.e., 99% ERH produced EMC of approximately 20% (dry basis) at 25°C. Most bacteria struggle to survive in environments with ERH levels lower than 95%. Compost material from the same source was sieved into four compost particle size (PS) ranges to evaluate its water sorption behavior: 4.76 mm > PS1 > 3.36�mm > PS 2 > 2.38 mm > PS3 > 2.00 mm > PS4 > 1.68 mm. Observed data were tested against isotherm models for their goodness-of-fit. Seven isotherm models were compared: (1) Langmuir; (2) Freundlich; (3) Sips; (4) Brunauer, Emmett, and Teller (BET); (5) BET for n-layers; (6) Guggenheim, Anderson, de Boer (GAB); and (7) Henderson. In comparison with the other models, the Henderson model provided the best fit, as determined by the best combination of regression coefficient standard errors () and coefficients of determination (r 2 ) for all four particle size ranges tested (95% confidence interval, C.I., and prediction interval, P.I.). The Henderson model was then used to test for significant differences in isotherms by particle size ranges. The four tested particle size ranges were not significantly different from each other (p < 0.05), indicating similar water sorption behavior. Data from all four particle size ranges were pooled and regressed, and the minimum required moisture to maintain ERH at or above 95% was 16.41% ±2.68% (dry basis).

Influence of BMPs on Cattle Position Preference

The beef industry is an important component of Kentucky’s agriculture accounting for approximately 15% of the state’s agricultural sales in 2000. Dairy also plays a prominent role in Kentucky’s agriculture (state rank of 18th). The state’s significant cattle production occurs primarily on small to mid-sized farms averaging between 25 and 40 head of cattle per operation. Considering this upward trend in cattle production along with Kentucky’s 140,000 km of rivers and streams, rolling pastures and karst geology, the potential for damage to riparian ecosystems from uncontrolled livestock access is high. The objective of this project was to determine the influence of alternate management strategies such as off-stream water, fencing, shade (permanent and movable), and pasture improvements on cattle behavior in grazed pastures of the humid region of the U.S. The project site, located on the University of Kentucky’s Animal Research Center, consisted of two replications of three treatments: control, selected BMPs with free access to the stream, and selected BMPs with limited access to the stream. Cattle placed on the research pastures were fitted with GPS collars to track their positions. The use of GPS collars for tracking animal movements and behaviors eliminates errors often introduced in human observations. GPS collar data was collected at five minute intervals for seven sampling events over a two year period. Results indicated that the BMP systems (i.e. treatments) did not affect cattle position preference, and as such, these BMP systems did not decrease the amount of time cattle spent along the streambanks. However, significant time effects were noted the cooling pasture feature trees as cattle sought relief from the heat and humidity. Increased cattle presence along the streambank during the daytime period was linked to longer day light hours, but the impractical nature of the model indicated that additional independent variables were required. For the nighttime data set, the significant seasonal variable was solar radiation, as decreases in solar radiation resulted in the model predicting that cattle would tend to avoid the pasture feature trees. The majority of non-zero solar radiation values, while relatively small in comparison to the daytime values, were in the periods dividing daytime and nighttime (i.e. dawn and dusk). Thus, the primary driving factor with regards to cattle position preference appeared to be a desire to avoid trees, a pasture feature often associated with loafing, possibly in favor of grazing. While the results of this study indicated that no significant treatment effects were present, the significant time effects suggest that the strategic development of 1) cooling features such as shade, wading ponds or water misters and 2) areas of high forage quality and quantity may influence cattle position preference.

Contaminant gas Generation as Product of Degraded Ammonia during Biofiltration

Biofiltration technology is widely utilized for treatment of ammonia gas, with one of its potential detrimental by-products being nitrous oxide, a powerful greenhouse gas. The present work intends to provide the relation between ammonia elimination capacity during biofiltration and nitrous oxide generation as product of incomplete denitrification. Four laboratory scale tubular biofilters in up flow mode (3 replicates receiving humidified air and ammonia and 1 control receiving only humidified air) will be studied and compared for three levels of ammonia volumetric loadings (4.8, 7.2, and 9.6 g m-3 h-1). Trends from the obtained ammonia and nitrous oxide relation in the laboratory will be evaluated for significance of nitrous oxide production under varied ammonia loadings.

Characterizing Physical Properties of Gas-Phase Biofilter Media

Gas-phase biofiltration is an effective technology for reduction of odors and trace-gas contaminants. Significant contributions to the technical literature regarding the characterization of biofilter media have been generated in the past two decades. Nevertheless, the information produced has not been systematically organized. The objective of this study is to demonstrate and document methods for physical characterization of gas-phase compost biofilters (GPCB). The inclusion of moisture content, compaction, and particle size effects in the determination of media bulk density and porosity, field capacity, drying rate analysis, water sorption isotherms, and resistance to airflow is demonstrated. Results indicated that: (1) higher moisture content led to about 2% reduction in porosity after compaction; (2) biofilter media sieved into three particle size ranges (12.5 mm > PSR1 > 8.0 mm > PSR2 > 4.75 mm > PSR3 > 1.35 mm) produced significantly different media field capacities, i.e., 52.8% (PSR1), 61.6% (PSR2), and 72.2% (PSR3) on a wet basis; (3) a drying rate analysis provides important information regarding media-water relations and can be potentially used for in situ indirect media moisture monitoring (as shown in previous work, changes in drying rate significantly affected ammonia removal and nitrous oxide generation); (4) the Henderson isotherm can be accurately used for dry organic media to determine the minimum moisture required for microbial activity; and finally (5) the combination of high airflow and high moisture content drastically increased pressure drop up to 65-fold (6350 Pa m-1) compared to the lowest pressure drop (98 Pa m-1). Further, the research community should integrate efforts to elaborate standard methods and protocols for physical characterization of gas-phase biofilter media before and during biofilter operation.

Effects of cattle grazing and BMPs on stream water quality

Cattle production is a major component of Kentucky’s agricultural economy, accounting for approximately 15% of the total agricultural sales in 2000. There are over 2.2 million beef cattle and calves in the state making Kentucky the number one beef producer east of the Mississippi River. Research into the effects of cattle grazing on stream water quality has been well documented in the western portion of the United States with some estimates indicating that 80% of the damage to riparian areas was caused by grazing livestock. However, the impacts of grazing cattle in a humid environment may differ significantly from those witnessed in the arid West. Furthermore, relatively little information exists regarding the effectiveness of grazing best management practices (BMPs), such as alternate water sources, alternate shade sources, supplemental feeding, and riparian buffers, for improving the water quality of streams in grazed watersheds of the humid region. As part of a larger research endeavor into cattle production practices in the humid region, water samples were collected over a two year period at the project site located on the University of Kentucky’s Animal Research Center. The project sites consisted of two replications of three treatments: control, selected BMPs with free access to the stream, and selected BMPs with limited access to the stream. Grab samples were collected at the upstream and downstream pasture edges. Samples were analyzed for nitrate-nitrogen, ammonium-nitrogen, total Kjeldahl nitrogen, dissolved orthophosphate, total phosphorus, total suspended solids, pH, chemical oxygen demand, five-day biochemical oxygen demand, fecal coliforms, and fecal streptococci. Results indicated that minimal water quality benefits were incurred by implementing the BMP systems (i.e. treatments). One of the most substantial understandings gleaned from the project was the importance of upstream land use, and to some degree soils, when attempting to identify significant treatment effects within a small reach. Additionally, the karst geology, which is characteristic of the Bluegrass Region of Kentucky, influenced the rate of transport (i.e. flashy system with quick response time to rainfall) of nutrients from upland areas (i.e. row crops), especially along Pin Oak. These external factors may have resulted in the lack of uniformity in significant constituent concentration differences between the two streams when cattle were present. Furthermore, the background constituent concentration levels may have prohibited the identification of treatment effects. Results from this project indicated that minimal water quality benefits were incurred by implementing a BMP system (with or without a partially excluded riparian zone). However, these results may differ if cattle were completely excluded from the stream or if the BMP system was implemented at a site with larger pastures, different geology (nonkarst), soils (low in phosphorus), or stream morphology (nonbedrock bottom channel).

Retention of gasification-combustion products by corn.

ABSTRACT Shelled corn was dried in layers of 5.1 cm (2 in.) 10.2 cm (4 in.), and 15.2 cm (6 in.) using air heated with the exhaust from a corn-cob fueled gasification-combustion updraft furnace. The drying air entering and leaving the grain layers was sampled for particulate content to determine the percentage of total particulates trapped by the grain during drying. It was determined that an average of 25% of the total particulates in the drying air were retained by the grain. The large majority of those particulates retained were found in the bottom 5.1 cm (2 in.) of the grain layer.