Nitrate Reduction Approaches

Resource /Energy Economics and Policy, Q25,

Hydrologic Simulations of the Maquoketa River Watershed Using SWAT

This paper describes the application of the Soil and Water Assessment Tool (SWAT) model to the Maquoketa River watershed, located in northeast Iowa. The inputs to the model were obtained from the Environmental Protection Agency\u27s geographic information/database system called Better Assessment Science Integrating Point and Nonpoint Sources (BASINS). Climatic data from six weather stations located in and around the watershed, and measured streamflow data from a U.S. Geological Survey gage station at the watershed outlet were used in the sensitivity analysis of SWAT model parameters as well as its calibration and validation for watershed hydrology and streamflow. A sensitivity analysis was performed using an influence coefficient method to evaluate surface runoff and baseflow variations in response to changes in model input hydrologic parameters. The curve number, evaporation compensation factor, and soil available water capacity were found to be the most sensitive parameters among eight selected parameters when applying SWAT to the Maquoketa River watershed. Model calibration, facilitated by the sensitivity analysis, was performed for the period 1988 through 1993, and validation was performed for 1982 through 1987. The model performance was evaluated by well-established statistical methods and was found to explain at least 86% and 69% of the variability in the measured streamflow data for the calibration and validation periods, respectively. This initial hydrologic modeling analysis will facilitate future applications of SWAT to the Maquoketa River watershed for various watershed analyses, including water quality

Hydrologic modeling and climate change study in the Upper Mississippi River Basin using SWAT

This dissertation describes the modeling efforts on the Upper Mississippi River Basin (UMRB) using the Soil and Water Assessment Tool (SWAT) model. The main goal of this study is to apply the SWAT model to the UMRB to evaluate the model as a tool for agricultural policy analysis and climate change impact analysis. A sensitivity analysis using influence coefficient method was conducted for eight selected hydrologic input parameters to identify the most to the least sensitive parameters. Calibration and validation of SWAT were performed for the Maquoketa River Watershed for streamflow on annual and monthly basis. The model was then validated for the entire UMRB streamflow and evaluated for a climate change impact analysis. The results indicate that the UMRB hydrology is very sensitive to potential future climate changes.;The impact of future climate change was then explored for the streamflow by using two 10-year scenario periods (1990s and 2040s) generated by introducing a regional climate model (RegCM2) to dynamically downscale global model (HadCM2) results. The combined GCM-RCM-SWAT model system produced an increase in future scenario climate precipitation of 21% with a resulting 50% increase in total water yield in the UMRB. Furthermore, evaluation of model-introduced uncertainties due to use of SWAT, GCM, and RCM models yielded the highest percentage bias (18%) for the GCM down scaling error.;Building upon the above SWAT validation, a SWAT modeling framework was constructed for the entire UMRB, which incorporates more detailed input data and is designed to assess the effects of land use, climate, and soil conditions on streamflow and water quality. An application of SWAT is presented for the Iowa and Des Moines River watersheds within the modeling framework constructed for the UMRB. A scenario run where conservation tillage adoption increased to 100% found a small sediment reduction of 5.8% for Iowa River Watershed and 5.7% for Des Moines River Watershed. On per-acre basis, sediment reduction for Iowa and Des Moines River Watersheds was found to be 1.86 and 1.18 metric tons respectively. Furthermore an attempt to validate the model for the entire UMRB yielded strong annual results

Allocating Nutrient Load Reduction across a Watershed: Implications of Different Principles

A watershed based model, the Soil and Water Assessment Tool (SWAT), along with transfer coefficients is used to assess alternative principles of allocating nutrient load reduction in the Raccoon River watershed in central Iowa. Four principles are examined for their cost-effectiveness and impacts on water quality: absolute equity, equity based on ability, critical area targeting, and geographic proximity. Based on SWAT simulation results, transfer coefficients are calculated for the effects of nitrogen application reduction. We find both critical area targeting and downstream focus (an example of geographic proximity) can be more expensive than equal allocation, a manifestation of absolute equity. Unless abatement costs are quite heterogeneous across the subwatersheds, the least-cost allocation (an application of the principle of equity based on ability) have a potential of cost savings of about 10% compared to equal allocation. We also find that the gap between nitrogen loading estimated from transfer coefficients and nitrogen loading predicted by SWAT simulation is small (in general less than 5%). This suggests that transfer coefficients can be a useful tool for watershed nutrient planning. Sensitivity analyses suggest that these results are robust with respect to different degrees of nitrogen reduction and how much other conservation practices are used.Environmental Economics and Policy,

Content-based Image Retrieval using Color and Geometry

The increased need of content based image retrieval technique can be found in a number of different domains such as Data Mining, Education, Medical Imaging, Crime Prevention, Weather forecasting, Remote Sensing and Management of Earth Resources. With the development of Multimedia data types and heavy increase in available bandwidth, there’s a huge demand of Image Retrieval system Content based image retrieval system uses color and geometry means to store, retrieve, sort and print any combinations of the images. The retrieval of images is, for the majority of search engines, available for collecting data from the image, this can be an image file name, html tags and surrounding text. This left the actual image more or less ignored. CBIR uses methods that analyze the actual bits and pieces i.e. color, shape, texture and spatial layout. There have been different approaches such as feature extraction, indexing and retrieval process. One approach is to make an attempt to classify the image into a more textual described context. With the image classified, it can be retrieved using more traditional and better retrieval methods. Our system Content Based Image Retrieval which is based on color and geometry, the system exactly does feature extraction in first step by using color, texture and shape (geometry) on images which gives there features which can be used to classify the image into different groups using distance formulas. Also the system gives relevant images as well as irrelevant images. The project thus going to work on relevance feedback of user which helps to improve the overall results

Level of watershed subdivision for water quality modeling

The size and number of subwatersheds can impact a watershed modeling process and subsequent results. The objective of this study was to determine the appropriate level of subwatershed division for simulating flow, sediment, and nutrient. The SWAT model with GIS interface (AVSWAT) was applied to four Iowa watersheds that varied greatly in drainage area. Annual output was analyzed from each simulation, which was executed for 31 years using climatic data representing the period of 1970 to 2000. It was found that the streamflow is not significantly affected by decrease in subwatershed scale, whereas sediment yields were directly related to subwatershed scale. The threshold subwatershed size, i.e. minimum size of a subwatershed at which variation due to different subdivisions tends to stabilize, was found to be around 3 percent of the total drainage area to adequately predict sediment yield. Decreasing the size of subwatersheds beyond this level does not significantly affect the computed sediment yield. Similar analysis on nitrate concentration found 2 percent of the total drainage area as threshold area. This threshold subwatershed size can be used to optimize SWAT input data preparation requirements and simplify the interpretation of results, without compromising simulation accuracy