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Riverine nitrate N in the Mississippi River leads to hypoxia in the Gulf of Mexico. Several recent modeling studies estimated major N inputs and suggested source areas that could be targeted for conservation programs. We conducted a similar analysis with more recent and extensive data that demonstrates the importance of hydrology in controlling the percentage of net N inputs (NNI) exported by rivers. The average fraction of annual riverine nitrate N export/NNI ranged from 0.05 for the lower Mississippi subbasin to 0.3 for the upper Mississippi River basin and as high as 1.4 (4.2 in a wet year) for the Embarras River watershed, a mostly tile-drained basin. Intensive corn (Zea mays L.) and soybean [Glycine max (L.)...
Nitrate leaching in the unsaturated zone poses a risk to groundwater, whereas nitrate in tile drainage is conveyed directly to streams. We developed metamodels (MMs) consisting of artificial neural networks to simplify and upscale mechanistic fate and transport models for prediction of nitrate losses by drains and leaching in the Corn Belt, USA. The two final MMs predicted nitrate concentration and flux, respectively, in the shallow subsurface. Because each MM considered both tile drainage and leaching, they represent an integrated approach to vulnerability assessment. The MMs used readily available data comprising farm fertilizer nitrogen (N), weather data, and soil properties as inputs; therefore, they were well...
The biogeochemical impacts of alternative management practices for a row-crop field in Iowa were modeled. Numerous field measurements were made to quantify the impacts of no-till on crop yields, soil organic carbon (SOC) dynamics, nitrate leaching, and trace gas emissions. The observations provided first-hand information to understand the comprehensive effect of an alternative tillage method on agricultural production and the environment. Field observations indicated that the impacts of no-till on the Midwestern agro-ecosystems were highly variable in space and time due to the companion management practices, as well as the climatic and soil conditions. The modeled results indicated that the best management practices...
The influence of the proximity of urbanization and agriculture to stream water quality is often difficult to quantify. The objectives of this study were to (1) compare the influence of far-field land-use, encompassing a watershed drainage area, to a near-field, 200-m buffer on each side of the stream in an attempt to determine on which zone of influence land-use has the largest impact on water quality, and (2) incorporate the EPA's Rapid Habitat Assessment Protocol (Barbour et al., 1999) to characterize the riparian and channel characteristics of a stream that influence water quality, which can improve New York State's monitoring protocols. Impacts were assessed through biological, chemical, and physical-habitat...
Systems thinking and system dynamics simulation can provide insights for developing effective plans to protect the environmental integrity of natural systems impacted by human activities. In this study, a system archetype known as growth and underinvestment is hypothesized to explain the eutrophication problem of Lake Allegan in Michigan and identify policy leverage points for mitigation. An integrated system dynamics model is developed to simulate the interaction between key socioeconomic subsystems and natural processes driving eutrophication. The model is applied to holistically characterize the lake’s recovery from its hypereutrophic state and assess a number of proposed total maximum daily load (TMDL) reduction...
Quantifying and evaluating effects of best management practices (BMPs) on water quality is necessary to maximize the effectiveness of BMPs for minimizing pollutants. Watershed-scale evaluation of effects of BMP implementation on fecal bacteria and sediment yield can be estimated using a watershed water quality model, and strategies for identifying critical areas in a watershed can be pollutant specific. The soil and water assessment tool (SWAT) model was used in the Upper Wakarusa watershed (950 km2) in northeast Kansas to explore effectiveness of vegetative filter strip (VFS) lengths applied at the edge of fields to reduce non-point source pollution. The Upper Wakarusa watershed is a high priority total maximum...
This research examines the effects of climate change on the species composition of forests in the southern Great Lakes region in USA (Illinois, Indiana, and Ohio) by simultaneously addressing five key components necessary for realistic predictions of future forest composition. We simulated transient (1), species-level (2), forest response to climate change at a spatial scale that accounted for competitive effects (3), and regional site diversity (4), in the spatial configuration of forests within the regional landuse matrix (5). The JABOWA-II forest growth model was used to provide species-specific responses of 45 tree species to site conditions (e.g. climatic, edaphic) while accounting for competition for limited...
Water erosion results in the mobilization and depletion of soil organic carbon (SOC), but studies providing direct experimental evidence of eroded C mineralization and its linkage to the global C cycle are lacking. A study was conducted to determine the mineralization of SOC in runoff from a southwestern Ohio Crosby soil (fine, mixed, mesic Aeric Ochraqualf) that had been under no-till (NT), chisel till (CT) and moldboard plow (MP) for 38 years. To simulate present and future soil erosion conditions, the 0–3 and 5–8 cm soil layers from triplicate soil blocks extracted from each tillage practice were used. Soil layers were transferred to runoff trays and simulated rainfall (30±5 mm h−1) was applied for 1 h. Runoff...
Carbon sequestration has been well recognized as a viable option to slow the rise in atmospheric greenhouse gas concentration. The main goals of this study were to assess the carbon sequestration potential (CSP) by afforestation of marginal agricultural land (MagLand) and to identify hotspots for potential afforestation activities in the U.S. Midwest region (Michigan (MI), Indiana (IN), Ohio, Kentucky (KY), West Virginia, Pennsylvania (PA) and Maryland (MD)). The 1992 USGS National Land Cover Dataset and the State Soil Geographic (STATSGO) database were used to determine MagLand. Two forest types (coniferous and deciduous) and two management practices (short-rotation versus permanent forest) were combined to form...
An accurate and management sensitive simulation model for tile-drained Midwestern soils is needed to optimize the use of agricultural management practices (e.g., winter cover crops) to reduce nitrate leaching without adversely affecting corn yield. Our objectives were to enhance the Agricultural Production Systems Simulator (APSIM) for tile drainage, test the modified model for several management scenarios, and then predict nitrate leaching with and without winter wheat cover crop. Twelve years of data (1990–2001) from northeast Iowa were used for model testing. Management scenarios included continuous corn and corn–soybean rotations with single or split N applications. For 38 of 44 observations, yearly drain flow...
The potential for global climate changes to increase the risk of soil erosion is clear, but the actual damage is not. The objectives of this study were to evaluate the potential impacts of climate change on soil erosion, surface runoff, and wheat productivity in central Oklahoma. Monthly projections were used from the Hadley Centre's general circulation model, HadCM3, using scenarios A2a, B2a, and GGa1 for the periods of 1950-1999 and 2070-2099. Projected changes in monthly precipitation and temperature distributions between the two periods were incorporated into daily weather series by means of a stochastic weather generator (CLIGEN) with its input parameters adjusted to each scenario. The Water Erosion Prediction...
Soil erosion under future climate change is very likely to increase because of increases in occurrence of heavy storms. The objective of this study is to quantify the effects of common cropping and tillage systems on soil erosion and surface runoff during 2010 to 2039 in central Oklahoma. A combination of 18 cropping and tillage systems is evaluated using the Water Erosion Prediction Project (WEPP) model for 12 climate change scenarios projected by four global climate models (GCMs) under three emissions scenarios. Tillage systems include conventional, reduced, delayedno tillage. Cropping systems include continuous monocultures of winter wheat, soybean, sorghumcotton and double crops of wheat and soybeans. Compared...
DWSM, the dynamic watershed simulation model, was expanded with a subsurface and a reservoir flow routing schemes. The hydrology and sediment components of the model were applied to three agricultural watersheds in Illinois, Big Ditch (100 km2), Court Creek (250 km2), and Upper Sangamon River (2,400 km2), to simulate spatially and temporally varying surface and subsurface storm water runoff, propagation of flood waves, upland soil and streambed erosion, and sediment transport; to evaluate these simulation capabilities through calibration and validation; and to conduct various watershed investigative analyses. The new schemes were selected from the literature. DWSM was able to simulate the major hydrologic, soil...
The Pocono Creek watershed drains 46.5 square miles in eastern Monroe County, Pa. Between 2000 and 2020, the population of Monroe County is expected to increase by 70 percent, which will result in substantial changes in land-use patterns. An evaluation of the effect of reduced recharge from land-use changes and additional ground-water withdrawals on stream base flow was done by the U.S. Geological Survey (USGS) in cooperation with the U.S. Environmental Protection Agency (USEPA) and the Delaware River Basin Commission as part of the USEPA’s Framework for Sustainable Watershed Management Initiative. Two models were used. A Soil and Water Assessment Tool (SWAT) model developed by the USEPA provided areal recharge...
The purpose of this paper is to expand debate about the future landscapes of the upper Midwest of the United States. The paper addresses options that could reinvent the agricultural systems of the Corn Belt, which coincides with the Upper Mississippi River Basin. The changes would move this region from one dependent on a grain economy, with low economic returns and high nutrient and sediment losses, to a more ecologically-based landscape emphasizing nutrient sinks, especially for nitrogen, and a legume base for supplementing fertilizer nitrogen. The reinvented systems require a higher level of management to lessen nitrogen and phosphorus losses while supporting family farms and strong rural communities. This reinvented...
Improved understanding of year-to-year late-spring soil nitrate test (LSNT) variability could help make it more attractive to producers. We test the ability of the Root Zone Water Quality Model (RZWQM) to simulate watershed-scale variability due to the LSNT, and we use the optimized model to simulate long-term field N dynamics under related conditions. Autoregressive techniques and the automatic parameter calibration program PEST were used to show that RZWQM simulates significantly lower nitrate concentration in discharge from LSNT treatments compared with areas receiving fall N fertilizer applications within the tile-drained Walnut Creek, Iowa, watershed (>5 mg N L-1 difference for the third year of the treatment,...
Summer air and stream water temperatures are expected to rise in the state of Wisconsin, U.S.A., over the next 50 years. To assess potential climate warming effects on stream fishes, predictive models were developed for 50 common fish species using classification-tree analysis of 69 environmental variables in a geographic information system. Model accuracy was 56·0-93·5% in validation tests. Models were applied to all 86 898 km of stream in the state under four different climate scenarios: current conditions, limited climate warming (summer air temperatures increase 1° C and water 0·8° C), moderate warming (air 3° C and water 2·4° C) and major warming (air 5° C and water 4° C). With climate warming, 23 fishes were...