Fresh Water Studies Commons^™

Use Of Long Term Weather Data And Spatially Delineated Field Attributes To Predict Water And Energy Conservation From Variable Rate Irrigation, Sahil Sharma

Department of Biological Systems Engineering: Dissertations and Theses

The declining levels of the Ogallala aquifer calls for more judicious use of water. Studies have shown that VRI has the potential for water savings. But adoption of VRI is still very low. The major reason is lack of information on the returns from the VRI systems and its feasibility in different fields. Also, a quantification of the required reduction in prices of VRI is necessary. So, an economic return analysis of VRI strategies was done to compare it to uniform irrigation management (UIM) using a water balance model based on long term weather data and field properties for a …

Suitability Of River Delta Sediment As Proppant, Missouri And Niobrara Rivers, Nebraska And South Dakota, 2015, Ronald B. Zelt, Christopher M. Hobza, Bethany L. Burton, Nathaniel J. Schaepe, Nadine M. Piatak-Hackley

United States Geological Survey: Water Reports and Publications

Document abstract

Sediment management is a challenge faced by reservoir managers who have several potential options, including dredging, for mitigation of storage capacity lost to sedimentation. As sediment is removed from reservoir storage, potential use of the sediment for socioeconomic or ecological benefit could potentially defray some costs of its removal. Rivers that transport a sandy sediment load will deposit the sand load along a reservoir-headwaters reach where the current of the river slackens progressively as its bed approaches and then descends below the reservoir water level. Given a rare combination of factors, a reservoir deposit of alluvial sand has …

Micro-Spi Sediment Profile Imaging Micro-Inspector, Andrew P. Corvin, Caleb T. Davies, Matt R. Ferrari

Mechanical Engineering

This project was proposed by Dr. Brian Paavo through a desire to more easily study the benthic sediment layers of the ocean. To do so, he asked us to build a simple and compact machine for use in sediment profile imagery (SPI). Although devices like this already exist, they are all large scale devices that require a ship with a crane to deploy, which is expensive and time consuming. Instead, he desired a “micro” SPI, which is capable of being deployed from a small vessel that can easily navigate shallow waters. Our interpretation of these requirements was as follows: a …

Understanding N-Nitrosodimethylamine Formation In Water: Chloramine Chemistry, Kinetics, And A Proposed Reaction Pathway, Huong Thu Pham

Graduate Theses and Dissertations

The formation of N-nitrosodimethylamine (NDMA) in drinking water systems is a concern because of its potential carcinogenicity and occurrence at toxicologically relevant levels. The postulated mechanism for NDMA formation involves a substitution between dichloramine and amine-based precursors to form an unsymmetrical dimethylhydrazine (UDMH), which is then oxidized by ground-state molecular oxygen to form NDMA. However, this latter reaction is spin forbidden, thus likely occurs at a slow rate. It is hypothesized that the reaction between monochloramine and hydroxylamine (a nitrification product) may form an intermediate, which is involved in the NDMA formation pathway. This intermediate may also be generated from …

Oxidation Of Substituted Catechols At The Air-Water Interface: Production Of Carboxylic Acids, Quinones, And Polyphenols, Elizabeth A. Pillar, Marcelo I. Guzman

Chemistry Faculty Publications

Anthropogenic activities contribute benzene, toluene, and anisole to the environment, which in the atmosphere are converted into the respective phenols, cresols, and methoxyphenols by fast gas-phase reaction with hydroxyl radicals (HO(•)). Further processing of the latter species by HO(•) decreases their vapor pressure as a second hydroxyl group is incorporated to accelerate their oxidative aging at interfaces and in aqueous particles. This work shows how catechol, pyrogallol, 3-methylcatechol, 4-methylcatechol, and 3-methoxycatechol (all proxies for oxygenated aromatics derived from benzene, toluene, and anisole) react at the air-water interface with increasing O3(g) during τc ≈ 1 μs contact time and contrasts their …

Compensatory Response Of Fathead Minnow Larvae Following A Pulsed In-Situ Exposure To A Seasonal Agricultural Runoff Event, Jonathan M. Ali, John Sangster, Daniel D. Snow, Shannon L. Bartelt-Hunt, Alan S. Kolok

Nebraska Water Center: Faculty Publications

Agriculturally-dominated waterways such as those found throughout the Midwestern United States often experience seasonal pulses of agrichemical contaminants which pose a potential hazard to aquatic organisms at varying life stages. The objective of this study was to characterize the developmental plasticity of fathead minnow larvae in a natural environment subject to a seasonal episodic perturbation in the form of a complex mixture of agricultural stressors. Fathead minnow larvae were maintained at the Elkhorn River Research Station for a 28-d in situ exposure to an agrichemical pulse event.Minnow larvae were sampled after 14 and 28 days to characterize developmental plasticity through …

Spatiotemporal Distribution Of Eutrophication In Lake Tai As Affected By Wind, Wenhui Zhang, Qiujin Xu, Xixi Wang, Xiaozhen Hu, Cheng Wang, Yan Pang, Yanbin Hu, Yang Zhao, Xiao Zhao

Civil & Environmental Engineering Faculty Publications

One common hypothesis is that wind can affect concentrations of nutrients (i.e., nitrogen and phosphorus) and chlorophyll-a (Chl-a) in shallow lakes. However, the tests of this hypothesis have yet to be conclusive in existing literature. The objective of this study was to use long-term data to examine how wind direction and wind speed affect the spatiotemporal variations of total nitrogen (TN), total phosphorus (TP) and Chl-a in Lake Tai, a typical shallow lake located in east China. The results indicated that the concentrations of nutrients and Chl-a tended to decrease from the northwest to the southeast of Lake Tai, with …

Water–Soil–Vegetation Dynamic Interactions In Changing Climate, Xixi Wang, Xuefeng Chu, Tingxi Liu, Xiangju Cheng, Rich Whittecar

Civil & Environmental Engineering Faculty Publications

Previous studies of land degradation, topsoil erosion, and hydrologic alteration typically focus on these subjects individually, missing important interrelationships among these important aspects of the Earth's system. However, an understanding of water–soil–vegetation dynamic interactions is needed to develop practical and effective solutions to sustain the globe's eco-environment and grassland agriculture, which depends on grasses, legumes, and other fodder or soil-building crops. This special issue is intended to be a platform for a discussion of the relevant scientific findings based on experimental and/or modeling studies. Its 12 peer-reviewed articles present data, novel analysis/modeling approaches, and convincing results of water–soil–vegetation interactions under …