The accuracy inherent in the measurement of interproton distances in small molecules by nuclear Overhauser enhancement (NOE) and rotational Overhauser enhancement (ROE) methods is investigated with the rigid model compound strychnine. The results suggest that interproton distances can be established with a remarkable level of accuracy, within a few percent of their true values, using a straight-forward data analysis method if experiments are conducted under conditions that support the initial rate approximation. Dealing with deviations from these conditions and other practical issues regarding these measurements are discussed.

Understanding the potential effects of increased reliance on wastewater treatment plant (WWTP) effluents to meet municipal, agricultural, and environmental flow requires an understanding of the complex chemical loading characteristics of the WWTPs and the assimilative capacity of receiving waters. Stream ecosystem effects are linked to proportions of WWTP effluent under low-flow conditions as well as the nature of the effluent chemical mixtures. This study quantifies the loading of 58 inorganic constituents (nutrients to rare earth elements) from WWTP discharges relative to upstream landscape-based sources. Stream assimilation capacity was evaluated by Lagrangian sampling, using flow velocities determined from tracer experiments to track the same parcel of water as it moved downstream. Boulder Creek, Colorado and Fourmile Creek, Iowa, representing two different geologic and hydrologic landscapes, were sampled under low-flow conditions in the summer and spring. One-half of the constituents had greater loads from the WWTP effluents than the upstream drainages, and once introduced into the streams, dilution was the predominant assimilation mechanism. Only ammonium and bismuth had significant decreases in mass load downstream from the WWTPs during all samplings. The link between hydrology and water chemistry inherent in Lagrangian sampling allows quantitative assessment of chemical fate across different landscapes.

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The U.S. Geological Survey (USGS) is committed to providing the Nation with credible scientific information that helps to enhance and protect the overall quality of life and that facilitates effective management of water, biological, energy, and mineral resources (http://www.usgs.gov/). Information on the Nation's water resources is critical to ensuring long-term availability of water that is safe for drinking and recreation and is suitable for industry, irrigation, and fish and wildlife. Population growth and increasing demands for water make the availability of that water, now measured in terms of quantity and quality, even more essential to the long-term sustainability of our communities and ecosystems. The USGS implemented the National Water-Quality Assessment (NAWQA) Program in 1991 to support national, regional, State, and local information needs and decisions related to water-quality management and policy (http://water.usgs.gov/nawqa). The NAWQA Program is designed to answer: What is the condition of our Nation's streams and ground water? How are conditions changing over time? How do natural features and human activities affect the quality of streams and ground water, and where are those effects most pronounced? By combining information on water chemistry, physical characteristics, stream habitat, and aquatic life, the NAWQA Program aims to provide science-based insights for current and emerging water issues and priorities. From 1991-2001, the NAWQA Program completed interdisciplinary assessments and established a baseline understanding of water-quality conditions in 51 of the Nation's river basins and aquifers, referred to as Study Units (http://water.usgs.gov/nawqa/ studyu.html). In the second decade of the Program (2001-2012), a major focus is on regional assessments of water-quality conditions and trends. These regional assessments are based on major river basins and principal aquifers, which encompass larger regions of the country than the Study Units. Regional assessments extend the findings in the Study Units by filling critical gaps in characterizing the quality of surface water and ground water, and by determining status and trends at sites that have been consistently monitored for more than a decade. In addition, the regional assessments continue to build an understanding of how natural features and human activities affect water quality. Many of the regional assessments employ modeling and other scientific tools, developed on the basis of data collected at individual sites, to help extend knowledge of water quality to unmonitored, yet comparable areas within the regions. The models thereby enhance the value of our existing data and our understanding of the hydrologic system. In addition, the models are useful in evaluating various resource-management scenarios and in predicting how our actions, such as reducing or managing nonpoint and point sources of contamination, land conversion, and altering flow and (or) pumping regimes, are likely to affect water conditions within a region. Other activitie...

the SWSI forecasted water demand and USGS compilation estimates may be due to increased conservation efforts, which were not included in the water-demand forecasts, and the differing methodology in deriving the forecasted and estimated values. A generalized comparison of the published 1985 estimates to water withdrawal estimates 20 years later in 2005 can provide some indication of State water-use trends. Estimates of total water withdrawals were compared for the categories of total irrigation (crop and golf course) public supply (including population), self-supplied domestic (including population), self-supplied industrial, livestock, mining, and thermoelectric. Commercial water use was estimated in 1985 but was not compiled in 2005. Total withdrawals for the seven categories compiled in 1985 and 2005 did not differ greatly and indicated an increase of less than 1 percent. A number of water-use categories indicated an increase in water withdrawals in the 20 years from 1985 to 2005, which included public supply, self-supplied domestic, self-supplied industrial, and thermoelectric uses. These water-use categories can be directly linked to population increases and reflect the overall State population growth from 3.2 million in 1985 to 4.7 million in 2005. As a consequence of increased population and the need for more electricity and manufactured and processed goods, water withdrawals for thermoelectric generation increased 12.2 percent and self-supplied industrial increased 18.4 percent between 1985 and 2005. A number of water-use categories decreased between 1985 and 2005, including irrigation, livestock, and mining. Irrigation estimates decreased the least during these 20 years, less than 1 percent; however, irrigated acres decreased by approximately 10 percent. Livestock withdrawals decreased 45.6 percent and mining decreased 76.5 percent. The decrease in mining withdrawals reflects the decrease in the number of active coal and hard-rock mines in Colorado from 150 in 1985, to 20 in 2005. Water Withdrawals by Category Water withdrawal information for 2005 was compiled for seven categories: irrigation (crop and golf course), public supply, self-supplied domestic, self-supplied industrial, livestock, mining, and thermoelectric. For each category, surfacewater and groundwater withdrawal volumes were compiled and are shown as totals for the State by county (table 2, fig. 4) and by four-digit HUC (table 3). Water withdrawals by category are presented for the hydrologic subregions (hydrologic unit code) in tables 1-1 to 1-9 in the appendix. A summary of instream water use for hydroelectric power generation also was compiled. Public supply Water withdrawn by public and private water suppliers and delivered to users. Public suppliers provide water for a variety of uses, such as domestic, commercial, industrial, thermoelectric power (domestic and cooling purposes), and public-water use. Also see domestic water use, commercial water use, industrial water use, public-water use, and other water use. Public supply deliveries ...