Progress 10/01/12 to 09/30/13
Target Audience: The results of the infiltration index study are of interest to different groups, including soil scientists with USDA-NRCS, state regulators in charge of land application of wastes (e.g., onsite wastewater disposal) as well as storm water management, and professional consultants. The results of the study will be presented at various national and state scientific meetings as well as workshops through the NC Cooperative Extension programs. Changes/Problems:
What opportunities for training and professional development has the project provided?
How have the results been disseminated to communities of interest?
What do you plan to do during the next reporting period to accomplish the goals? A series of laboratory experiments will be conducted to assess the impact of temperature on soil saturated hydraulic conductivity.
What was accomplished under these goals?
A number of pedotransfer functions for estimating soil hydraulic properties were tested using a data set containing more than 700 data points. Using HYDRUS model, vertical water flow was simulated for 130 two-layer soils composed of a 10-cm thick top soil and 40-cm thick subsoil for determining infiltration and runoff. The data set was used to obtain saturated hydraulic conductivity, porosity and bulk density values of each layer for each simulation. In these simulations, the rainfall intensity was 54.8 mm/h (2 in/h), which represents a 5-year storm for North Carolina. For simulating water flow, the theoretical column was first saturated and then allowed to drain by gravity for 15 days. The simulated rainfall was then applied to the soil column and at the end of the simulation, the amounts of infiltration and runoff were determined. Taking the fraction of the rainfall amount that infiltrated the soil (i.e., cumulative infiltration divided by rainfall amount) as infiltration index, the results for various surface and subsurface pairs were divided into the best case, average and the worst case infiltration scenarios. Using available information for soil hydraulic properties for a given county, the infiltration index values obtained through HYDRUS model can be used in an appropriate geographic information system (GIS) mapping model to generate infiltration index maps for that county. In addition to the theoretical study, an experimental study was also initiated to assess infiltration and runoff using actual field soils. A 25.4-cm inside diameter and 50-cm long column was constructed from polyvinyl chloride (PVC) pipe. A 27.5-cm diameter porous plate was tightly attached to the bottom of the column for simulating water table at different depths. The column was packed in two layers with bulk soil materials collected from two different layers of a sandy soil. The column was saturated from the bottom, then drained by gravity before applying 5 cm of water while applying approximately100 cm of tension to the porous plate at the bottom of the column. By varying the amount of vacuum applied to the porous plate, infiltration into soil with different water table depths can be simulated. The column will be used to complement and validate the findings of the HYDRUS model simulations.
Conference Papers and Presentations
Lindbo, D.L., A. Amoozegar, D. Anderson, M.J. Vepraskas, and R. Vick. 2013. Hydropedology of a benchmark catena in the Carolina Slate Belt. ASA-CSSA-SSSA Annual Meetings, November 3-6, 2013, Tampa, FL.
Progress 10/01/11 to 09/30/12
OUTPUTS: Saturated hydraulic conductivity (Ksat) within a field in Orange County, NC, was measured in situ by the constant-head well permeameter technique at 9 locations using three replications. The cylindrical auger holes that were used for measurements were 6 cm in diameter and between 72 and 79 cm deep. The constant height of water in individual holes during measurements was maintained at 18.5 to 21.5 cm. In addition, percolation rates for the soil were measured in duplicates at three locations using 10 cm (4 in) holes that were approximately 70 cm deep. The depth of water in each hole during pre-saturation period and at the time of measurements was approximately 20 cm (8 in). Intact core samples, approximately 6.5 cm in diameter, were collected from different depths and locations with an agricultural field in Rowan County, NC. The core samples were cut to 10 cm length and analyzed for Ksat in the laboratory by the constant head method. For the samples with very low hydraulic conductivity, Ksat was remeasured by the falling head method. After Ksat measurements, some of the samples were analyzed for water retention. To develop an infiltration index for soils, a data base containing Ksat, texture and bulk density for more than 110 soils has been developed. In addition, a preliminary function has been generated using HYDRUS model to assess infiltration index for varying topsoil depth and hydraulic conductivity. PARTICIPANTS: David Lindbo was a PI on the projects to assess soil hydraulic conductivity as related to soils at the Orange Country site. Josh Heitman and David Lindbo are Co-PIs in the project to develop an infiltration index for the soils of the Piedmont region of North Carolina. Josh Heitman is also a Co-PI in another project, with Ronald Gehl as the PI, to assess the impact of various crops on soil physical properties in Rowan County. Amanda Liesch is a Ph.D. degree graduate student working on the project to develop the infiltration index mentioned above. Philip Schoeneberger, National Soil Survey Center, USDA-NRCS, Lincoln, Nebraska, is a collaborator on the infiltration index project TARGET AUDIENCES: The groups interested in the finding of the study include soil scientists with USDA-NRCS, state regulators in charge of land application of wastes, particularly on-site wastewater and storm water management systems, and professional consultants. Finding of the study will be presented to these and other interested individuals through journal publications and presentations at National and state meetings. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
The preliminary results indicate a high degree of variability among both Ksat and percolation rate values at the Orange Country site. Although the individual percolation rates calculated using the flow rate values measured in 6-cm diameter holes during in situ Ksat measurements at the site were numerically different than the measured percolation rates, there was a general agreement between the two techniques for the three locations. This indicates a potential for converting a measured Ksat value to percolation rate for site assessment and determining loading rates for designing on-site wastewater disposal (also referred to as wastewater dispersal) systems, but additional research must be conducted for developing an appropriate conversion factor that may depend on soil type. The preliminary assessment of Ksat values determined for the site in Rowan County indicates a high degree of variability among Ksat values for different depths. More modeling is being conducted for developing an infiltration index using larger data bases.
- Abit, S. M., A. Amoozegar, M. J. Vepraskas, C. P. Niewoehner. 2012. Soil and hydrologic effects on fate and horizontal transport in the capillary fringe of surface-applied nitrate. Geoderma 189-190: 343-350.
- Abit, S. M., M. J. Vepraskas, O. W. Duckworth, and A. Amoozegar. 2012. Dissolution of Phosphorus into Pore-Water Flowing through an Organic Soil. Geoderma (Accepted for publication).
- Stall, C. A. Amoozegar, D. Lindbo, A. Graves, and D. Rashash. 2012. Transport of E. coli in a sandy soil as impacted by depth of water table. J. of Environ. Health. (Accepted for publication).
- Amoozegar, A. 2012. Data Requirements for Calibrating Hydrologic Models. Abstract. Soil Sci. Soc. Am. Ann. Meeting, Cincinnati, OH.
Progress 10/01/09 to 09/30/10
OUTPUTS: Five equidistant locations were selected on a transect going through a Georgeville soil toposequence in a pasture and its adjoining wooded area in Orange County, NC. Location 1 was on the shoulder landscape position with 5% slope. Locations 2 and 3 were on a side slope with a slope of 9 and 17%, respectively. Location 4 was on the toe slope position with a slope of 1%, and location 5 was in a stream bed at the base of the landscape. An observation/sampling pit was dug at each of the five locations. The soil profile was described according to USDA-NRCS field guide, and a minimum of three 7.6 cm in diameter and 7.6 cm long intact core samples were collected from each of the 4, 76, and 107 cm depths at each location. In addition, saturated hydraulic conductivity (Ksat) at each depth was measured in situ by the constant-head well permeameter technique at three places within a small area at each location. In situ measurement was conducted by maintaining a minimum of 15-cm depth of water (H) at the bottom of a 6-cm diameter (2r) cylindrical hole, and measuring the steady-state rate of water flow (Q) into the hole. Saturated hydraulic conductivity was calculated by the Glover model using Q, H and r. In the laboratory, the intact samples were saturated from the bottom and analyzed for Ksat by the constant head procedure. For this measurement, a cylinder was attached and sealed to the top of the cylinder containing the soil and a constant depth of water was maintained on top of the saturated core until the outflow from the core reached steady-state. Saturated hydraulic conductivity was calculated using Darcy's Law. If the flow rate from any core was less than 1 cubic cm per minute, falling head procedure was employed for measuring Ksat. Using the soil texture and other morphological properties of the soil determined in the field, a long-term acceptance rate (LTAR) for an on-site wastewater dispersal system (i.e., septic system) was assigned to each location based on the prevailing North Carolina regulations governing on-site wastewater management. The arithmetic and geometric mean Ksat values for each location was also converted to an equivalent loading rate and compared to LTAR determined from morphological data according to North Carolina regulations. PARTICIPANTS: The following individuals were involved in the conduct of the research reported here. David Lindbo was a PI on the projects to assess soil hydraulic conductivity as related to soils in the Georgeville Catena. Sloan Griffin was a MS degree graduate student who conducted the field and laboratory study and completed his degree requirements at the end of 2009. Josh Heitman was a member of Griffin's committee. Roy Vick, NC State Soil Scientist for USDA-NRCS, was a collaborator on the project. The preliminary results of the study were presented at the ASA, CSSA, and SSSA International Annual Meeting in Long Beach, CA. TARGET AUDIENCES: The groups interested in the finding of the study include soil scientists with USDA-NRCS, state regulators in charge of land application of wastes, particularly on-site wastewater management systems, and professional consultants. Finding of the study will be presented to these and other interested individuals through a series of seminars and workshops. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Based on the morphological properties of the soil assessed on site, the soils at locations 1 and 2 were mapped as Georgeville. The soils at locations 3 and 4 were mapped as Tatum and the soil at location 5 was mapped as Chewacla series. The laboratory measured Ksat values had a considerably higher variability than in situ measured values, but there was no significant difference between the laboratory measured and in situ measured Ksat values at any depth-location. The geometric mean values for both in situ and laboratory measured Ksat values were less than the permeability values reported in USDA-NRCS Soil Survey for Orange County, NC. The LTAR values determined using laboratory Ksat values were consistently higher than the LTAR values determined based on soil morphology. The LTAR values determined using in situ measured Ksat, however, were closer to their corresponding morphology-based LTAR values.
- Stanford, B. D., A. Amoozegar, and H. S. Weinberg. 2010. The impact of co-contaminants and septic system effluent quality on the transport of estrogens and nonylphenols through soil. Water Research 44:1598-1606
- Amoozegar, A., D. Lindbo, J. Heitman, M. Vepraskas, S. Abit, and C. Stall. 2010. Fate and transport of septic system effluent in the vadose zone. Abstract, ASA, CSSA, and SSSA International Annual Meetings. Oct. 31-Nov. 4, Long Beach, CA. Sloan, G., D. Lindbo, A. Amoozegar, and J. Heitman. 2010. Comparison of field and lab Ksat measurements and relation to onsite wastewater system design. Abstract, ASA, CSSA, and SSSA International Annual Meetings. Oct. 31-Nov. 4, Long Beach, CA. Vepraskas, M, J. Heitman, J. Shaw, and A. Amoozegar. 2010. Extrapolating climate-change predictions of hydrology across regions using soil and landscape data. Abstract, ASA, CSSA, and SSSA International Annual Meetings. Oct. 31-Nov. 4, Long Beach, CA.