A Mathmatical model of primary productivity and limnological patterns in Lake Mead

The temporal and spatial changes in chemical and biological properties of Lake Mead have been investigated, thereby indicating the sources of water pollution and the time of highest pollution potential. Planktonic organisms have been shown to indicate the presence of water problems. Macro- and micro-nutrient analyses have shown that primary productivity is not inhibited by limiting concentrations. A mathematical model has been developed, tested with one set of independent data, and shown worthy of management utility. Although the model works very well for the Lake Mead area, the physical reality of the Multiple Linear Regression equation should be tested on independent data

Phytoplankton distribution and water quality indices for Lake Mead (Colorado River)

Phytoplankton samples were collected in Lake Mend 6 times from September 1910 to June 1971 for 8 stations at depths of 0. 3, 5, 10, 20, and 30 m. These samples were processed through a Millipore filter apparatus and 79 planktonic algae were identified. Algal divisions represented were Bacillariophyta, 42 species; Chlorophyta, 18 ; Cyanophyta, 9; Chrysophyta, 3; Cryptophyta, 3; Pyrrophyta, 2; and Euglenophyta, 2. Blue-green algae were dominant in late summer and fall; green algae, diatoms, and, cryptomonads in winter; and green algae in spring. The early summer flora was best represented by the Chlorophyta, Cryptophyta, and Chrysophyta. Palmer\u27s pollution-tolerant algae indices and Nygaard\u27s indices were calculated from phytoplankton data. These indices suggest eutropic conditions in Lake Mead, especially for Boulder Basin

Review of GroundWater Quality Monitoring Network Design

Ground-water quality monitoring network design is defined as the selection of sampling sites and (temporal) sampling frequency to determine physical, chemical, and biological properties of ground water. The main approaches to ground-water quality monitoring network design were identified as hydrogeologic and statistical. The various methods for network design available in the hydrologic literature have been evaluated by considering the spatial scale of the monitoring program, the objective of sampling, data requirements, temporal effects, and range of applicability. Considerable advance has been made over the last two decades that now permit the application of methodical and testable approaches to ground-water quality monitoring network design, although they mostly serve for preliminary analysis and design. The opinion of the Task Committee on Ground-Water Quality Monitoring Network Design is that as there continues to be advances in hydrogeochemistry, ground-water hydrology, and risk and geostatistical analysis, methods for ground-water quality monitoring network design will be improved and refined, and they will become ever more useful in the important mission of environmental protection. © ASCE

Micronutrients and biological patterns in Lake Mead

Progressive increases in concentration of dissolved solids in the Colorado River water from Lake Powell to Imperial Dam seem to alter plankton dynamics and biological productivity of the river. Also, changes in biological productivity and micronutrients concentrations occur within the same reservoir. Development of a digital simulation model to predict micronutrients concentrations and biological productivity is necessary for diagnosing changes in plankton population and effluent-carrying capacity of the system. The objectives of the study are: (1) to determine trace metal balance at different locations in Lake Mead, (2) to measure biological productivity and conduct plankton population counts at each sampling location, (3) to derive functions relating biological productivity to trace metal concentrations, suspended sediments and some physical variables (temperature, light, solar radiation), and (4) to develop a mathematical model for predicting spatial and temporal changes in biological productivity, plankton dynamics and trace elements concentrations. Data acquisition is limited to the identification of the principal parameters which relate to the biology and chemical properties of the aquatic system(s). The data is subjected to mathematical analysis to identify trends in spatial and temporal planktonic variabilities. Extensive chemical and hydrodynamic studies have been attempted on Lake Mead. The United States Geological Survey publishes annually an extensive report containing water chemistry at Hoover Dam and Bright Angel Creek. Additional chemical data are collected by the Bureau of Reclamation and is reported in the following publication series: CHE-46 (1965), CHE-70 (1970), REC-ERC-71-11 (1971). The Environmental Protection Agency (FWQA) has completed minor investigations on Lake Mead in their report of January 1967 and of October 1968. These studies were performed in the light of the monumentous efforts of Anderson and Pritchard (1951) and Smith et al. (1954). Hill (1965) draws a note of caution by his prediction of the quality of Colorado River water. Outside of the limited work by the EPA and Moffett (1943), hydrobiology has been neglected. This report constitutes the first integrated scheme of chemistry, hydrobiology and hydrodynamics. The original direction was to follow assumptions derived through our first zooplankton and chemical analyses of Lake Mead. At that time we felt that the chemistry data would indicate a sharp drop in primary productivity (PPR) from South Cove to Hoover Dam. Our zooplankton data, however, indicated that Boulder Basin was experiencing stress either chemically or biologically. The early chemistry study indicated the lack of certain required micronutrients across the system. We are satisfied that the PPR does drop from South Cove to Bonelli Landing; however, we did not expect the accelerated eutrophication covering the whole of Boulder Basin

Concerns over use of glyphosate-based herbicides and risks associated with exposures: a consensus statement

Abstract The broad-spectrum herbicide glyphosate (common trade name "Roundup") was first sold to farmers in 1974. Since the late 1970s, the volume of glyphosate-based herbicides (GBHs) applied has increased approximately 100-fold. Further increases in the volume applied are likely due to more and higher rates of application in response to the widespread emergence of glyphosate-resistant weeds and new, pre-harvest, dessicant use patterns. GBHs were developed to replace or reduce reliance on herbicides causing well-documented problems associated with drift and crop damage, slipping efficacy, and human health risks. Initial industry toxicity testing suggested that GBHs posed relatively low risks to non-target species, including mammals, leading regulatory authorities worldwide to set high acceptable exposure limits. To accommodate changes in GBH use patterns associated with genetically engineered, herbicide-tolerant crops, regulators have dramatically increased tolerance levels in maize, oilseed (soybeans and canola), and alfalfa crops and related livestock feeds. Animal and epidemiology studies published in the last decade, however, point to the need for a fresh look at glyphosate toxicity. Furthermore, the World Health Organization's International Agency for Research on Cancer recently concluded that glyphosate is "probably carcinogenic to humans." In response to changing GBH use patterns and advances in scientific understanding of their potential hazards, we have produced a Statement of Concern drawing on emerging science relevant to the safety of GBHs. Our Statement of Concern considers current published literature describing GBH uses, mechanisms of action, toxicity in laboratory animals, and epidemiological studies. It also examines the derivation of current human safety standards. We conclude that: (1) GBHs are the most heavily applied herbicide in the world and usage continues to rise; (2) Worldwide, GBHs often contaminate drinking water sources, precipitation, and air, especially in agricultural regions; (3) The half-life of glyphosate in water and soil is longer than previously recognized; (4) Glyphosate and its metabolites are widely present in the global soybean supply; (5) Human exposures to GBHs are rising; (6) Glyphosate is now authoritatively classified as a probable human carcinogen; (7) Regulatory estimates of tolerable daily intakes for glyphosate in the United States and European Union are based on outdated science. We offer a series of recommendations related to the need for new investments in epidemiological studies, biomonitoring, and toxicology studies that draw on the principles of endocrinology to determine whether the effects of GBHs are due to endocrine disrupting activities. We suggest that common commercial formulations of GBHs should be prioritized for inclusion in government-led toxicology testing programs such as the U.S. National (Continued on next page

A mathematical model of primary productivity and limnological patterns in Lake Mead

The temporal and spatial changes in chemical and biological properties of Lake Mead have been investigated, thereby indicating the sources of water pollution and the time of highest pollution potential. Planktonic organisms have been shown to indicate the presence of water problems. Macro- and micro-nutrient analyses have shown that primary productivity is not inhibited by limiting concentrations. A mathematical model has been developed, tested with one set of independent data, and shown worthy of management utility. Although the model works very well for the Lake Mead area, the physical reality of the MLR equation should be tested on independent data.hydrology collectio

Constraints and Categories of Vadose Zone Monitoring Devices

UA affiliates can use the link in "Additional Links" to access this article.Traditional monitoring methods using chemical analysis of ground water samples to detect pollutant migration are being superseded or used in conjunction with innovative approaches. A need to detect pollutants before they reach the water table has drawn interest to vadose (unsaturated) zone monitoring and brought together hydrogeologists, soil scientists and agricultural engineers who have been working on this subject for years. Recent studies have identified over 50 different types of vadose zone monitoring devices and methods that have optimum utility in varying hydrogeologic settings. In general, measurements made in the vadose zone are trying to define storage, transmission of liquid waste in terms of flux and velocity, and pollutant mobility. Criteria for the selection of alternative vadose zone monitoring methods are important for the development of site-specific systems. These criteria include: type of site; applicability to new, active, and abandoned sites; power requirements; depth limitations; multiple use capability; type of data collection system; reliability and life expectancy; degree of operational complexity; direct versus indirect methods; applicability to alternate media; effect on flow regime; and effect of hazardous waste on sampling or measurements. Application of the selection criteria is discussed in Everett et al. (1982a).This item is part of the Water Resources Research Center collection. It was digitized from a physical copy provided by the Water Resources Research Center at The University of Arizona. For more information about items in this collection, please contact the Center, (520) 621-9591 or see http://wrrc.arizona.edu