Analysis of the Sediment Filtering Action of Grassed Media

The movement of sediment in non-submerged flow through a rigid grass media was studied experimentally by simulating the media with cylindrical nails. Models of sediment movement were developed from probablistic reasoning and from the use of existing parameters describing total bed material in open channel flow. In the probability analysis, the percent sediment trapped was found to be a power function of the number of potential fall paths, Nf,a particle could make from the surface to the bed while traveling through the filter media. The percent trapped was also found to be an inverse power function of the Reynolds number ReT. The characteristic length used in the Reynolds number was a hydraulic radius calculated assuming rectangular open channel flow with a width equal to the spacing between elements and a depth equal to the depth of flow. This is defined as the spacing hydraulic radius, Rs. The percent trapped was finally related exponentially to a combined power function of Nf and ReT. Total bed material transport functions of Graf and Einstein were modified and evaluated as predictors of suspended and bed load. Bed shear was assumed to be equal to γRsS where γ is the weight density of water and S is channel slope. Both Graf\u27s and Einstein\u27s parameters were found to be good predictors of suspended and bed load. Based on the results of the study, procedures are proposed for analyzing the trapping capability of sediment by grass filters

Determination of Soil Contaminant Transport Parameters Using Time Domain Reflectometry

Proceedings of the 1993 Georgia Water Resources Conference, April 20-21, 1993, Athens, Georgia.A recent study of rural shallow drinking wells found that 4.6% of the wells in the Piedmont region of Georgia had nitrate levels above the EPA recommended level of 10 ppm nitrate nitrogen (Tyson and Issac, 1991). The most likely sources of this nitrate are septic systems, fertilizers, and manures. Nitrate transport models such as LEACHN (Wagenet and Hutson, 1989) can be used to investigate the contributions of these sources to groundwater contamination, but the models require soil transport parameters that are difficult to measure. Another problem is that we are interested in predicting nitrate transport at the field scale, but transport parameters are usually measured on a much smaller soil volume.Sponsored and Organized by: U.S. Geological Survey, Georgia Department of Natural Resources, The University of Georgia, Georgia State University, Georgia Institute of TechnologyThis book was published by the Institute of Natural Resources, The University of Georgia, Athens, Georgia 30602 with partial funding provided by the U.S. Department of Interior, Geological Survey, through the Georgia Water Research Institute as authorized by the Water Resources Research Act of 1984 (P.L. 98-242). The views and statements advanced in this publication are solely those of the authors and do not represent official views or policies of the University of Georgia or the U.S. Geological Survey or the conference sponsors

Tools for Remotely Assessing the Impact of Riparian Buffers Protecting Streams from Sediment Pollution

Proceedings of the 2007 Georgia Water Resources Conference, March 27-29, 2007, Athens, Georgia.A software package was assembled and evaluated for assessing the potential of soil erosion due to agricultural development within the Nzoia River basin (Kenya). Google Earth Pro was used to define site characteristics. An extensive analysis of the components of the Universal Soil Loss Equation (USLE) and the US Forest Service sediment delivery ratio method was made to determine erosion potential and sediment yield respectively. The paired t-test comparison between GPS elevation and Google earth derived elevation showed difference between the elevations but the error margin was within the GPS unit’s error margin of 5 meters. The ground truth results obtained from measured data for Watkinsville (US) and Bukora (Uganda) watersheds compared to the predicted values yielded 6 % average deviation and 10.5 % average deviation respectively with R2 of 0.995. The Moore and Sergoit bridge sites located near Eldoret, Kenya were analyzed. The predicted average soil loss at Moore’s bridge site was 192 tons ha-1 yr-1 with a stream sediment yield of 1.8 tons ha-1 yr-1 while at Sergoit site is 5.3 tons ha-1 yr-1with a stream sediment yield of 0.05 tons ha-1 yr-1. It was deduced that Google Earth Pro is useful for the initial surveys in extracting site topographic and land use patterns. The Preliminary results suggested that agricultural pollution is not a threat in this particular region but would become as more riparian zones are cleared. Also, the rainfall energy of the region is close to that in the US, common crops of the US are in production, and the soils of the region are of the Ultisol and Oxisol classification (southeast US). Therefore, the US experience would be applicable.Sponsored and Organized by: U.S. Geological Survey, Georgia Department of Natural Resources, Natural Resources Conservation Service, The University of Georgia, Georgia State University, Georgia Institute of TechnologyThis book was published by the Institute of Ecology, The University of Georgia, Athens, Georgia 30602-2202. The views and statements advanced in this publication are solely those of the authors and do not represent official views or policies of The University of Georgia, the U.S. Geological Survey, the Georgia Water Research Institute as authorized by the Water Resources Research Act of 1990 (P.L. 101-397) or the other conference sponsors

Measuring the efficacy of a root biobarrier with x-ray computed tomography

X-ray computed tomography is a useful tool for investigating soil physical properties nondestructively. There is a need to develop proper calibration relationships between soil properties and the x-ray absorption coefficient. The objective of the work was to evaluate soil factors affecting the x-ray absorption coefficient. Based on a theoretical analysis, experimental data from five soils and on results of several other investigators, it was concluded that for many applications, one calibration relationship is applicable to a wide range of soils. The montmorillinitic clay used in the study required special handling due to the extreme shrinkage of this soil upon drying. Knowledge of chemical composition enables approximations but not exact predictions of the x-ray absorption coefficient. The results suggested some reasonable alternative to exhaustive calibration for each anticipated soil condition. Quantification of root activity in terms of root growth and indirectly through water uptake is necessary for understanding plant growth dynamics. X-ray computed tomography (CT) enables qualitative as well as two quantitative outputs, one of which can lead to conclusions regarding root activity. A greenhouse study involving soil columns (Lakeland sand, bulk density 1.4 Mg/m{sup 3}) planted to soybean, Bahiagras, and control (no vegetation) was conducted in 1989. A treflan based on chemical barrier was placed in half of the soil column of each species. The mean x-ray absorption correlated to water content. Results suggested that root presence can also be indirectly inferred based on water content drawn down during planned stress events. It was concluded that x-ray CT may have a niche in soil-water-plant relation studies, particularly when plant species have large roots. 35 refs., 13 figs., 8 tabs

Bioconversion of Wool Industry Solid Wastes to Value-Added Products

[Yang, C.Q. and Zhang, L. listed on program, but not found on document]Two wool industry solid wastes presently landfilled were characterized for their potential for bioconversion to a value added product. The fibrous wastes were tested for physical and chemical properties and baseline biological degradation tests were performed. Carbon amendments were mixed with the wool waste and increased bio-stabilization was evaluated. The product of bioconverison was tested for chemical and agronomic properties, stability and phytotoxicity and weed seed destruction. Cotton gin trash was found to be the best among tested amendments, and it was seen that amending the wool wastes and composting increased its stability and reduced phytotoxicity. Weed seeds were present in fresh cotton gin trash, however, no germination of weed seeds were seen in any of the composted materials. It is felt that the final product can serve as a good slow N-release, highly water retaining soil amendment. Further work needs to be performed to enhance the physical nature of the product making it more suitable for storage, transportation and application

Integrating Design Criteria for Management of Urban Ecosystems

Proceedings of the 2003 Georgia Water Resources Conference, held April 23-24, 2003, at the University of Georgia.Urban streams are the confluence of human activity and natural system processes, oftentimes revealing the conflicting objectives of both. Ramifications of poor stream condition have not gone unnoticed as nationwide stream restoration efforts focus on restoring natural conditions based on criteria for ecological health and integrity. Urban watersheds suffer from poor water quality, degraded physical habitat and excessive stormwater runoff as a result of stream channelization, stream bank armoring and a high percentage of impervious landscape within the catchment. The objectives of this paper are to present current efforts in developing a framework for urban watershed management by integrating the concepts and principles of three design paradigms: 1) environmental design, 2) ecological design and 3) engineering design. The focus is to integrate the stream with its urban landscape through long-term management

Modeling Product Flow Through a Generic Post-Harvest Distribution System

A spreadsheet-based stochastic model was developed to track fruit numbers and fruit value for 1,000 individual items grown in a farmer's field, sorted at a packinghouse with and without advanced inspection technology, distributed with and without repack, and sold at a retail store. The quantities generated at each step are value per unit volume in the production field and the respective price multipliers and passing fractions at the packinghouse, distribution center, and retail store. Values of these coefficients were set to reflect experience with the onion industry. It was assumed that about 30% (with repackaging) to 40% (without repackaging) of the fruit leaving the farmer's field would reach the consumer. The initial price per unit volume and pricing multipliers were configured to give representative prices at the production field and representative price per unit fruit at steps through the system to the consumer. The pass-through percentage was decreased an extra 10% to 15% with technology and up to 20% with repack, with corresponding increases in subsequent steps to maintain the 25% to 25% total pass-through. Repacking and technology addition in the packinghouse tended to result in increased value at the retail level. Placing technology in the packinghouse did not result in increased value for the packinghouse. Vertical integration that included the packinghouse would be required to make it profitable to add sorting technology that increases quality by removing defective items. Both technology addition and repackaging reduce the total number of fruits reaching the consumer. The model suggests that the notion of early removal of fruits with latent damage to avoid increased distribution costs does not really benefit the consumer for the conditions modeled. Additional considerations such as food security are required for one to expect additional equipment adoption under current scenarios

Streamflow Separation to Estimate Daily Unregulated Streamflow of Ungauged Watersheds in the Coastal Plains of Southeastern United States

2012 S.C. Water Resources Conference - Exploring Opportunities for Collaborative Water Research, Policy and Managemen