bluuebunny/crossref_metadata_2025 huggingface dataset:
IN‐SITU CONSOLIDATION OF LAKE DEPOSITS: AN EMPIRICAL MODEL TO RECONSTRUCT POLLUTION HISTORY1
Authors: Vink Jos P. M. , Winkels Herman J.
Published: June 2007

ABSTRACT: In the past, much effort has been put into the development of sophisticated mathematical models to describe settlement and consolidation of water deposited sediments. Such models often aim at completeness and accuracy in modeling the physical processes involved. However, as a result of the generality of the descriptions, the models often fail to compute local circumstances satisfactorily. In specific cases, the empirical approach may prove to be highly competitive and reliable. In large water bodies in the central part of the The Netherlands, the alluvial “IJsselmeer‐deposit” is a common type of fresh water sediment. Its deposition and settlement started in 1932, when anthropogenic activities changed the physical and chemical conditions of the lakes drastically. Five representative cores of this sediment were taken in deep zones of the lakes. Periodic water depth surveys over the last sixty years at these locations provided information on the net sedimentation rate and the total thickness of this Ijsselmeer‐deposit at known time intervals. In order to calculate a time‐equivalent of the depth scale, correction factors for soil consolidation are introduced. A decrease in the total thickness of individual sediment layers is proportional to the decrease of its volume, which is derived from in situ characteristics. Correction factors are based on a simplification of various stages of compression (i.e., O percent, 30 percent, and 45 percent). A factor n, which represents changes of water content of the sediment as a dependence of clay content, is derived for each layer, allowing an inverse calculation procedure to determine the initial, uncompressed thickness of each layer. Hence, a fairly reliable time scale in depth can be reconstructed. Furthermore, the radionuclide activity was measured in some cores and the degree of organic and inorganic pollution was determined in numerous layers of all cores. Cs‐isotopic tracers (137Cs, 134Cs) give a good reconstruction of the last six decades of physical changes of the sediment and the degree of pollution, assuming post depositional redistribution and transformation of pollutants to be negligible. The results showed close coherence to calculated time‐scales.
PREDICTING TEMPORAL AND SPATIAL FLOOD DYNAMICS USING A PRECALIBRATED MODEL1
Authors: Huston Michael A. , Fontaine Thomas A.
Published: June 2007

ABSTRACT: A large storm in December 1990 allowed the evaluation of flood predictions from a hydrologic model (TOPMODEL) that had been previously calibrated on the West Fork of Walker Branch Watershed, a gauged 37.5 ha catchment near Oak Ridge, Tennessee. The model predicts both hydrograph dynamics and the spatial distribution of overland flow using an index based on topography. Maximum extent of overland flow during the storm was determined from patterns of leaf litter removal from valley bottoms. Both the flood hydrograph and the extent of overland flow were accurately predicted using model parameters obtained from a three‐month period of normal flow conditions during 1983.
IMPACTS OF AGRICULTURAL DRAINAGE WELL CLOSURE ON CROP PRODUCTION: A WATERSHED CASE STUDY1
Authors: Mohanty B. P. , Tim U. S. , Anderson C. E. , Woestman T.
Published: June 2007

ABSTRACT: Much of north‐central Iowa is characterized by flat topography, shallow depressions, and poor natural surface drainage. Land drainage systems comprising of tile drains and agricultural drainage wells (ADWs) are used as outlets for subsurface drainage of cropland under corn and soybean production. Studies have shown that these drainage systems, mainly the ADWs, are potential routes for agricultural chemicals to underground aquifers. To protect the region's vital groundwater resource, researchers are evaluating alternative outlets ranging from complete closure of existing ADWs (and creation of wetlands) to continued use of ADWs and chemical management in a comprehensive policy framework.

This paper presents the results of a study designed to provide government jurisdictions, farmers, and land managers information for assessing the impact of closing ADWs on crop production. The study couples a geographic information systems database for a 471‐hectare watershed in Humboldt County, Iowa, with a groundwater flow model (MODFLOW) and an empirical crop yield loss model to predict long‐term effects of complete closure of ADWs on crop production. The cropland areas inundated and the relative crop yield loss due to ADW closure are determined as a function of long‐term climatic data. The results indicate that elimination of drainage outlets in the watershed could result in ponding of low‐lying areas and poorly drained soils, making them unsuitable for crop production. Such wetness also decreases the efficiency of production in the no‐ponding areas by isolating fields, and the crop yield loss can be reduced by an annual average of about 18 percent.
PRECIPITATION DISTRIBUTION IN COASTAL BRITISH COLUMBIA1
Authors: Loukas Athanasios , Quick Michael C.
Published: June 2007

ABSTRACT: The spatial distribution and the temporal and spatial variation of the annual, seasonal, and monthly precipitation in two mountainous watersheds in southwestern British Columbia, Canada, have been analyzed using a detailed database for 1971–1990 in the Capilano and Seymour watersheds. The analysis showed that the precipitation increases up to the mid‐position of the watersheds, and then either levels off or decreases. Precipitation on mountain slopes and in the valley at the same distance from the beginning of the slope is similar, and the barrier height is identified as the dominant parameter which influences the precipitation distribution. The temporal variation of the precipitation is the smallest at the mid‐position of the watersheds. This variability is the least in the fall and winter and largest in the summer. Correlation between the precipitation accumulations at various stations is large, ranging from 0.80 for the wet period of October‐March to 0.65 for the dry period of April‐September for distances less than 32 km. Comparison with other studies and the analyses of precipitation and runoff data from coastal British Columbia showed that the results of this study are perhaps general and thus transferable to similar areas in the coastal Pacific Northwest.
MERCURY CONTAMINATION AND FLOODPLAIN SEDIMENTATION FROM FORMER GOLD MINES IN NORTH GEORGIA1
Authors: Leigh David S.
Published: June 2007

ABSTRACT: Gold was discovered in Georgia in 1829 and mined until about 1940 in the Dahionega Gold Belt of the north Goorgia Piedmont. Streams there are characterized by gravel beds and fine sandy to silty banks. Historical mining‐related alluvium is clearly distinguished from prehistoric alluvium because it is contaminated with mercury (Hg), which was used by miners to amalgamate gold. Mercury concentrations in historical floodplain sediments range from 0.04 to 4.0 mg kg−1, exceeding background (0.04 mg kg1) by as much as two orders of magnitude near the core of the mining district and decreasing in the downstream direction. Low levels (≤ 0.1 mg kg1) of Hg are established within about 10–15 km from the source mines. The mercury‐contaminated sediment exceeds sediment quality guidelines set by many agencies, and is a significant nonpoint source for mercury pollution. Hydraulic mining of saprolite, which began in 1868, and cutting of forests associated with mining and settlement caused unusually rapid sedimentation (1–3 cm yr−l) and floodplain aggradation in the region. After mining ceased, streams adjusted by downcutting and forming an historical‐age terrace. A new floodplain is currently being formed as streams migrate lateraily and erode the mining‐related sediment of the historical terrace. High magnitude floods are contained within the confines of the historical terrace, thus limiting quantities of over‐bank sedimentation, causing channel bank erosion, and transmitting high sediment yields to reservoirs in the region.
CLEAN WATER ACT REAUTHORIZATION: HOW FAR HAVE WE COME?1
Authors: Freeman A. Myrick.
Published: June 2007

ABSTRACT: This paper first presents a brief review of an earlier effort to estimate the benefits associated with achieving the Clean Water Act objectives. It then discusses what would be involved in doing a retrospective benefit‐cost analysis of the Clean Water Act and some information on changes in several measures of water quality over the past 20 years. The paper concludes with a summary of a recent effort to estimate the realized benefits associated with the Clean Water Act and some implications for policy. (KEY TERMS: benefits; benefit‐cost analysis; costs; recreation; water pollution; water quality.)
ATRAZINE IN SPRING RUNOFF AS RELATED TO ENVIRONMENTAL SETTING EBRASKA, 19921
Authors: Stamer John K , Swanson Robert B. , Jordan Paul R.
Published: June 2007

ABSTRACT: A synoptic sampling of five surface‐water sites in central Nebraska was conducted by the U.S. Geological Survey as part of its National Water‐Quality Assessment Program during storm runoff in May 1992 to relate transport, yields, and concentrations of atrazine to environmental setting. Atrazine was the most extensively applied pesticide in the study unit. Atrazine transport was related to the size of contributing drainage area, quantity of atrazine applied, amount of precipitation, and volume of stream‐flow. Estimated yields and mean concentrations of atrazine were related to the percentage of cropland in a drainage area. The largest estimated yields and mean concentrations of atrazine in surface water were associated from drainage areas with the highest percentage of cropland, and the smallest was associated with the smallest amount of cropland. Atrazine concentrations increased as streamflow increased but decreased at or near the time of peak streamflows, perhaps due to dilution. Atrazine concentrations then increased and remained elevated far into the stream recession. Atrazine is a regulated contaminant in finished public‐water supplies. Large concentrations of atrazine could affect the management of public‐water supplies because atrazine remains in solution in contrast to many other pesticides that are more easily removed.
THE SENSITWITY OF NORTHERN SIERRA NEVADA STREAMFLOW TO CLIMATE CHANGE1
Authors: Duell Lowell F W.
Published: June 2007

ABSTRACT: The sensitivity of streamflow to climate change was investigated in the American, Carson, and Truckee River Basins, California and Nevada. Nine gaging stations were used to represent streamflow in the basins. Annual models were developed by regressing 1961–1991 streamflow data on temperature and precipitation. Climate‐change scenarios were used as inputs to the models to determine streamflow sensitivities. Climate‐change scenarios were generated from historical time series by modifying mean temperatures by a range of +4°C to—4°C and total precipitation by a range of +25 percent to ‐25 percent. Results show that streamflow on the warmer, lower west side of the Sierra Nevada generally is more sensitive to temperature and precipitation changes than is streamflow on the colder, higher east side. A 2°C rise in temperature and a 25‐percent decrease in precipitation results in stream‐flow decreases of 56 percent on the American River and 25 percent on the Carson River. A 2°C decline in temperature and a 25‐percent increase in precipitation results in streamflow increases of 102 percent on the American River and 22 percent on the Carson River.
STATISTICAL CHARACTERISTICS OF COAL‐MINE DISCHARGES ON WESTERN PENNSYLVANIA REMINING SITES1
Authors: Hawkins Jay W.
Published: June 2007

ABSTRACT: Under an approved remining program, a coal mine operator can remine abandoned sites without legally assuming treatment responsibilities of the previously degraded water, as long as these discharging waters are not further degraded. Determination of discharge degradation caused by remining of abandoned coal mines requires knowledge of mine water quality and discharge flow rate characteristics both before and after remining. Normality tests performed on the water quality and flow data from 57 mine discharges indicate generally nonnormal distributions and extreme right‐skewness. Exploratory data analysis (notched box‐and‐whisker plots) of the differences among medians indicates that the water quality of underground mines was more highly degraded in terms of acidity, iron, and sulfate concentrations than that from surface mines. Spearman's rank correlation tests, normality testing, and exploratory data analysis indicate that discharge flow rate is the primary controlling factor on the variability of pollution load rate. Reduction of recharge from the surface and adjacent unmined strata should decrease the mine discharge flow rate and in turn the pollution load.
THE EFFECTWENESS OF PRICING AS A STAND‐ALONE WATER CONSERVATION PROGRAM1
Authors: Jordan Jeffrey L.
Published: June 2007

ABSTRACT: Economic theory clearly indicates that the use of increasing rate structures will reduce the demand for water and produce monetary incentives for consumers to conserve. One problem with estimating the effectiveness of using rate structures as a conservation program is that they are usually accompanied by other conservation efforts. Thus, it is difficult to determine the effectiveness of any one conservation component. This paper examines the effectiveness of increasing rate structures in a situation where no other conservation program was introduced. The paper uses customer data from the Spalding County (Georgia) Water Authority where an increasing rate structure replaced a descending rate structure in January 1991. Since the imposition of the increasing rate structure, the number of customers has increased 21 percent while total water demand has gone up only 15 percent and per customer water use has declined 5 percent. The daily water use per connection has declined from 243 gallons in 1990 to 231 in 1993, and monthly use has gone from 7,381 gallons to 7,028 per connection over the same period. Statistical tests indicate that water consumption during the two periods was significantly different while weather factors were not.
PARAMETER DETERMINATION FOR THE MUSKINGUM‐CUNGE FLOOD ROUTING METHOD1
Authors: Bravo Rolando , Dow David A. , Rogers Jerry R.
Published: June 2007

ABSTRACT: The proportionality coefficient, K, and the weighing parameter, X, required for the Muskingum‐Cunge Flood Routing Method are dependent on the hydraulic characteristics of the channel and the dynamic characteristic of the flood wave. This work focuses on the determination of the Muskingum‐Cunge Flood Routing Method parameters for streams where measured hydrographs are not available (i.e., ungaged streams) with floods that stay within the channel banks. In the present work, a gaged creek was used and a dynamic wave was routed to test the reliability of the parameters determined through the Schaefer and Stevens technique (Schaefer and Stevens, 1978). The predicted outflow hydrographs are compared to the hydrographs obtained for the same stream determined with the Muskingum Routing option of the HEC‐1 program. Cypress Creek in Harris County, Texas, was the model for this work; and the corresponding data were extracted from the Grant Road and Westfield, Texas, USGS gaging stations.
COMBINED SEWER OVERFLOW CONTROL THROUGH IN‐RECEWING WATER STORAGE: AN EFFICIENCY EVALUATION1
Authors: Field Richard , Pitt Robert , Jager Debra , Brown Michael
Published: June 2007

ABSTRACT: A demonstration and efficiency evaluation project was conducted for the flow balancing method (FBM) facility, a combined sewer overflow (CSO) storage facility at Fresh Creek in Brooklyn, New York City. The FBM is a curtained tank located directly in the receiving water that captures CSO. The CSO floats on top of and displaces Fresh Creek saltwater before it is pumped back to the publicly owned treatment works (POTW). The facility was a pilot scale subject to the full CSOs. The purpose of the project was to show how the FBM can withstand severe weather and tidal conditions and to develop a procedure for estimating CSO control efficiency (percentage of CSO pumped back to the POTW). The procedure proved successful and incorporated specific conductivity as a tracer in mass balance equations. These equations provided estimates of the net percent, capture‐pumpback of the CSO using the FBM, including the amount of Fresh Creek water that was included in the pumpback to the P01W. The efficiency was directly related to the volume of the CSO and the pumpback rate and ranged from a low of 3.3 percent for the largest event to a high of 76.9 percent for the smallest event. Recent FBM enlargement should result in substantial increases in CSO control. The FBM facility has operated successfully for over five years, withstanding ice storms, near hurricane force winds and up to 7 ft tidal range.
WATER MARKETING: THE CASE OF INDIAN RESERVED RIGHTS1
Authors: McNally Mary
Published: June 2007

ABSTRACT: Water marketing is an increasing important topic for policy makers and water managers, especially in the Western United States. Indian reserved rights (or Winters rights) differ in significant ways from water rights under most state prior appropriation systems. As Winters rights are quantified, a number of issues are emerging concerning the extent to which these water rights may be marketed, particularly to off‐reservation users. This paper will review the evolution of Indian reserved water rights and discuss key issues surrounding the marketing of these rights.
SIZING SMALL STORMWATER PUMP STATIONS1
Authors: Froehlich David C.
Published: June 2007

ABSTRACT: Design of a stormwater pump station is a complicated procedure because of the large number of parameters that are involved. Even the most basic pump station serving a small catchment requires a computationally intensive iterative evaluation. However, the design problem consists primarily of finding the combination of temporary storage and pump capacity that accommodates runoff of the selected recurrence interval for the least cost. A procedure is developed for rapidly obtaining the needed relation between storage volume and discharge for small pump stations where a constant outflow can be assumed and the inflow hydro‐graph can be represented using the modified rational method with rainfall given by a widely‐used intensity‐duration equation. Accepting the limitations of the modified rational method and the simplifications applied to pump station operation, the procedure provides an uncomplicated way of rapidly finding the stormwater runoff volume that needs to be temporarily stored for given values of pump discharge and activation water level (or, equivalently, activation storage volume). Ultimate determination of temporary runoff storage will depend on an economic analysis of the trade‐off between storage volume and pump capacity.
CONFLICTING PERSPECTWES ABOUT DETECTION LIMITS AND ABOUT THE CENSORING OF ENVIRONMENTAL DATA1
Authors: Clark Malcolm J. R. , Whitfield Paul H.
Published: June 2007

ABSTRACT: Current conventions for reporting analytical results from environmental samples brings the objectives of laboratory scientists into conflict with those of environmental scientists. The objective of chemical analyses is to provide estimates of the true composition of samples. Reported results must reflect the analytical uncertainty. Current conventions require left‐censoring of those results below the Limit of Detection. The objective of statistical interpretation of environmental data is to provide estimates of the characteristics of ecosystems. Such statistical analyses are often confounded by left‐censoring of analytical results. We review the different points of view and propose a compromise which recognizes these conflicting perspectives.
POTENTIAL FOR REDUCING NITROGEN POLLUTION THROUGH IMPROVED AGRONOMIC PRACTICES1
Authors: Trachtenberg Eric , Ogg Clayton
Published: June 2007

ABSTRACT: According to the 1990 National Water Quality Inventory nutrient runoff from agriculture is one of the largest contributors to watershed contamination. Nutrient balance studies suggest that many farmers use more fertilizer than necessary because of insufficient crediting for nutrients coming from manure and legumes. Using data from the USDA's 1990 Farm Costs and Returns Survey, we found that farmers raising only conventional crops spend between $470 to $624 million more per year on fertilizer than necessary. This accounts for a range of 24 percent to 32 percent of total annual nitrogen (N) purchases. The excess N amounts to between 2.5 to 3.3 billion pounds N and has considerable water pollution potential. Farmers and the fertilizer industry have responded positively to highly focused research and education programs which support improved crediting of these nutrients.
SALINITY INCREASES IN THE NAVAJO AQUIFER IN SOUTHEASTERN UTAH1
Authors: Naftz David L. , Spangler Lawrence E.
Published: June 2007

ABSTRACT: Salinity increases in water in some parts of the Nava‐jo aquifer in southeastern Utah have been documented previously. The purpose of this paper is to use bromide, iodide, and chloride concentrations and del oxygen‐18 and deuterium values in water from the study area to determine if oil‐field brines (OFB) could be the source of increased salinity. Mixing‐model results indicate that the bromide‐to‐chloride X 10,000 weight ratio characteristic of OFB in and outside the study area could not be causing the bromide depletion with increasing salinity in the Navajo aquifer. Mixing‐model results indicate that a mixture of one percent OFB with 99 percent Navajo aquifer water would more than double the bromide‐to‐chloride weight ratio, instead of the observed decrease in the weight ratio with increasing chloride concentration. The trend of the mixing line representing the isotopically enriched samples from the Navajo aquifer does not indicate OFB as the source of isotopically enriched water; however, the simulated isotopic composition of injection water could be a salinity source. The lighter isotopic composition of OFB samples from the Aneth, Ratherford, White Mesa Unit, and McElmo Creek injection sites relative to the lsmay site is a result of continued recycling of injection water mixed with various proportions of isotopically lighter make‐up water from the alluvial aquifer along the San Juan River. A mixing model using the isotopic composition of the simulated injection water suggests that enriched samples from the Navajo aquifer are composed of 36 to 75 percent of the simulated injection water. However, chloride concentrations predicted by the isotopic mixing model are up to 13.4 times larger than the measured chloride concentrations in isotopically enriched samples from the Navajo aquifer, indicating that injection water is not the source of increased salinity. Geochemical data consistently show that OFB and associated injection water from the Greater Aneth Oil Field are not the source of salinity increases in the Navajo aquifer.
ESTIMATING DRAINAGE AREA ON STEEP UNIFORM SLOPES1
Authors: Abt Steven R. , Thornton Christopher I. , Johnson Terry L.
Published: June 2007

ABSTRACT: A study was conducted to derive a simple procedure for estimating the tributary drainage area that may potentially develop at the base of a uniformly graded, steep slope. Data were extracted from a nil development flume study in which 112 rills and their tributary drainage areas were documented. The tributary drainage area for each rill was correlated to the slope length and the slope gradient. The findings are considered applicable to planar, convex, and divergent slopes with lengths of up to 130 m. Field verification is needed to extend the applicability of the relation.
CAUSES OF PEAK FLOWS IN NORTHWESTERN MONTANA AND NORTHEASTERN IDAHO1
Authors: MacDonald Lee H. , Hoffman James A.
Published: June 2007

ABSTRACT:Both catchment experiments and a review of hydrologic processes suggest a varying effect of forest harvest on the magnitude of peak flows according to the cause of those peak flows. In northwestern Montana and Northeastern Idaho, annual maximum flows can result from spring snowmelt, rain, mid‐winter rain‐on‐snow, or rain‐on‐spring‐snowmelt. Meteorologic and physical data were used to determine the cause of annual maximum flows in six basins which had the necessary data and were smaller than 150 mi2. Rain‐on‐spring‐snowmelt was the most frequent cause of annual maximum flows in all six basins, although there was a strong gradient in the magnitude and cause of peak flows from southwest to northeast. Less frequent mid‐winter rain‐on‐snow events caused the largest flows on record in four basins. Mid‐winter rain‐on‐snow should be distinguished from rain‐on‐spring‐snowmelt because of differences in seasonal timing, the relative contributions of rain vs. snowmelt, and the projected effects of forest harvest. The effects of mixed flood populations on the flood‐frequency curve varied from basin to basin. Annual maximum daily flows could not be reliably predicted from rainfall and snowmelt data.
MODEL DEVELOPMENT FOR CONJUNCTIVE USE STUDY OF THE SAN JACINTO BASIN, CALIFORNIA1
Authors: Wang Chuching , Mortazavi Behrooz , Liang Wen‐Kang , Sun Ne‐Zheng , Yeh William W‐G.
Published: June 2007

ABSTRACT: A two‐layered confined‐unconfined numerical model for flow and mass transport is developed for the San Jacinto Basin. The model structure is determined by the geological structure of the Basin and model parameters are calibrated using 20 years of historical records. The total number of historical head observations used for the flow model calibration is 1,117 and the total number of the estimated parameters is 91. The two‐layered transport model is also calibrated using historical water quality records. Sensitivity analysis of the flow model shows that only 68 parameters (out of a total of 91) are relatively sensitive and reliable. However, the unreliable parameters (23 of them) are found to be insensitive and thus not significant to the prediction and management of conjunctive use of surface water and ground water. The developed flow model has been used to study the two proposed artificial recharge scenarios for the San Jacinto Basin. We have found that during a relatively dry condition, an artificial recharge rate of 80 acre‐ft/day can be achieved during the recharge period October through January. However, for a relatively wet condition, only 80 percent of the proposed rate can be effectively stored in the Basin during these months.
MEASURED AND PREDICTED VELOCITY AND LONGITUDINAL DISPERSION AT STEAI)Y AND UNSTEADY FLOW, COLORADO RIVER, GLEN CANYON DAM TO LAKE MEAD1
Authors: Graf Julia Badal
Published: June 2007

ABSTRACT: The effect of unsteadiness of dam releases on velocity and longitudinal dispersion of flow was evaluated by injecting a fluorescent dye into the Colorado River below Glen Canyon Dam and sampling for dye concentration at selected sites downstream. Measurements of a 26‐kilometer reach of Glen Canyon, just below Glen Canyon Dam, were made at nearly steady dam releases of 139, 425, and 651 cubic meters per second. Measurements of a 380‐kilometer reach of Grand Canyon were made at steady releases of 425 cubic meters per second and at unsteady releases with a daily mean of about 425 cubic meters per second. In Glen Canyon, average flow velocity through the study reach increased directly with discharge, but dispersion was greatest at the lowest of the three flows measured. In Grand Canyon, average flow velocity varied slightly from subreach to subreach at both steady and unsteady flow but was not significantly different at steady and unsteady flow over the entire study reach. Also, longitudinal dispersion was not significantly different during steady and unsteady flow. Long tails on the time‐concentration curves at a site, characteristic of most rivers but not predicted by the one‐dimensional theory, were not found in this study. Absence of tails on the curves shows that, at the measured flows, the eddies that are characteristic of the Grand Canyon reach do not trap water for a significant length of time. Data from the measurements were used to calibrate a one‐dimensional flow model and a solute‐transport model. The combined set of calibrated flow and solute‐transport models was then used to predict velocity and dispersion at potential dam‐release patterns.
CONTROL OF SUSPENDED SOLIDS AND PHYTOPLANKTON WITH FISHES AND A MUSSEL1
Authors: Heifrich Louis A. , Zimmerman Mark , Weigmann Diana L.
Published: June 2007

ABSTRACT: Filtering efficiency of the fathead minnow (Pimephales promelas), gizzard shad (Dorosoma cepedianum), carp (Cyprinus carpio), and a freshwater mussel (Elliptio coinpianata) was measured in field and laboratory trials to assess the ability of each species to control phytoplankton and suspended solid densities. All fish species tested were ineffective filterers and generally increased, rather than suppressed, algal and suspended solid concentrations. Filtering efficiencies of fish varied between ‐354 and 84 percent, depending on the size, shape, abundance, palatability, composition, and resistance to digestion of the particles. Because of poor filtering abilities, unpredictable feeding habits, and sensitivity to stress, the fish species examined are not effective biological controls in waste lagoons. In contrast, the freshwater mussel Elliptio was a highly effective control organism, averaging 66 percent filtering efficiency over a wide size range of algal and suspended particles. Filtration efficiency was positively correlated with mussel density. Elliptio was efficient at filtering small particles, which are particularly difficult to remove. Mean filtration rates ranged from 53 to 134 ml/mussel/h depending on the algal species consumed and algal densities (range 50–180,000 cells/ml) and 3 mg/L/mussel/h on suspended solids (range 14 to 112 mg/L). Water clarification was facilitated by both direct consumption and pseudofeces deposition. Elliptio and probably other mussel species can effectively control algae and suspended solids in wastewater lagoons and eutrophic lakes, if environmental conditions, especially dissolved oxygen levels, are suitable (>5 mg/L) for their survival.
DEVELOPING AND IMPLEMENTING DECISION SUPPORT SYSTEMS: A CRITIQUE AND A CHALLENGE1
Authors: Loucks Daniel P.
Published: June 2007

ABSTRACT: Computer‐based models together with their interactive interfaces are typically called decision support systems. DSSs are interactive computer‐based information providers. The common objective of all DSSs, regardless of the frameworks, methodologies, or techniques used, is to provide timely information that supports human decision makers ‐ at whatever level of decision making. The informational needs of the decision making process are the key considerations that motivate the development of DSSs. The growth of DSS development and use has been substantial. In spite of this impressive growth, computer‐aided decision support systems can still be improved and made more useful to those they are intended to support. Researchers and practitioners, and indeed the computer industry, continue to identify ways of doing this. This paper reviews some of these needs and opportunities by focusing on the process of successful DDS development and implementation. The paper outlines an approach and some guidelines for developing DSSs. The approach emphasizes and requires considerable interaction between the DSS developers (analysts) and the DSS users (decision makers). This interaction and feedback is required throughout the entire DSS building, testing and evaluation (debugging), and implementation processes. The paper concludes by identifying some research needs and opportunities affecting DSS development and effective use.
ASSESSMENT OF GULLY‐CONTROL STRUCTURES IN THE RIO NUTRIA WATERSHED, ZUNI RESERVATION, NEW MEXICO1
Authors: Gellis Allen C. , Cheama Andres , Laahty Vanissa , Lalio Sheldon
Published: June 2007

ABSTRACT: During the latter part of the 19th century and the early part of the 20th century, a major cycle of erosion, arroyo cutting, and gullying occurred in the southwestern United States. Since this erosion cycle began, many projects to control erosion, such as the Civilian Conservation Corps projects in the 1930s, were initiated. However, in the Southwestern United States few studies have documented the effect of these structures in reducing erosion or their effect on gully systems. As part of a watershed rehabilitation project on the Zuni Reservation, New Mexico, 47 structures made either of earth or rocks and 23 rock and brush structures were assessed. Sixty percent of the 47 earth or rock structures have breached and relative to dam height, 65 percent of 47 structures are more than 50 percent silted. Of the 23 rock and brush structures, 22 percent have breached or are close to breaching. Reasons for breaching of all structural types may be piping, scour immediately below the structures, large runoff and large drainage area, poor maintenance, headcutting, and active arroyo deepening and widening. In most cases, documentation does not exist on structure design, the specific purpose for a structure, or when these structures were built.
COPING WITH A SEVERE SUSTAINED DROUGHT ON THE COLORADO RWER: INTRODUCTION AND OVERVIEW1
Authors: Young Robert A.
Published: June 2007

ABSTRACT: In arid regions of rapid economic and population growth, adverse effects of droughts are likely to be increasingly serious. This article presents an introduction and overview of the papers collected in this special issue of the Water Resources Bulletin. The papers report on the second phase of a study of the impacts of and responses to a potential severe sustained drought in the Colorado River Basin in the southwestern U.S. The analyses were performed by a consortium of researchers from universities and the private sector located throughout the Basin. Tree ring studies suggest that droughts of duration and magnitude much more serious than any found in the modern records probably occurred in the Basin during earlier centuries. Taking the present‐day configuration of the storage and diversion structures and the economic conditions in the Basin as the base‐point, the general objectives of the study are three: first, to define a representative Severe Sustained Drought (SSD) and assess its hydrologic impacts; second, to forecast the economic, social and environmental impacts on the southwestern U.S.; and finally, to assess alternative institutional arrangements for coping with an SSD. The evaluation of impacts and policies was conducted with two distinct modeling approaches. One involved hydrologic‐economic optimization modeling where water allocation institutions are decision variables. The second was a simulation‐gaming approach which allowed “players” representing each basin state to interact in a real‐time decision making mode in response to the unfolding drought.
INSTITUTIONAL OPTIONS FOR THE COLORADO RIVER1
Authors: Kenney Douglas S.
Published: June 2007

ABSTRACT: In many interstate river basins, the institutional arrangements for the governance and management of the shared water resource are not adequately designed to effectively address the many political, legal, social, and economic issues that arise when the demands on the resource exceed the available supplies. Even under normal hydrologic conditions, this problem is frequently seen in the Colorado River Basin. During severe sustained drought, it is likely that the deficiencies of the existing arrangements would present a formidable barrier to an effective drought response, interfering with efforts to quickly and efficiently conserve and reallocate available supplies to support a variety of critical needs. In the United States, several types of regional arrangements are seen for the administration of interstate water resources. These arrangements include compact commissions, interstate councils, basin interagency committees, interagency‐interstate commissions, federal‐interstate compact commissions, federal regional agencies, and the single federal administrator. Of these options, the federal‐interstate compact commission is the most appropriate arrangement for correcting the current deficiencies of the Colorado River institution, under all hydrologic conditions.
A GAMING EVALUATION OF COLORADO RWER DROUGHT MANAGEMENT INSTITUTIONAL OPTIONS1
Authors: Henderson James L. , Lord William B.
Published: June 2007

ABSTRACT: Researchers representing each of the Colorado River Basin states as well as the Secretary of the Interior were presented with an interactive computer simulation of a progressively increasing drought and were given the collective opportunity to change the ways in which basin‐wide and within‐state water management were conducted. The purpose of this “gaming” exercise was to identify rules for managing the Colorado River which are effective in preventing drought‐caused damages to basin water users. This water management game was conducted three times, varying the collective choice roles for management of the river yet staying substantially within the current institution for management of the Colorado River known as the “Law of the River.” The Law of the River was quite effective in minimizing drought impacts upon consumptive water uses. Additional effective drought‐coping measures to protect consumptive uses consisted mostly of intrastate water management improvements which states were able to implement independently. The Law of the River did not protect non‐consumptive water uses, such as hydroelectric power generation, water‐based recreation, endangered species, and water quality from drought, as well as it protected consumptive water uses. Players reached collective choice decisions to cope with rising salinity, equalize storage between the upper and lower basins, and protect endangered species. While these measures had some success, only reductions in withdrawals for consumptive uses, particularly in the upper basin, could have substantially lessened adverse impacts.
RURAL NONPOINT SOURCE POLLUTION CONTROL IN WISCONSIN: THE LIMITS OF A VOLUNTARY PROGRAM?1
Authors: Wolf Aaron T.
Published: June 2007

ABSTRACT: This paper examines the relationship between best‐management practices, institutional needs, and improved water quality within the watersheds of Wisconsin's program for controlling rural nonpoint source pollution. The first section describes the federal requirements for state nonpoint source programs and the legislative and management methods the state of Wisconsin uses to put those requirements into practice. The emphasis of the paper, described in the second section, is the institutional difficulty in evaluating the success of a large, integrated water quality program. Measurements which are investigated include (1) watershed water quality before and after implementation of BMPs; (2) program participation as measured by eligible vs. participating landowners, BMPs considered necessary vs. BMPs implemented, or dollars allocated to the NPS program vs. dollars expended; and (3) institutional goal coordination and management effectiveness. It is found that, despite the size and sophistication of Wisconsin's NPS program, there is little if any improvement in ambient water quality in these watersheds, probably because of a general lack of adequate participation in this voluntary program.
FLOW DURATION CURVES II: A REVIEW OF APPLICATIONS IN WATER RESOURCES PLANNING1
Authors: Vogel Richard M. , Fennessey Neil M.
Published: June 2007

ABSTRACT: A streamflow duration curve illustrates the relationship between the frequency and magnitude of streamflow. Flow duration curves have a long history in the field of water‐resource engineering and have been used to solve problems in water‐quality management, hydropower, instream flow methodologies, water‐use planning, flood control, and river and reservoir sedimentation, and for scientific comparisons of streamflow characteristics across watersheds. This paper reviews traditional applications and provides extensions to some new applications, including water allocation, wasteload allocation, river and wetland inundation mapping, and the economic selection of a water‐resource project.
UNCERTAINTY ANALYSIS OF BMP EFFECTWENESS FOR CONTROLLING NITROGEN FROM URBAN NONPOINT SOURCES1
Authors: Griffin Carol B.
Published: June 2007

ABSTRACT: The effectiveness of urban Best Management Practices (BMPs) in achieving the No‐Net‐Increase Policy (NNTP), a policy designed to limit nonpoint nitrogen loading to Long Island Sound (US), is analyzed. A unit loading model is used to simulate annual nitrogen exported from the Norwalk River watershed (Connecticut) under current and future conditions. A probabilistic uncertainty analysis is used to incorporate uncertainty in nitrogen export coefficients and BMP nitrogen removal effectiveness. The inclusion of uncertainty in BMP effectiveness and nitrogen export coefficients implies that additional BMPs, or BMPs with a greater effectiveness in nitrogen removal, will be required to achieve the NNIP. Even though including uncertainty leads to an increase in BMP implementation rates or BMP effectiveness, this type of analysis provides the decision maker with a more realistic assessment of the likelihood that implementing BMPs as a management strategy will be successful. Monte Carlo simulation results indicate that applying BMPs to new urban developments alone will not be sufficient to achieve the NNIP since BMPs are not 100 percent effective in removing the increase in nitrogen caused by urbanization. BMPs must also be applied to selected existing urban areas. BMPs with a nitrogen removal effectiveness of 40–60 percent, probably the highest level of removal that can be expected over an entire watershed, must be applied to at least 75 percent of the existing urban area to achieve the NNIP This high rate of application is not likely to be achieved in urbanized watersheds in the LIS watershed; therefore, additional point source control will be necessary to achieve the NNIP
SEASONAL PUMPING VARIATION EFFECTS ON WELLHEAD PROTECTION AREA DELINEATION1
Authors: Ramanarayanan Tharacad S. , Storm Daniel E. , Smolen Michael D.
Published: June 2007

ABSTRACT: Delineation of a welihead protection area (WHPA) is the key element in welihead protection programs for drinking water supplies. WHPAs are often delineated under idealized conditions using simple steady‐state assumptions, which lead to an incorrect estimation of area and geometry. In this paper, we compare the results from a simple steady‐state procedure commonly employed in WHPA delineation with a more complex transient approach that allows consideration of seasonal variation in pumping rates. We also introduce a transient procedure to delineate time‐related capture zones using a numerical ground water flow and transport model. Welihead delineation is examined for two municipal wells in Tipton, Oklahoma, using a ten‐year time‐of‐travel criterion. In the steady‐state procedure, where we assumed constant pumping rates, we used GPTRAC, a semi‐analytical model, and MOC, a numerical model. The capture zone delineated by GPTRAC is comparable in shape with the capture zone delineated by MOC but not in size due to the differences in solution schemes. In the transient procedure, we used MOC and considered the seasonal variation in pumping rates. The capture zones delineated in this procedure were larger than the capture zones delineated by the steady‐state procedure using the same model. Further analysis showed that a higher drawdown was predicted in the transient procedure than in the steady‐state procedure, which is the reason for larger capture zones.
CONTROL OF STREAMBANK EROSION DUE TO BED DEGRADATION WITH VEGETATION AND STRUCTURE1
Authors: Shields F. D. , Bowie A. J. , Cooper C. M.
Published: June 2007

ABSTRACT: Combinations of vegetation and structure were applied to control streambank erosion along incised stream channels in northwest Mississippi. Eleven sites along seven channels with contributing drainage areas ranging from 12–300 km2 were used for testing. Tested configurations included eroding banks protected by vegetation alone, vegetation with structural toe protection, vegetation planted on re‐graded banks, and vegetation planted on regraded banks with toe protection. Monitoring continued for up to 10 years, and casual observation for up to 18 years. Sixteen woody and 13 nonwoody species were tested. Native woody species, particularly willow, appear to be best adapted to stream‐bank environments. Sericea lespedeza and Alamo switchgrass were the best nonwoody species tested. Vegetation succeeded in reaches where the bed was not degrading, competition from kudzu was absent, and bank slopes were stabilized by grading or toe protection. Natural vegetation invaded planted and unplanted stable banks composed of fertile soils. Designs involving riprap toe protection in the form of a longitudinal dike and woody vegetation appeared to be most cost‐effective. The exotic vine kudzu presents perhaps the greatest long‐term obstacle to restoring stable, functional riparian zones along incised channels in our region. (KEY TERMS: vegetation; streambank protection; bioengineering; stream restoration; channel incision; riparian zone.)
RASTER‐BASED HYDROLOGIC MODELING OF SPATIALLY‐VARIED SURFACE RUNOFF1
Authors: Julien Pierre Y. , Saghafian Bahram , Ogden Fred L.
Published: June 2007

ABSTRACT: The proliferation of watershed databases in raster Geographic Information System (GIS) format and the availability of radar‐estimated rainfall data foster rapid developments in raster‐based surface runoff simulations. The two‐dimensional physically‐based rainfall‐runoff model CASC2D simulates spatially‐varied surface runoff while fully utilizing raster GIS and radar‐rainfall data. The model uses the Green and Ampt infiltration method, and the diffusive wave formulation for overland and channel flow routing enables overbank flow storage and routing. CASC2D offers unique color capabilities to display the spatio‐temporal variability of rainfall, cumulative infiltrated depth, and surface water depth as thunderstorms unfold. The model has been calibrated and independently verified to provide accurate simulations of catchment response to moving rainstorms on watersheds with spatially‐varied infiltration. The model can accurately simulate surface runoff from flashfloods caused by intense thunderstorms moving across partial areas of a watershed.
MODELING GROUND WATER FLOW USING FLUX BOUNDARY CONDITIONS1
Authors: Bravo Rolando , Rogers Jerry R. , Cleveland Theodore G.
Published: June 2007

ABSTRACT: Determination of the boundary conditions for modeling ground water flow is a critical point especially in regional models. Normally the regional models require model areas that are greater than the given area of interest. This work focuses on the prediction of hydraulic heads in regional models using flux boundary conditions. The model uses flux boundary conditions that were estimated using a radial flow analog and Darcy's law. The regional model that is presented uses no parameter identification (inverse estimation) procedures. In the present work, the Houston area was used. The simulation of the hydrological conditions of the Chicot and Evangeline Aquifers that underlie the Houston area were made using the available information about the geological profile in the Houston region and the current information about the existing production wells. The regional model works as a forward problem. The system parameters such as hydraulic conductivity, specific storage, and hydrological stresses were specified, and the model predicts the hydraulic head. Actual data from piezometers operated by the U.S. Geological Survey (USGS) in many places throughout Houston were used as initial conditions. Some piezometric head data were generated using the regional variable theory called kriging to supply head estimates in areas where data were unavailable. The Modular Three Dimensional Finite Difference Groundwater Flow Model developed by the USGS was used to predict the hydraulic heads. The predicted ground water heads are compared to the actual data. The results show that the model performs well for locations where data were available.