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Water Parcel Tracking to Evaluate Conservation Practice Effectiveness in Agricultural Watersheds

Authors: Ryan Felton,  John Baker, Brent Dalzell, Joel Nelson, University of Minnesota

Abstract: In agricultural landscapes, differences in management practices, soil characteristics, and topography can all interact to influence the delivery of water, sediment, and nutrients from farm fields to receiving ditches and streams. While a wide variety of conservation practice options are available to landowners and conservation professionals, it can be difficult to know where they are most cost effective because of a disconnect in information between plot-scale studies and monitoring data collected at watershed outlets. In order to fill this knowledge gap, we are employing a Lagrangian sampling technique to monitor a water parcel as it travels down an agricultural ditch network. With this approach, the behavior of small scale watersheds can be characterized more precisely, and important sites of new inputs and/or transformations can be identified. Our sampling approach is based on a small inflatable kayak that is capable of navigating narrow, shallow agricultural ditches. From the kayak, we deploy a sensor platform consisting of a multiparameter sonde coupled with a GPS receiver which allows us to generate high-frequency data sets through a ditch and stream network. Preliminary results have been helpful for identifying the influence of key micro-watershed tributaries as important sources of nitrate, and assessing the role of wetlands in mediating nitrate loads. Ongoing efforts are focused on combining our Lagrangian sampling with Eulerian monitoring at selected sites in order to identify biogeochemically important hot-spots and hot-moments. Potential applications of this methodology include evaluation of the impact of specific practices such as saturated buffers and constructed wetlands on water quality as well as identifying areas of concern within small watersheds.