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USGS2004

Archive of digital boomer and chirp seismic reflection data collected during USGS Cruises 01RCE05 and 02RCE01 in the Lower Atchafalaya River, Mississippi River Delta, and offshore southeastern Louisiana, October 23-30, 2001, and August 18-19, 2002

In October of 2001 and August of 2002, the U.S. Geological Survey conducted geophysical surveys of the Lower Atchafalaya River, the Mississippi River Delta, Barataria Bay, and the Gulf of Mexico south of East Timbalier Island, Louisiana. This report serves as an archive of unprocessed digital marine seismic reflection data, trackline maps, navigation files, observers' logbooks, GIS information, and formal FGDC metadata. In addition, a filtered and gained GIF image of each seismic profile is provided. The archived trace data are in standard Society of Exploration Geophysicists (SEG) SEG-Y format (Barry and othes, 1975) and may be downloaded and processed with commercial or public domain software such as Seismic Unix (SU). Examples of SU processing scripts and in-house (USGS) software for viewing SEG-Y files (Zihlman, 1992) are also provided. Processed profile images, trackline maps, navigation files, and formal metadata may be viewed with a web browser. Scanned handwritten logbooks and Field Activity Collection System (FACS) logs may be viewed with Adobe Reader.

Louisiana↗

USGS2006

Quantifying the uncertainty in site amplification modeling and its effects on site-specific seismic-hazard estimation in the upper Mississippi embayment and adjacent areas

The Mississippi embayment, located in the central United States, and its thick deposits of sediments (over 1 km in places) have a large effect on earthquake ground motions. Several previous studies have addressed how these thick sediments might modify probabilistic seismic-hazard maps. The high seismic hazard associated with the New Madrid seismic zone makes it particularly important to quantify the uncertainty in modeling site amplification to better represent earthquake hazard in seismic-hazard maps. The methodology of the Memphis urban seismic-hazard-mapping project (Cramer et al., 2004) is combined with the reference profile approach of Toro and Silva (2001) to better estimate seismic hazard in the Mississippi embayment. Improvements over previous approaches include using the 2002 national seismic-hazard model, fully probabilistic hazard calculations, calibration of site amplification with improved nonlinear soil-response estimates, and estimates of uncertainty. Comparisons are made with the results of several previous studies, and estimates of uncertainty inherent in site-amplification modeling for the upper Mississippi embayment are developed. I present new seismic-hazard maps for the upper Mississippi embayment with the effects of site geology incorporating these uncertainties.

Bulletin of the Seismological Society of America↗

USGS2009

Water-Quality and Biological Assessment of the Iowa River and Tributaries Within and Contiguous to the Meskwaki Settlement of the Sac and Fox Tribe of the Mississippi in Iowa, 2006-07

In cooperation with the Sac and Fox Tribe of the Mississippi in Iowa (Meskwaki Nation), the U.S. Geological Survey conducted a 2-year baseline assessment of the chemical and biological quality of streams within the Meskwaki Settlement in central Iowa. The Meskwaki Nation is a federally recognized tribe that wishes to establish water-quality standards to safeguard the integrity of surface waters and aquatic biota within the settlement for the health and welfare of the tribal community. The settlement is drained by the Iowa River and four tributaries (Onion, Cattail, Raven, and Bennett Creeks). Water-quality samples were collected at three sites on the Iowa River, two sites on Onion Creek, and one site each on Cattail, Raven, and Bennett Creeks from April 2006 through July 2007. Biological and habitat assessments were conducted at all three sites on the Iowa River and the downstream-most site on Onion Creek from June through August 2007. Analysis of physical properties, major ions, nutrients, trace compounds, bacteria, and total suspended solids in water, and trace metals and organic compounds in streambed sediment provided information about the effects of anthropogenic (human related) activities on the water quality of settlement streams. Analysis of biological samples collected during the summer of 2007, including fish community, benthic macroinvertebrates, and periphyton samples, as well as physical habitat characteristics, provided information on the effects of water quality on the condition of the aquatic environment. The majority of surface water sampled within the settlement was predominately a calcium bicarbonate type. Nitrates (nitrate plus nitrite as nitrogen) exceeded the U.S. Environmental Protection Agency's (USEPA) primary drinking-water Maximum Contaminant Level of 10 ug/L in 19 of 36 samples from sites on the Iowa River and Raven and Bennett Creeks but not in samples from Onion and Cattail Creeks. None of the samples analyzed for pesticides, trace metals, wastewater, or fuel contaminants were found to exceed drinking-water regulations for the USEPA or State of Iowa targeted constituents. Bacteria densities for Escherichia coli (E. coli) ranged from less than 10 to more than 600,000 colony-forming units per 100 milliliters of water and were largest following intense rainfall runoff. The largest densities were recorded in samples collected from the tributaries, most notably from Cattail Creek downstream from the tribal headquarters area and Onion Creek downstream from the sewage lagoons. Arsenic and nickel concentrations in bottom sediment from Onion Creek exceeded the USEPA threshold effects level in a composite sample collected during the habitat assessment in July 2007. Suspended-sediment concentration was estimated in terms of total suspended solids. Overall, Onion and Bennett Creeks were the least turbid, whereas the ephemeral Cattail Creek had the most turbid samples. Aquatic-community data were collected at four sites on the Meskwaki Settlement during the summer of 2007 to provide a baseline biological assessment of stream conditions. This assessment was based on sampling of the fish, benthic macroinvertebrate, and periphyton communities along with physical habitat characteristics. Individual biological metrics were derived from the data collected during the community surveys. These metrics were used to calculate Indexes of Biological Integrity (IBIs). The calculated values from the IBIs provided a numerical value that was used to provide an assessment of the biological condition at each biological sampling site. The fish community samples indicated that all of the sampling sites would be considered in fair condition, with one exception being a collection site on the Iowa River at Highway 49 near Tama, Iowa, which was classified in poor condition. The benthic macroinvertebrate IBI indicated a classification of good for three of the four biological sampling sites, with the Iowa River near Montour, Iowa,

Scientific Investigations Report↗

USGS2003

Recalibration of a ground-water flow model of the Mississippi River Valley alluvial aquifer of northeastern Arkansas, 1918-1998, with simulations of water levels caused by projected ground-water withdrawals through 2049

A digital model of the Mississippi River Valley alluvial aquifer in eastern Arkansas was used to simulate ground-water flow for the period from 1918 to 2049. The model results were used to evaluate effects on water levels caused by demand for ground water from the alluvial aquifer, which has increased steadily for the last 40 years. The model results showed that water currently (1998) is being withdrawn from the aquifer at rates greater than what can be sustained for the long term. The saturated thickness of the alluvial aquifer has been reduced in some areas resulting in dry wells, degraded water quality, decreased water availability, increased pumping costs, and lower well yields. The model simulated the aquifer from a line just north of the Arkansas-Missouri border to south of the Arkansas River and on the east from the Mississippi River westward to the less permeable geologic units of Paleozoic age. The model consists of 2 layers, a grid of 184 rows by 156 columns, and comprises 14,118 active cells each measuring 1 mile on a side. It simulates time periods from 1918 to 1998 along with further time periods to 2049 testing different pumping scenarios. Model flux boundary conditions were specified for rivers, general head boundaries along parts of the western side of the model and parts of Crowleys Ridge, and a specified head boundary across the aquifer further north in Missouri. Model calibration was conducted for observed water levels for the years 1972, 1982, 1992, and 1998. The average absolute residual was 4.69 feet and the root-mean square error was 6.04 feet for the hydraulic head observations for 1998. Hydraulic-conductivity values obtained during the calibration process were 230 feet per day for the upper layer and ranged from 230 to 730 feet per day for the lower layer with the maximum mean for the combined aquifer of 480 feet per day. Specific yield values were 0.30 throughout the model and specific storage values were 0.000001 inverse-feet throughout the model. Areally specified recharge rates ranged from 0 to about 30 inches and total recharge increased from 1972 to 1998 by a factor of about four. Water levels caused by projected ground-water withdrawals were simulated using the calibrated model. Simulations represented a period of 50 years into the future in three scenarios with either unchanged pumpage, pumpage increased by historic trends, or pumpage increased by historic trends except in two areas of the Grand Prairie. If pumping remains at 1997 rates, this produces extreme water-level declines (areas where model cells have gone dry or where the water level in the aquifer is equal to or less than the original saturated thickness, assuming confined conditions in the aquifer everywhere in the formation in predevelopment times) in the aquifer in two areas of the aquifer (one in the Grand Prairie area between the Arkansas and White Rivers and the other west of Crowleys Ridge along the Cache River) with about 400 square miles going dry. Increasing the pumping rates to that which would be projected using historic data led to increased extreme water-level declines in both areas with about 1,300 square miles going dry. Declines in both scenarios generally occurred most rapidly between 2009 and 2019. Reducing the pumping rates to 90 percent of that used for projected historic rates in areas between the Arkansas and White Rivers relating to two diversion projects of the U.S. Army Corps of Engineers and other agencies did little to decrease the extreme water-level declines. However, these pumpage reductions are small (amounting to about 16 percent of the reductions that could result from implementation of these diversion projects).

Water-Resources Investigations Report↗

USGS2013

Streamflow characterization and summary of water-quality data collection during the Mississippi River flood, April through July 2011

From April through July 2011, the U.S. Geological Survey collected surface-water samples from 69 water-quality stations and 3 flood-control structures in 4 major subbasins of the Mississippi River Basin to characterize the water quality during the 2011 Mississippi River flood. Most stations were sampled at least monthly for field parameters suspended sediment, nutrients, and selected pesticides. Samples were collected at daily to biweekly frequencies at selected sites in the case of suspended sediment. Hydro-carbon analysis was performed on samples collected at two sites in the Atchafalaya River Basin to assess the water-quality implications of opening the Morganza Floodway. Water-quality samples obtained during the flood period were collected at flows well above normal streamflow conditions at the majority of the stations throughout the Mississippi River Basin and its subbasins. Heavy rainfall and snowmelt resulted in high streamflow in the Mississippi River Basin from April through July 2011. The Ohio River Subbasin contributed to most of the flow in the lower Mississippi-Atchafalaya River Subbasin during the months of April and May because of widespread rainfall, whereas snowmelt and precipitation from the Missouri River Subbasin and the upper Mississippi River Subbasin contributed to most of the flow in the lower Mississippi-Atchafalaya River Subbasin during June and July. Peak streamflows from the 2011 flood were higher than peak streamflow during previous historic floods at most the selected streamgages in the Mississippi River Basin. In the Missouri River Subbasin, the volume of water moved during the 1952 flood was greater than the amount move during the 2011 flood. Median concentrations of suspended sediment and total phosphorus were higher in the Missouri River Subbasin during the flood when compared to the other three subbasins. Surface water in the upper Mississippi River Subbasin contained higher median concentrations of total nitrogen, nitrate, orthophosphate, and atrazine during the flood period.

Mississippi River Basin↗

USGS1999

Evidence of Climate Change over the Last 10,000 Years from the Sediments of Lakes in the Upper Mississippi Basin

The study of lake sediments as recorders of past climate change has been a major focus of the Geologic Division's Global Change and Climate History Program. In particular, lakes of the Upper Mississippi Basin (UMB) provide some of the most detailed records of climate and environmental change during the Holocene (last 10,000 years). The UMB is particularly sensitive to climate change because the three airmasses that control the climate of North America (fig. 1) intersect here.

Fact Sheet↗

USGS1979