Perceptions of Irrigation Water Management Practices in the Mississippi Delta

The Mississippi River Valley Alluvial Aquifer (MRVAA) is being depleted, and practices that improve water stewardship have been developed to reduce drawdown. This study assesses how Mississippi Delta producers changed their perceptions of these practices over time. The analysis employs data from two surveys carried-out in 2012 and 2014 of all Mississippi permittees who held an agricultural well permit drawing from the MRVAA. Focusing on water-saving practices, this study found that producer perception of the usability of flowmeters improved over time. About 80% and 90% more producers growing corn and soybeans, respectively, felt that computerized hole selection was highly efficient. In 2014, 38% of corn and 35% of soybean producers believed that shortened furrow length was a highly efficient practice—up from 21% in corn and 24% in soybean producers in 2012. Approval of irrigation automation, moisture probes, and other irrigation technology rose from 75%of producers in 2012 to 88% by 2014. Favorability toward water-saving practices increased overall between the survey years.

Hydrodynamics in the Morganza Floodway and Atchafalaya Basin, report 3 : phase 3; a report for the US Army Corps of Engineers, MRG&P

The Morganza Floodway and the Atchafalaya Basin, located in Louisiana west of the Mississippi River, were evaluated using a two-dimensional Adaptive Hydraulics model. Prior to this study, Phase 1 and 2 model studies were performed that indicated that the existing floodway may not be able to pass the Project Design Flood discharge of 600,000 cubic feet per second due to levee overtopping. In this study, all elevations of exterior and interior levees were updated with current crest elevations. In addition, the Phase 3 effort evaluated the sensitivity of the floodway’s flow capacity to variations in tree/vegetation density conditions. These adjustments in roughness will improve the understanding of the role of land cover characteristics in the simulated water surfaces. This study also provides a number of inundation maps corresponding to certain flows through the Morganza Control Structure.

Vertical and horizontal datums used in the Lower Mississippi Valley for US Army Corps of Engineers projects

Six geodetic datums have been used by the US Army Corps of Engineers (USACE), Mississippi River Commission (MRC), for river surveys in the Lower Mississippi Valley (LMV). These legacy elevation datums are the Cairo datum, the Memphis datum, the Mean Gulf Level (MGL), the Mean Sea Level (MSL), the National Geodetic Vertical Datum (NGVD) 1929, and the North American Vertical Datum 1988 (NAVD88). The official geodetic datum currently prescribed by the USACE is NAVD88 (USACE 2010). In addition to these different geodetic datums, hydraulic datums are in use by the USACE for rivers, lakes, and reservoir systems. Hydrographic surveys from the Mississippi River are typically based on a low water pool or discharge reference, such as a low water reference plane (LWRP), an average low water plane (ALWP), or a low water (LW) plane. The following technical note is intended to provide background information about legacy datums used in the LMV to permit comparison of historic maps, charts, and surveys pertaining to the Mississippi River in the LMV. The purpose of this report is to provide background information and history of different published horizontal and vertical datums used for presentation of hydrographic survey data from the Mississippi River. The goal is to facilitate understanding of differences with comparison to other historic surveys for change-detection studies along the river. Conversion values are identified herein for the earlier surveys where appropriate, and methods are presented here to evaluate the differences between earlier and later charts and maps. This report is solely intended to address the LMV area and historic surveys made there. This note is not applicable to areas outside of the LMV. Throughout this technical note, historic hydrographic surveys and data from the Memphis, TN, to Rosedale, MS, reach will be used as examples of features of interest for discussion purposes. Selected historic hydrographic survey sheets at Helena, AR, are included as Plates 1 to 3 (Appendix C) of this document and will be used as examples for discussion purposes.

Intended Ignorance: The Collapse of the I-35 W Mississippi River Bridge on 1 August 2007

At 6:05 PM on 1 August 2007, the I-35 W Highway Bridge crossing the Mississippi River in Minneapolis, Minnesota, collapsed due to the failure of crucial parts of the bridge’s steel truss structure. Thirteen people died in the disaster, 145 were injured. A report of United States National Transportation Safety Board (NTSB) revealed that the Minnesota Department of Transport, over a long period of time, had ignored available information about the structurally deficient status of the bridge in anticipation of ‘budget busting’ repair costs. Which resulted in a preference for less expensive patch-up measures to improve the drivability of the bridge rather than a retrofit of the fracture-critical components of the steel truss whose failure triggered the disaster of 1 August 2007.

Influence of Key Environmental Drivers on the Performance of Sediment Diversions

A Delft3D morphodynamic model for Barataria Bay, Louisiana, USA is used to quantify a plausible range of land change in response to a proposed sediment diversion under a range of environmental drivers. To examine the influence of environmental drivers, such as Mississippi River water hydrographs, mineral and organic sediment loading, sea level rise rates, subsidence, and a projected implementation (or operation) date, 240 multi-decadal (2020–2100) numerical experiments were used. The diversion was assumed to begin operation in 2025, 2030, or 2035. The experiments revealed persistent benefits of the sediment diversion through 2100. Start data of 2025 result in a median net positive land change of 32 km2 by 2100; whereas the 90th, and 10th percentiles are 69 and 10 km2. A delay in the operation date of the diversion to 2030 or 2035 would reduce the net positive land change by approximately 15–20% and 20–30%, respectively.

A Quantitative Review of Irrigation Development in the Yazoo–Mississippi Delta from 1991 to 2020

The Yazoo–Mississippi Delta is one of the regions within the Lower Mississippi River Basin where substantial irrigation development and consequent groundwater depletion have occurred over the past three decades. To describe this irrigation development, a study was conducted to analyze existing geospatial datasets and to synthesize the results with those of past government surveys. The effort produced a quantitative review characterizing three aspects of irrigation development from 1991 to 2020. First, the expansion of irrigated area was tracked in terms of absolute area and in terms of fraction relative to total land or cropland area. Second, trends in irrigated land cover were traced in terms of irrigated crop mix, irrigated fractions of main crops, and comparisons with non-irrigated land. Third, changes in irrigation systems were examined in terms of water sources, energy sources, and application methods. Original findings of this study for the end of 2020 included moderate positive spatial autocorrelation in the density of irrigated areas; a higher irrigated crop preference for soybean and rice over cotton and corn in highly hydric soils; and 91% and 3% of permitted areas studied being respectively under groundwater withdrawal permits exclusively and under surface water diversion permits exclusively. By compiling such information, this paper can serve as a convenient reference on the recent history and status of irrigation development in the Yazoo–Mississippi Delta.