COMPACT – A Reclamation Soil Compaction Model Part II. Sensitivity Analysis and Applications

COMPACT, a physically based, event-oriented compaction model, was developed as a management or research tool to evaluate the influence of a surface mining system on compaction of soil material during reclamation. Two systems of area mining reclamation operations were simulated by COMPACT. The first system involved scrapers and bulldozers and the second also included trucks. Scrapers or trucks were used to pick up and deposit the soil material. Bulldozers were then used to shape the site for reclamation. The simulated results were compared with measured results and show how equipment patterns and soil parameters can affect overall soil compaction. This simulation model allows equipment, soil material, and operational parameters to be changed easily so managers and researchers can understand the soil compaction processes at surface mine sites

COMPACT – A Reclamation Soil Compaction Model Part I. Model Development

A physically based, event oriented soil compaction model, known as COMPACT, was developed as a management or research tool to evaluate the effect of surface mining systems on compaction of soil material during reclamation. Simulation of compaction throughout the soil profile at a surface mining reclamation site requires information describing how equipment moves on the site. The compaction processes that are caused by vehicles throughout the soil profile are described by applying the pressure distribution of the surface contact area of a tire or track to determine stresses in the soil profile. A virgin compression curve is then used to determine bulk density at any point within the soil profile. COMPACT predicts compaction of reconstructed patterns, type of vehicles, and type of soil material. Development of the simulation model is described in this article

Simulation of Burley Tobacco Harvesting-Housing Systems

A computer model has been developed using systems analysis techniques to simulate the labor and equipment aspects of harvesting burley tobacco. By varying the parameters of the model the user can determine a harvesting and housing strategy based on labor and equipment availability

Evaluation of AnnAGNPS Model for Runoff Simulation on Watersheds from Glaciated Landscape of USA Midwest and Northeast

Runoff modeling of glaciated watersheds is required to predict runoff for water supply, aquatic ecosystem management and flood prediction, and to deal with questions concerning the impact of climate and land use change on the hydrological system and watershed export of contaminants of glaciated watersheds. A widely used pollutant loading model, Annualized Agricultural Non-Point Source Pollution (AnnAGNPS) was applied to simulate runoff from three watersheds in glaciated geomorphic settings. The objective of this study was to evaluate the suitability of the AnnAGNPS model in glaciated landscapes for the prediction of runoff volume. The study area included Sugar Creek watershed, Indiana; Fall Creek watershed, New York; and Pawcatuck River watershed, Rhode Island, USA. The AnnAGNPS model was developed, calibrated and validated for runoff estimation for these watersheds. The daily and monthly calibration and validation statistics (NSE \u3e 0.50 and RSR \u3c 0.70, and PBIAS ± 25%) of the developed model were satisfactory for runoff simulation for all the studied watersheds. Once AnnAGNPS successfully simulated runoff, a parameter sensitivity analysis was carried out for runoff simulation in all three watersheds. The output from our hydrological models applied to glaciated areas will provide the capacity to couple edge-of-field hydrologic modeling with the examination of riparian or riverine functions and behaviors

Assessing the Long Term Impact of Phosphorus Fertilization on Phosphorus Loadings Using AnnAGNPS

High phosphorus (P) loss from agricultural fields has been an environmental concern because of potential water quality problems in streams and lakes. To better understand the process of P loss and evaluate the effects of different phosphorus fertilization rates on phosphorus losses, the USDA Annualized AGricultural Non-Point Source (AnnAGNPS) pollutant loading model was applied to the Ohio Upper Auglaize watershed, located in the southern portion of the Maumee River Basin. In this study, the AnnAGNPS model was calibrated using USGS monitored data; and then the effects of different phosphorus fertilization rates on phosphorus loadings were assessed. It was found that P loadings increase as fertilization rate increases, and long term higher P application would lead to much higher P loadings to the watershed outlet. The P loadings to the watershed outlet have a dramatic change after some time with higher P application rate. This dramatic change of P loading to the watershed outlet indicates that a “critical point” may exist in the soil at which soil P loss to water changes dramatically. Simulations with different initial soil P contents showed that the higher the initial soil P content is, the less time it takes to reach the “critical point” where P loadings to the watershed outlet increases dramatically. More research needs to be done to understand the processes involved in the transfer of P between the various stable, active and labile states in the soil to ensure that the model simulations are accurate. This finding may be useful in setting up future P application and management guidelines

Modeling the contribution of ephemeral gully erosion under different soil managements: A case study in an olive orchard microcatchment using the AnnAGNPS model

A study was undertaken into the environmental and economic impacts of different soil management strategies, spontaneous grass cover with and without gully control (SC/SCGC) or conventional tillage with and without gully control (T/TGC), based on the experimental results obtained in an 6.1. ha olive crop microcatchment. Initially, 2. years of rainfall-runoff-sediment load data series, (34 events) recorded under the current management (SCGC), was used for the calibration of the AnnAGNPS model at event and monthly scales providing suitable adjustments of runoff, peak flow and sediment loads (. E>. 70, . r>. 0.85).Ephemeral gullies were also identified using aerial orthophotography and field work. The module of the AnnAGNPS model for simulating ephemeral gully generation and the tillage operations based on a bibliographical review were used to compare different scenarios and to perform a 10year-analysis. The results showed mean runoff coefficients of 10.0% for SC/SCGC and of 3.2% for T/TGC while the average sediment loads were 2.0t*ha -1*year -1 (SCGC), 3.5t*ha -1*year -1 (SC), 3.3t*ha -1*year -1 (TGC) and 4t*ha -1*year -1 (T). Significant differences in sediment sources (rill/inter-rill erosion and ephemeral gullies) were evaluated between SC (46% of gully contribution) and T (19% of gully contribution), in order to optimize the environmental and economic effort required in each case. Finally, the annual costs associated with soil losses were estimated (<1€*ha -1*year -1). SC was the most profitable alternative for soil management. Despite the additional reduction in soil losses of the SCGC approach, the higher cost of its implementation and the minor effect on yield losses in the medium term suggest that without additional support (such as subsidies for gully control measures), farmers would have not an obvious incentive to use it. © 2012 Elsevier B.V.Part of this study was supported by Projects P08-AGR-03925 (Andalusian Government) and AGL2009-12936-C03-01 (Spanish Ministry of Science and Innovation), RESEL (Spanish Ministry for Science and Environment) and by FEDER funds.Peer Reviewe

Evaluation of Alternative Management Practices with the AnnAGNPS Model in the Carapelle Watershed

The Annualized Agricultural Non-point Source (AnnAGNPS) model can be used to analyze the effects of management practices on sediment loads in agricultural watersheds. The study was performed in a 506 km2 Mediterranean watershed located in Apulia, Southern Italy, planted with mostly winter wheat (83%) where runoff and sediment loads have been monitored at an in-stream gage. The AnnAGNPS model was used to predict runoff and sediment load without calibration during a 5-year period. On an annual scale, the model showed good prediction capability for runoff (R2 = 0.8, NSE [Nash and Sutcliffe coefficient of efficiency] = 0.7) and satisfactory results for sediment load (NSE = 0.5, R2 = 0.5). Based on the current conditions of the watershed as a baseline scenario, the effectiveness of alternative conservation practices applied within the watershed was also evaluated. No-tillage practices applied to the entire cropland area reduced soil erosion within fields by 44% and sediment yield from fields to streams by 20%. Reduced tillage decreased soil erosion, sediment yield, and sediment load at the gage location by 12%, 7%, and 4% respectively. Limiting the placement of alternative practices to the cropland sub-watersheds with the most erosion (Scenarios G and H) proved to be a promising and viable approach to sediment erosion reduction throughout the watershed. In this perspective, areas that produce the most sediment were identified and targeted for replacement of varying levels of cropland with forest, and consequently sediment loads were reduced from 5% to 97%. The effect of vegetated streams and riparian buffers as natural traps that can increase the in situ sediment deposition was also considered. Most, but not all of the scenarios discussed herein could realistically be implemented within the watershed, particularly if there are incentive policies. Even considering the intrinsic uncertainty of modeling results, evaluating these systems with the aid of AnnAGNPS serves as a means to provide reference information and allows watershed conservation planners to compare the impacts of different management scenarios with sustainable agriculture guidelines

Evaluation of thiobencarb runoff from rice farming practices in a California watershed using an integrated RiceWQ-AnnAGNPS system

The development of modeling technology to adequately simulate water and pesticide movement within the rice paddy environment faces several challenges. These include: (1) adequately representing ponded conditions; (2) the collection/implementation of temporal/spatial pesticide application data at field scales; (3) the integration of various mixed-landuses simulation schemes. Currently available models do not fully consider these challenges and results may not be sufficiently accurate to represent fate and transport of rice pesticides at watershed scales. Therefore, in this study, an integrated simulation system, "RiceWQ-AnnAGNPS", was developed to fully address these challenges and is illustrated in a California watershed with rice farming practices. The integrated system successfully extends field level simulations to watershed scales while considering the impact of mixed landuses on downstream loadings. Moreover, the system maintains the application information at fine spatial scales and handles varying treated paddy areas via the "split and adjust" approach. The new system was evaluated by investigating the fate and transport of thiobencarb residues in the Colusa Basin, California as a case study. Thiobencarb concentrations in both water and sediment phases were accurately captured by the calibrated RiceWQ model at the edge of field. After spatial upscaling, the integrated system successfully reflected both the seasonal pattern of surface runoff and the timing of monthly thiobencarb loadings. Incorporating future enhancements can further improve model performance by including more detailed water drainage schedules and management practices, improving the accuracy of summer runoff estimations, and incorporating a more sophisticated in-stream process module. This integrated system provides a framework for evaluating rice pesticide impacts as part of a basin level management approach to improve water quality, which can be extended to other rice agrochemicals, or other areas with fine-scale spatial information of pesticide applications