2023 Nebraska Water Leaders Academy

Eighteen participants completed the 2023 Water Leaders Academy bringing the total number of graduates to 186 since the inception of the program in 2011. Assessments of participants’ transformational leadership skills, champion of innovation skills, water knowledge, engagement with water issues, civic capacity, entrepreneurial leadership behaviors, boundary spanning skills, and curiosity increased significantly over the course of the year, according to both the participants and their raters. Feedback from the participants was highly positive and constructive. Academy planners are addressing participant concerns. Results of the program assessment indicate that the curriculum is meeting the Academy’s objectives. Therefore, only minor changes are planned for the 2024 Academy curriculum. The continued emergence of Academy alumni as leaders worldwide attests to its ongoing success

Exhumed fluvial landforms reveal evolution of late Eocene– Pliocene rivers on the Central and Northern Great Plains, USA

Cenozoic strata on the Great Plains are the products of a long- lived, continental sediment routing system, and yet strikingly little is known about these ancient rivers. This article details the discovery of ~3100 fluvial ridges—erosionally inverted alluvial- fan, channel- fill, channel- belt, and valley- fill deposits—extending from the Rocky Mountain front to the eastern margin of the Great Plains. The direct detection of these channel bodies reveals new insights into late Eocene– Pliocene drainage evolution. Late Eocene– Oligocene streams were morphologically diverse. Alluvial fans adjacent to the Rocky Mountain front changed eastward to parallel or downstream- divergent, fixed, single- thread, straight to slightly sinuous (S = 1.0– 1.5) streams \u3c50 m in width. At ~100 km from the Rocky Mountain front, streams became sinuous and laterally mobile, forming amalgamated channel bodies as much as 3 km in width. Streamflow in all these systems was highly dispersed (southeast to northeast) and temporally variable. These characteristics reveal a nascent Great Plains alluvial apron hosting small, poorly integrated drainages undergoing abrupt changes. By the Miocene, more uniform streamflow generally trended east- northeast. Channel deposits are identifiable 500 km from the Rocky Mountain front. Middle Miocene valley fills gave way to fixed, multithread channels a few kilometers in width by the late Miocene. These patterns evince a mature alluvial apron hosting bigger rivers in well- integrated drainages. We interpret the systematic changes between fixed and mobile channel styles to record spatially and temporally variable aggradation rates. The widening of channels in the late Miocene likely reflects increased discharge relating to wetter climates upstream or the integration of once- isolated Rocky Mountain drainage basins into a continental- scale drainage system

New Insights into Carboniferous Cyclothems. The Fourth Biennial Field Conference of the American Association of Petroleum Geologists (AAPG) Midcontinent Section Fourth Biennial Field Conference Abstracts and Guidebook

The term “cyclothem” was coined by Wanless & Weller (1932) to describe repetitive stratigraphic successions of Carboniferous age in Illinois. Nonetheless, comparable rhythmicity had been identified in Carboniferous rocks both in the central and eastern USA, and in Europe during the preceding century. Cyclothems were found to comprise repetitive vertical successions of sandstones, heterolithic (thinly interbedded) sandstones and mudrocks, mudrocks, limestones, and coals, in many cases with pedogenic overprinting of these lithologies. As usage of the term “cyclothem” increased, so did the diversity of successions to which the term was applied, to the point where many geologists advocated abandonment of the expression. An example of this misuse was the modified term “continental cyclothem”, used to describe alternations of coarse- and fine-grained alluvial and other strata. Using the term “cyclothem” to describe essentially non-cyclic, binary arrays of lithologies is here considered a retrograde step, as it introduces confusion as to what a cyclothem is and represents geologically. The original definition of “cyclothem” as an alternation of marine and nonmarine lithologies, however, is a robust and useful concept, and by this definition cyclothems are largely confined to Carboniferous and Permian systems in the paleotropics of North America and Europe. Their stratigraphic range broadly coincides with the timing of the late Paleozoic Ice Age, and many researchers have postulated that they are a record of eustatically-controlled rises and falls in sea-level associated with waxing and waning of Gondwanan ice centers. We propose a restricted definition of “cyclothems” that is limited to successions that were deposited (1) on low-gradient pericontinental shelves in paleotropical regions, (2) as far-field products of Gondwanan glacial growth and decay at various timescales, and (3) under conditions of low sediment supply in most cases (Fig. 1). As such, they are important archives of late Paleozoic paleoenvironmental change, and the concept can be used in a number of ways. For example, the onset of a cyclothemic motif in stratigraphic successions of late Visean age across Euramerica has been used to infer the onset of the main phase of glaciation in Gondwana. Cyclothems are also important as hosts for economic mineral resources, including oil and gas, coal, lime, water, and base and precious metals. This symposium introduces Field Conference participants to the nature and variety of cyclothems, and their geology. Papers concern aspects of cyclothems in numerous states of the USA from Illinois in the east to Utah in the west, and from Montana in the north to Texas in the south. Papers describe the stratigraphy, sedimentology, and resource geology of Carboniferous cyclothemic successions, including numerous petroleum-prospective regions and plays. The Field Excursion will allow participants to view well-exposed examples of classical Midcontinent cyclothems in SE Nebraska (the Virgilian--or uppermost Pennsylvanian--Indian Cave Sandstone). The Core Workshop will feature examples of cyclothemic Carboniferous successions from Illinois, Iowa, Nebraska, Kansas, and Montana, some of which are in active petroleum-producing areas

Geomorphic and Environmental Change Around a Large, Aging Reservoir: Lake C. W. McConaughy, Western Nebraska, USA

Lake C. W. McConaughy, a 63-year-old manmade reservoir in the North Platte Valley of western Nebraska, is the largest standing body of water in the state. From the time that Kingsley Dam was completed in 1941 until the present day (2004), many geomorphic and environmental changes have occurred along the shores and within the North Platte Valley. Erosion on the southeastern shoreline of the lake had been perceived as a problem for landowners and managers for at least three decades, but the full scale of erosion was revealed only after a cumulative 18-m drawdown in lake level: bedrock platforms, extending from cliffs on headlands, as well as minor caves, alcoves, potholes, and beach erosion scarps were revealed. Actual headland retreat since 1941 has probably been on a scale of magnitude of tens of meters. Erosional platforms, however, are as much as 266 m in length, indicating that they are, collectively, the results of a combination of pre-reservoir geomorphic conditions, erosion during reservoir filling, and wave erosion after filling. Serial observations of the shoreline made in the period 1999-2002 demonstrated that shoreline erosion continues. Depositional features such as pocket beaches and beach ridges have formed de novo in bays between headlands. Also, a delta that prograded at least 4 km from the North Platte River into the lake between 1952 and 1993 continues to grow, and major morphometric changes have occurred on the North Platte River immediately upstream since 1941 in response to the elevation of the local base level by the lake; most of the change in channel patterns in the river upstream from the delta took place in a mere 8 years from 1952 to 1960. Since 1999, some emergent beaches and areas of exposed lake floor have developed sand dunes; eolian erosion and re-deposition is widespread elsewhere in these areas during periods of high winds, which are frequent in western Nebraska. The water table beneath lands adjacent to the reservoir generally rose until 1953 as the lake was filling. The far-flung irrigation system of which Lake McConaughy is the key element has elevated water tables as far as 250 km from the lake. Since at least 2000, soil salinization (episodic thenardite accumulation) has developed in exposed lake sediments at the western end of the lake. On a smaller scale, groundwater has been discharging lakeward along shoreline beach scarps through springs and seeps while lake levels have been low. Slightly lowering the operating level of Lake McConaughy could slow some of the more dramatic effects of shoreline erosion when the lake returns to its predrought volume, but erosion will continue, particularly at the ends of headlands on the southeastern shore, which are exposed to strong waves driven by northerly to northwesterly winds. Eolian erosion and re-deposition will, on the other hand, continue as long as lake level remains particularly low as a result of drought and the removal of irrigation waters. Salinization can be considered an ephemeral phenomenon, dependent on future management of the lake, but it indirectly represents the potential for larger-scale changes in hydrogeologic systems. The longer-term effects of lake-related water-table changes, both near the lake and downstream in irrigated lands, as well as the ability of the lake to supply irrigation water if drought conditions continue, remain to be seen

Aquifers of Nebraska II: The Niobrara Aquifer

The marine shale, chalk, marl, and chalky limestone of the Niobrara Formation directly underlie Quaternary sediments in 23 counties from south-central to northeastern Nebraska. Nevertheless, the formation serves as an aquifer only in and around Cedar, Madison, and Nuckolls counties. Niobrara aquifer wells mostly supply irrigation, domestic, and livestock needs. Two hundred of the approximately 230 active registered wells in Nebraska that are screened entirely in the Niobrara aquifer are in Cedar County and environs. About another 200 wells in this area are screened in both the Niobrara aquifer and overlying Quaternary sediments. Wells screened entirely in the Niobrara aquifer in Cedar County range in total depth from about 50 to 220 ft (15 to 67 m) in both confined and unconfined hydraulic conditions. One-fifth of these wells yield 500 gpm (1,900 lpm) or more. Groundwater in the aquifer generally flows north-northeast through Cedar County toward the Missouri River

2021 Nebraska Water Leaders Academy Final Report

Seventeen participants completed the 2021 Water Leaders Academy bringing the total number of graduates to 153 since the inception of the program in 2011. Assessments of participants’ transformational leadership skills, champion of innovation skills, water knowledge, engagement with water issues, civic capacity, entrepreneurial leadership behaviors, and boundary spanner abilities showed significant increases over the course of the year, according to both the participants and their raters. Feedback from the participants was highly positive and constructive. Academy planners are addressing participant concerns. Only minor changes are planned for the 2022 Academy curriculum. Results of the program assessment indicate that the curriculum is meeting Academy objectives. Most importantly, alumni have emerged as leaders in their communities and around the world