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Flooding in the Mississippi basin has become increasingly uncertain, and a succession of progressively higher, peak annual water levels is observed at many sites. Many record levels set in the central USA by the huge 1993 flood have already been superseded. Methodology developed elsewhere that recognizes trends of river stages is used to estimate present-day flood risk at 27 sites in the Mississippi basin that have >100 years of continuous stage record. Unlike official estimates that are fundamentally based on discharge, this methodology requires only data on river stage. A novel plot linearizes the official flood levels that are indirectly derived from the complex, discharge-based calculations and demonstrates that the neglect of trends has resulted in the effective use of undersized means and standard deviations in flood risk analysis. A severe consequence is that official 'base flood' levels are underestimated by 0.4 to 2 m at many sites in the central USA. [ABSTRACT FROM AUTHOR]

Data from the 1803–1806 Lewis and Clark expedition and nineteenth century stage records are used to quantitatively benchmark natural, premanagement hydrology of the lower Missouri River and assess the magnitude and timing of hydrologic change over nearly two centuries. Data show doubling in daily stage variability from the nineteenth century to 2005. Annual maximum stages have, at some sites, become more extreme, and their seasonality is less regular. Observed changes adversely affect riverine habitat and flood levels; their timing, beginning as early as 1900, suggests that channelization is the major driver. [ABSTRACT FROM AUTHOR]

Weldon Spring is consistently enriched in 18 O relative to other karst springs in east-central Missouri and western Illinois, suggesting an evaporated source component. Regional potentiometric head maps of the shallow aquifer suggest that Prairie Lake, an artificial lake built between 1954 and 1982, could represent this component. Isotopic, biological and chemical tracing of the spring conclusively verify the hypothesis that this lake has impacted Weldon Spring. Mixing calculations indicate that Weldon Spring is now comprised of approximately 80% lake water and 20% groundwater. Recent measurements indicate that the discharge rate of the spring is now approximately 10 times the rate prior to the construction of the lake, confirming the augmentation of flow by a new source. Analysis of the isotopic trends indicates that the subsurface travel time is short, and suggests that the conduits connecting the lake and the spring may be progressively enlarging. [ABSTRACT FROM AUTHOR]

The article presents statistics related to public safety and flood events in the United States.

Editorial. Comments on the nitrate contamination of surface water and groundwater in the U.S. Excess nitrates produced by fertilizer use; Effect of nitrates on water quality; Evidence of excess nitrates becoming nonpoint source pollution.