R2003-129 AUTHORIZING AGREEMENT - Laserfiche WebLink

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to year with changes in nitrate-N concentration and streamflow. Flow-weighted nitrate-N concentrations have been increasing during the study period at the Monticello station. Based on the first six years of monitoring, the Illinois State Water Survey has developed a model (Mazkus, M., Tsai, C.W.-S. et al. 2003) to forecast nitrate-N concentrations in Lake Decatur using previous and current nitrate levels in the lake. This tool will be valuable for management of the ion exchange facility operated by the City of Decatur. � , In order to best evaluate any ongoing and future lake and watershed management issues, continued monitoring is recommended. The additional data will enhance the baseline data � established in the watershed and detect any changes or trends in nitrate-N levels in the watershed. PROJECT OBJECTNES The main goal of this project is to collect reliable data throughout the Lake Decatur watershed for use by City of Decatur planners and resource managers to develop lake and watershed management alternatives based on scientific data. To accomplish this goa1, the following objectives are outlined: 1. Continue to maintain and operate watershed monitoring stations. Figure 1 shows the stations being monitored by the City of Decatur and Table 1 presents the City o� Decatur monitoring stations with the proposed sampling schedule. The Illinois State Water Survey will maintain the continuous stream recording equipment and the data records will be processed to determine continuous stream flows. Nitrate-N will continue to be sampled at the sites listed in Table 1. This sampling schedule will provide the data needed to quantify the amount of nitrates being contributed to Lake Decatur from the watershed. 2. Collect additional data: Samples will be collected for sediment, pH, and azsenic analyses. Table 1 presents the stations and sampling schedule. These parameters are important to the city for managing other aspects of Lake Decatur and drinking water supply. The sediment samples will be collected weekly and during several storms for analysis at the ISWS Sediment Laboratory. T'he pH will be measured on-site using a portable field meter. The arsenic samples will be collected approximately 20 times on a bi-weekly basis for analysis at the ISWS Analytical Chemistry and Technology Unit(ACTi�. 2