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Instrumentation and Sampling Strategies for Monitoring Small Watersheds in Illinois

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Paper number  032049,  2003 ASAE Annual Meeting . (doi: 10.13031/2013.13764) @2003
Authors:   James A. Slowikowski, Amy M. Russell, Kip E. Stevenson, Ted E. Snider
Keywords:   Monitoring, data collection, nutrients, sediment, streamflow

Beginning in 1999, the Illinois State Water Survey (ISWS) established thirteen sediment and nutrient monitoring stations on ten watersheds to assist with several watershed management programs that were being initiated by the Illinois Department of Natural Resources (IDNR). This intensive watershed monitoring program is designed to collect hydrologic, sediment and nutrient data in sufficient resolution to reflect the effects of changes in land use within the watershed over time. These watersheds are predominantly agricultural and range in area from 8.4 miles2 (21.8 km2) to 66.4 miles2 (172 km2). Streams are characterized by rapid changes in stage, high sediment concentrations and heavy debris flows. Monitoring stations utilize H2OFX pressure transducers, Campbell Scientific CR10x dataloggers and ISCO 6700 pump samplers. Data collection includes continuous records of stage, sufficient discharge measurements to define the rating curves for these dynamic streams, suspended sediment samples and nutrient samples analyzed for: nitrate-N, nitrite- N, ammonium-N, total Kjeldahl nitrogen, orthophosphate, total phosphorus and total dissolved phosphorus. Precipitation data are also collected for each watershed. Automated sampling driven by changes in the stream hydrograph is used to bolster the manual sampling during storm events. On average, nearly 100 discharge measurements, 200 nutrient samples and 900 sediment samples have been collected at each monitoring station. This paper presents the challenges of gaging/monitoring small streams and offers potential solutions by describing the instrumentation and logic behind the automated and manual sampling used to obtain the desired data resolution and the procedures used for data management. Additionally the quality assurance/quality control (QA/QC) measures employed for both data collection and reduction are described. As the period of record for these stations increases, these datasets will not only help evaluate the effects of land use practices on sediment and nutrient loadings, but will also offer valuable insight into small watershed hydrology.

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