Metamodels and Nonpoint Pollution Policy in Agriculture

Informed debate on agricultural nonpoint pollution requires evaluation of regional water quality in relation to management practices. It is prohibitive, in terms of cost and time, to run the site-specific process models for regional policy analysis. Therefore, a simplified and robust technique--metamodeling--is suggested to evaluate regional water quality. Data from an experimentally designed simulation of complex surface water and groundwater process models, PRZM and STREAM, are used to develop statistically validated metamodels. The estimated metamodels were integrated with a regional agricultural economic decision making model to evaluate the surface water and groundwater loadings of 16 major corn and sorghum herbicides. Spatial probability distributions are derived for herbicide concentrations exceeding the toxicity-weighted benchmark from the EPA. We estimate that 1.2 percent of the regional soils will lead to groundwater detection of atrazine exceeding 0.12 ?/L, which compares well with the findings of the EPA\u27s groundwater monitoring survey. We find no-till practices to significantly reduce the surface water concentration of atrazine and other herbicides with less impact on groundwater contamination suggesting indirect gains to soil conservation policies. But we also note that an atrazine ban could lead to increased soil erosion, even with the conservation compliance provisions fully incorporated

Corn and Sorghum Herbicides and Water Quality: An Evaluation of Alternative Policy Options

The policies restricting the use of atrazine and other triazines to achieve desirable water quality standards are analyzed in a CEEPES framework. Five policies, including atrazine post restriction, restricting atrazine to meet MCL and HAL standards in runoff, a complete ban on atrazine, and also a ban on all triazines, were evaluated. The results suggest a $764 million total economic welfare loss with a triazine ban; with all other policies there was only one-third as much economic welfare loss. Although the triazine ban produced desirable water quality benefits, the economic costs are significantly higher. The overall goal of reducing water quality risk with the least economic welfare loss would not be achieved through an atrazine ban either, unless producers adopt practices that minimize risk from substitute herbicides. The runoff standards-based policy restrictions and atrazine post restriction offer best results for minimizing environmental risks with the least welfare reduction, but the current analysis assumes zero transaction costs, namely zero cost of monitoring and assessment

Assessment of three long-term gridded climate products for hydro-climatic simulations in tropical river basins

10.3390/w9030229Water (Switzerland)9322

Interplay between spatially explicit sediment sourcing, hierarchical river-network structure, and in-channel bed material sediment transport and storage dynamics

Understanding how sediment moves along source to sink pathways through watersheds„from hillslopes to channels and in and out of floodplains„is a fundamental problem in geomorphology. We contribute to advancing this understanding by modeling the transport and in-channel storage dynamics of bed material sediment on a river network over a 600æyear time period. Specifically, we present spatiotemporal changes in bed sediment thickness along an entire river network to elucidate how river networks organize and process sediment supply. We apply our model to sand transport in the agricultural Greater Blue Earth River Basin in Minnesota. By casting the arrival of sediment to links of the network as a Poisson process, we derive analytically (under supply-limited conditions) the time-averaged probability distribution function of bed sediment thickness for each link of the river network for any spatial distribution of inputs. Under transport-limited conditions, the analytical assumptions of the Poisson arrival process are violated (due to in-channel storage dynamics) where we find large fluctuations and periodicity in the time series of bed sediment thickness. The time series of bed sediment thickness is the result of dynamics on a network in propagating, altering, and amalgamating sediment inputs in sometimes unexpected ways. One key insight gleaned from the model is that there can be a small fraction of reaches with relatively low-transport capacity within a nonequilibrium river network acting as ñbottlenecksî that control sediment to downstream reaches, whereby fluctuations in bed elevation can dissociate from signals in sediment supply. ©2017. American Geophysical Union. All Rights Reserved

Atrazine and Water Quality: An Evaluation of Restricting Atrazine Use on Corn and Sorghum to Postemergent Applications

Atrazine is the most widely used herbicide for corn and sorghum and the most commonly encountered in ground and surface water. In addition to water quality problems, atrazine poses hazards through atmospheric transport, food residues, and exposure of applications and wildlife. If atrazine use is restricted, substitute herbicides will come into wider use, increasing the likelihood of occurrence of their own sets of potentially undesirable side effects and imposing cost or efficacy penalties

Agricultural Policies and Soil Degradation in Western Canada: An Agro-Ecological Economic Assessment - The Environmental Modeling System

An environmental modeling system is being constructed around the EPIC model that will be interfaced with an economic component (RS-CRAM) within an integrated modeling system to analyze agricultural policies such as GRIP for western Canada. A description of the major EPIC subcomponents is provided, including the most important data inputs. An environmental database also has been constructed for EPIC. This database consists of: (1) soil layer and landform data in separate databases for each Prairie Province, (2) ARA 31-year daily historical weather data (precipitation and maximum and minimum temperature) in EPIC format, (3) EPIC weather generator tables for each ARA, and (4) EPIC wind arrays for selected climate stations in Alberta, Manitoba, and Saskatchewan

Agricultural Policies and Soil Degradation in Western Canada: An Agro-Ecological Economic Assessment - The Integration of Enviornmental and Economic Components

This report describes the interface between RS-CRAM (resource sensitive Canadian Regional Agriculture Model) and the environmental components of the integrated modeling system for crops, crop sequences, and management systems representative of western Canadian agriculture. An experimentally designed set of EPIC (Erosion Productivity Impact Calculator) simulations were performed to generate erosion output that was then used to construct wind and water erosion metamodels (response functions) for several Canadian provinces

Agricultural Policies and Soil Degradation in Western Canada: An Agro-Ecological Economic Assessment

This report summarizes the major findings of a study in which an integrated agro-ecological economic modeling system was constructed around Agriculture Canada\u27s Canadian Regional Agriculture Model (CRAM) to analyze the economic and environmental impacts of proposed agricultural policies. The discussion covers the integrated modeling system and the policy analysis results, and presents future recommendations that emphasize how the current system can be improved

Agricultural Policies and Soil Degradation in Western Canada: An Agro-Ecological Economic Assessment - Modifications to CRAM and Policy Evaluation Results

Described in this report is the application of an integrated agro-ecological modeling system that has been constructed around Agriculture Canada\u27s Canadian Regional Agriculture Model (CRAM) to analyze the economic and environmental impacts of proposed agricultural policies for Alberta, Saskatchewan, and Manitoba. This integrated modeling system consists of an agricultural decision component and an environmental component