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Reducing Irrigation Return Flow Contributions to Rural Drinking Water Supply and Drainage to the Yellowstone River


Research and associated data collection objectives include characterizing and quantifing the effects of improved water-conveyance and Best Engineering Practices within the Buffalo Rapids watershed on the quantity and quality of irrigation return flow discharged to the Yellowstone River, quality of leachate to shallow alluvial ground water, and quantity of water withdrawn from the Yellowstone River. <P>The second objective is to develop a modeling framework based on Bayesian uncertainty and sensitivity analysis using the watershed-scale Soil and Water Assessment Tool (SWAT). We will determine the minimum information or data required to constrain the model predictive uncertainty to enable assessment of the effects of watershed management practices. We will then use the SWAT modeling framework developed and a comparative study of paired sub-watersheds to quantify the effects of implementation of prioritized BEPs/BMPs within the Buffalo Rapids watershed on quality of shallow ground water and irrigation drainage.<P> The extension objectives of the project are to test 90% of domestic water supply wells within the district through the Montana State University Well Educated program, to demonstrate to at least 70% of the irrigators the economic and environmental benefits that can be achieved through adoption of currently available BMPs and BEPs, and to train the Buffalo Rapids watershed group in water quality monitoring techniques that will allow for periodic assessment of BMP and BEP effectiveness and pollutant loading to the Yellowstone River. <P>The educational objectives of the project include developing educational resources based on Buffalo Rapids Irrigation District for graduate on-line courses, developing science education tools and for MSU undergraduate course LRES 110, and mentoring undergraduates in an earth science field through a summer intern program. Additionally, graduate students will be trained in scientific method and project development including data collection and watershed monitoring, watershed modeling, and soil water transport processes. Lastly, through collaborative efforts with the Montana Watercourse, we will work with local high school science classes to train teachers and students in developing a voluntary water quality monitoring program with emphasis on data collection protocol and data significance. <P>At project completion, peer reviewed journal manuscripts will be developed highlighting the overall project results, successes, limitations, and potential for extrapolation of the approach to other watershed communities in Montana and Northern Plains and Mountains region.

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Non-Technical Summary: To address issues of increased demands on water supplies and water quality degradation within the Buffalo Rapids Irrigation District of eastern Montana, irrigation management Best Engineering Practices (BEPs) and Best Management Practices (BMPs) have been implemented. However, limited validation exists of water quality improvements resulting from these efforts, limiting confidence in adoption by some irrigators. Lack of baseline and impact data restricts opportunity to insure BEPs and BMPS have or will contribute to improved water quality. The purpose of the project is to 1) improve the quality of the lower Yellowstone River by reducing agriculturally derived impairments to the River and groundwater of the watershed, 2) protect human health and drinking water by improving the quality of existing domestic water supplies, 3) insure sustainability of irrigated agriculture within the watershed, and 4) enhance water quality and quantity protection and soil conservation within the watershed. <P> Approach: Specific hydrologically isolated management units have undergone extensive conversion from earthen lateral canals and delivery ditches to closed pipe delivery. Three of these sub-watersheds, along with three companion sub-watersheds which have not undergone conversion to closed delivery systems, will be inventoried through soil sampling and shallow ground water sampling. Existing and collected surface water, ground water, and irrigation drainage data will be used to apply metrics to nutrient, sediment, and bacterial concentrations and loading to deep percolation, lateral seepage to irrigation drains, ground water quality, drain water quantity and quality, and loading to the Yellowstone River. The Soil and Water Assessment Tool (SWAT) will be implemented to assess the impact of watershed management practices on water quality and quantity in the Buffalo Rapids watershed. The model will be specified using Bayesian statistical inference. The model simulation will allow analysis of the effectiveness of existing management practices and identification of future priority sites for BEP/BMP implementation. The developed framework will provide a powerful predictive tool for assessing the likely results of future management decisions. To demonstrate impacts of the project, several evaluation tools will be implemented. Initially, a front-end needs assessment survey will be conducted. District managers and irrigators will be evaluated for perceived needs and concerns regarding BMP and BEP irrigation practices throughout the district. Formative evaluations will be implemented to assess steps in achieving project goals and objectives. Final phase project evaluations will be composed of summative assessments at project completion and through follow-up assessments. Longevity of behavioral change will be assessed through post-then-pre evaluation methods. MSUEWQ will strive to test 90% or more of the wells within the district through the Well Educated program. Subsidized testing for NO3-N, TDS, sodium, and bacteria will be contracted through a private laboratory. Test results will be interpreted and presented to participants. To assist in promoting change throughout the irrigation district, BMP/BEP benefits will be demonstrated through one day field tours of demonstration sites to at least 70% of the irrigators within the watershed. A water quality monitoring workshop will be conducted for community members and educators. Area high school teachers will be trained to develop a volunteer water quality monitoring program. Project managers will develop an education module based on Buffalo Rapids Irrigation District for Master of Science and Science Education graduate courses. Through the Land Resources and Environmental Sciences graduate program, a graduate student will be responsible for collection and assemblage of historical data and for the modeling methodology and outputs.

Bauder, Jim
Montana State University Extension Service
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