Chemical and Physical Characteristics of the Missouri River, Nebraska

Selected physical and chemical parameters were observed at the following sites: unchannelized and channelized main-channel Missouri River, an unchannelized backwater, and 13 tributaries of the Missouri River during the period 1985 through 1988. Mean main-channel discharge is artificially maintained at a higher rate during winter since construction of the main-stem dams. The mean flow through a remnant backwater in an unchannelized reach represents about 3.1% of the main-channel discharge. Turbidity is much reduced from the pre-dam period and is highest during the March and June periods of high discharge. Specific conductance in the main channel was measured as high as 955 umhos/cm-1 Water quality parameters are similar for unchannelized and channelized sites, although organic matter, as measured by total organic carbon and fine and coarse particulate organic matter, is higher as one proceeds downriver. The water quality of the unchannelized reach backwater basically reflects the water quality of the main channel, except that dissolved oxygen is reduced in some locations within the backwater and total chlorophyll values are double those found in the main channel. Tributary water quality is highly variable and most observed values were higher than main-channel values near these tributaries. Continued observations will help explain the role that tributary run-off plays in main-channel water quality as samples are acquired during run-off events such as flooding. We have hypothesized that the Missouri River may have been one of the most productive ecosystems in temperate North America. Additional research into carbon/nutrient dynamics and the mechanism through which this energy reached the aquatic system is necessary to substantiate this hypothesis