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Hydraulic functions of retention devices in natural large rivers have been studied. An evaluation of detention devices formed due to side channels, islands, backwaters, and stump fields within the Upper Mississippi Pools has shown that these are quite significant and in some cases these detention areas within the channel borders can occupy as much as 75 to 93% of the total surface area. A large eddy on the order of the width of the Mississippi River in Pool 19 is used to illustrate the travel time in the hydraulic retention areas.
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The performance of two popular watershed scale simulation models – HSPF and SWAT – were evaluated for simulating the hydrology of the 5,568 km2 Iroquois River watershed in Illinois and Indiana. This large, tile drained agricultural watershed provides distinctly different conditions for model comparison in contrast to previous studies. Both models were calibrated for a nine-year period (1987 through 1995) and verified using an independent 15-year period (1972 through 1986) by comparing simulated and observed daily, monthly, and annual streamflow. The characteristics of simulated flows from both models are mostly similar to each other and to observed flows, particularly for the calibration results. SWAT predicts flows...
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Excess sediment and nutrients including nitrogen and phosphorus are major causes of non-point source (NPS) pollution in rivers and streams draining agricultural watersheds. Research studies indicate that a significant proportion of NPS pollutants entering the Mississippi River comes from agricultural watersheds in the Midwest. Illinois watersheds are among those that contribute the highest nutrient flux to the Gulf of Mexico. Watershed Best Management practices (BMPs) could serve as crucial control measures in reducing NPS pollutants from agricultural watersheds and have been applied in many places in Upper Mississippi River basin. This paper presents a coupled optimization-watershed model designed to identify cost-effective...
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A large percentage of the annual sediment yield from a watershed is transported by a stream during a small number of floods that occur in a relatively short period of time in a year. The sediment load during flood events are examined and relations between the annual sediment yield and the sediment load during the major floods in a given year are developed based on available stream sediment data from the state of Illinois. On the average, the annual flood transports from 20 percent (for large rivers) to 23 percent (for small streams) of the annual sediment load, while the two highest floods in a year transport from 32 to 43 percent of the annual sediment load. The average duration of the annual flood is only 9.2...
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