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Watershed-Scale Evaluation of BMP Effectiveness and Acceptability: Eagle Creek Watershed, Indiana


Project Overview: This hypothesis driven research effort will focus on the Eagle Creek Watershed because of its importance as the drinking water supply for Indianapolis, availability of data about water quality, strong existing monitoring programs, and our close ties to the watershed alliance. We have proposed three hypotheses to underpin our efforts and also make the work applicable to other locations:<P> H1: Different conservation mosaics (consisting of the selection, mix, location, timing, and maintenance of conservation practices) have measurable and differential impacts on water quality entering the Eagle Creek watershed. Not all conservation mosaics perform similarly. Some outperform others.<P> H2: Among the group of conservation mosaics that are deemed effective in improving water quality entering the Eagle Creek watershed, some conservation mosaics are more cost-effective than others.<P> H3: Among the group of conservation mosaics that are deemed cost-effective in improving water quality entering the Eagle Creek watershed, some conservation mosaics are more acceptable to land managers than others. <P> In order to test these hypotheses the study is developed around four objectives: <P>Objective 1. Determine the effectiveness of existing and potential conservation practices in Eagle Creek watershed at reducing atrazine, phosphorus, nitrogen (NO3), E. coli and sediment entering the reservoir: This objective will address Hypothesis 1 and Question 1 and 2 of the call. <P>Objective 2. Determine the social acceptability of potential conservation practices - This objective will address Hypothesis 2 and 3 and Question 3 of the <P>call. Objective 3. Determine the economic profile of potential conservation practices - This objective will address Hypothesis 2 and 3 and Question 3 of the call <P>Objective 4. Use the results to provide conservation agencies with information they can use to better target cost-share dollars and outreach strategies. This objective will address Question 4 of the call

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Non-Technical Summary: Over the last 30 years, the implementation of best management practices (BMPs) has been a mainstay of conservation programs designed to improve water quality while maintaining agricultural productivity. While the value of BMPs can be demonstrated at the small scale, the aggregated effects across a watershed are undocumented. This project integrates a watershed investigation with a social and economic benefits analysis and education program by bring together experts in modeling, social sciences, and economics with a research group managing both historical data and ongoing watershed sample collections. Our target watershed is the 77,000 acre Eagle Creek Watershed north of Indianapolis, which feeds into Eagle Creek and the city's major storage reservoir supplying water to 780,000 residents. In spite of the use of BMPs, water quality in the watershed has continued to decline. Our effort has two purposes: the first is to analyze and model an extensive water quality database for the watershed so that we can correlate trends in water quality with current BMPs and then using modeling, compare the trends in water quality to what would be achieved if different BMP management approaches were used. The second purpose of the project is to develop an understanding of the social and economic limitations to the adoption of BMPs and by analyzing the current social limitations to acceptance of water quality management alternatives devise strategies to accelerate positive change. In essence, we will use real data to drive scenario modeling as a means to inform our educational programs. <P> Approach: Task 1: Subwatershed water quality assessment using Longitudinal Yield (Quantitative) and Threshold Exceedence (Qualitative) approaches. Step 1: Subwatershed Characterization: Subwatersheds will be characterized according to land-use/land cover changes from 1995 to 2003 to provide a matching data set to the water quality data. While the assessment will be focused on accounting for yearly changes in BMP implementation, location, and area, other confounding land-use/land cover (e.g., land-use perturbation, impervious surfaces, point sources and CAFO, and unsewered community and septic system distribution). Step 2: Subwatershed Water Quality Assessment: Water quality data sets will then be analyzed according to the following methods. Step 3: Analysis of Relationships Between Subwatershed Characterization and Water Quality: Once each subwatershed has been assigned a measurement of water quality for each year (Step 2), changes in water quality will be analyzed against changes in BMP implementation (location and area) and other confounding watershed land-use/landcover changes. Task 2: Analysis of the effectiveness of existing BMPs using the SWAT model Task 1 will provide an estimate of the impact of BMPs on water quality by comparing observed water quality and watershed characteristics. However, it will not allow us to extend the analysis to other BMPs that were not installed, or address questions about the impact of BMP location and timing on effectiveness. In order to ask "what if?" questions, we will use the SWAT watershed model, applying two modeling approaches to strengthen the analysis. Approach A is deterministic, in which the model will be calibrated to find the single best set of parameters, validated using a different time period, and then used in prediction (the "calibrate-validate-predict" approach). Approach B is probabilistic, which acknowledges the uncertain nature of model parameterization, and uses a range of parameters to predict probabilities of various outputs. Task 3: Evaluate the significance of type, placement, and timing on performance of potential BMPs To evaluate the aggregated performance of BMP strategies and mixes we will use the calibrated parameters from Task 2 to simulate a suite of landscape mosaics for the Eagle Creek Watershed. We define a landscape mosaic to be a spatially-explicit BMP overlay on the watershed map. This mosaic may reflect considerations of BMP mix, location, size, scope, and degree of maintenance. Some landscape mosaics may consist of a single BMP (e.g. buffer strips) applied to defined class of land.

Turco, Ronald
Purdue University
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