bluuebunny/crossref_metadata_2025 huggingface dataset:
DENSITY CURRENT INTRUSIONS IN AN ICE‐COVERED URBAN LAKE1
Authors: Ellis Christopher R. , Champlin Jerry , Stefan Heinz G.
Published: June 2007

ABSTRACT: Evidence is presented that snowmelt runoff from an urban watershed can produce density current intrusions (underflows) in a lake. Several episodes of density current intrusions are documented. Water temperatures and salinities measured near the bottom of a 10 m deep Minneapolis lake during the late winter warming periods in 1989, 1990, 1991, and 1995 show significant rapid changes which are correlated with observed higher air temperatures and snowmelt runoff. The snowmelt runoff entering this particular lake (Ryan Lake) has increased electrical conductivity, salinity, and density. The source of the salinity is the salt spread on urban streets in the winter. Heating of littoral waters in spring may also contribute to the occurrence of the sinking flows, but is clearly not the only cause.
A LOW COST DRIP IRRIGATION SYSTEM FOR SMALL FARMERS IN DEVELOPING COUNTRIES1
Authors: Polak Paul , Nanes Bob , Adhikari Deepak
Published: June 2007

ABSTRACT: In areas where water is scarce, drip irrigation provides the most efficient way to conserve irrigation water, but its cost of £1000 an acre is prohibitive for most small farmers in developing countries. The cost was reduced by 90 percent by (1) making dripper lines moveable, so that each line reaches ten rows instead of one; (2) replacing 25‐cent emitters with simple 0.70 mm holes punched by a heated needle; and (3) using £3.00 off‐the‐shelf 20 liter containers with cloth filters in place of expensive filter systems. This reduced the cost of a half‐acre system to £50. The low cost system was field tested in the hill areas of Nepal, and in mulberry cultivation in Andhra Pradesh, India. Uniformity of flow from emitters was 73–84 percent. Small farmers reported that the low cost trickle irrigation system cut labor requirements in half, and doubled the area irrigated by the same amount of water. The low cost drip system is likely to be widely adopted by small farmers in semi‐arid and hilly regions.
COST MINIMIZATION OF NUTRIENT REDUCTION IN WATERSHED MANAGEMENT USING LINEAR PROGRAMMING1
Authors: Schleich Joachim , White David
Published: June 2007

ABSTRACT: Linear programming is applied to identify the least cost strategy for reaching politically specified phosphorus and total suspended solids reduction targets for the Fox‐Wolf river basin in Northeast Wisconsin. The programming model uses data collected on annualized unit reduction costs associated with five categories of sources of phosphorus and total suspended solids discharge in each of the 41 sub‐watersheds in the basin to determine the least cost management strategy. Results indicate that: (1) cost‐effective nutrient reduction requires careful selection of geographic areas and source categories to address throughout the watershed; (2) agricultural sources are the most cost‐effective to address in the basin; and (3) care should be exercised in setting nutrient reduction targets, given that there are likely to be significantly increasing marginal costs of nutrient reduction; the model predicts that lowering the most restrictive target by 33 percent would cut reduction expenditures by about 75 percent. Policy implications of the model include support for the investigation and potential development of institutional arrangements that enable cost‐effective nutrient reduction activities to occur, such as the creation of an agency with authority over a given watershed, coordinated watershed management activities, or nutrient trading programs.
KNOWLEDGE UTILIZATION IN WATER MANAGEMENT IN THE NETHERLANDS RELATED TO DESICCATION1
Authors: Boogerd Annelie , Groenewegen Peter , Hisschemöller Matthijs
Published: June 2007

ABSTRACT: The use of scientific knowledge in environmental policy making is an important topic. However, the relation between knowledge producers and policy makers is not a straightforward producer‐user relationship. The development of a national desiccation policy in the Netherlands and the implementation of desiccation plans in local situations are used as a case study to investigate the knowledge policy relationship. Three theoretical explanations were used to analyze this case: a difference between the cultures of producers and users; a different rationality of the policy making and research processes; and processes of social construction of problem definitions which imply that different knowledge stocks are used depending on the framing of the policy problem. Emergence of the policy issue at the national level is demonstrated to develop in close interaction between knowledge producers and policy makers, while the interactions at the local level were more based on integration of expert knowledge through personal expertise and closely tied to the development of management plans. This case study thus reveals a difference between general knowledge supporting measures at the national policy level and the way in which specific knowledge is applied in local cases. Therefore more attention should be paid to the translation of policy problems from rather high levels of political authority to the conceptualization at lower management levels. A final conclusion is that knowledge use in Dutch desiccation policy can be understood by pointing to multiple theoretical perspectives. The rational actor model and a construc‐tivist perspective turned out to be especially useful in explaining the different ways knowledge was used at the national and the local level.
STREAM WATER CHEMISTRY IN WATERSHEDS RECEIVING DIFFERENT ATMOSPHERIC INPUTS OF H+, NH4, NO3−, AND SO42−1
Authors: Stottlemyer Robert
Published: June 2007

ABSTRACT: Weekly precipitation and stream water samples were collected from small watersheds in Denali National Park, Alaska, the Fraser Experimental Forest, Colorado, Isle Royale National Park, Michigan, and the Calumet watershed on the south shore of Lake Superior, Michigan. The objective was to determine if stream water chemistry at the mouth and upstream stations reflected precipitation chemistry across a range of atmospheric inputs of H+, NH4+, NO3−−, and SO42−. Volume‐weighted precipitation H+, NH4+, NO3−−, and SO42− concentrations varied 4 to 8 fold with concentrations highest at Calumet and lowest in Denali. Stream water chemistry varied among sites, but did not reflect precipitation chemistry. The Denali watershed, Rock Creek, had the lowest precipitation NO3−− and SO42− concentrations, but the highest stream water NO3−and SO42− concentrations. Among sites, the ratio of mean monthly upstream NO3−− concentration to precipitation NO3−‐ concentration declined (p < 0.001, R2= 0.47) as precipitation NO3−− concentration increased. The ratio of mean monthly upstream to precipitation SO42− concentration showed no significant relationship to change in precipitation SO42− concentration. Watersheds showed strong retention of inorganic N (> 90 percent inputs) across inputs ranging from 0.12 to > 6 kg N ha−1 y−1. Factors possibly accounting for the weak or non‐existent signal between stream water and precipitation ion concentrations include rapid modification of meltwater and precipitation chemistry by soil processes, and the presence of unfrozen soils which permits winter mineralization and nitrification to occur.
STREAM MEANDER RESTORATION1
Authors: Rinaldi Massimo , Johnson Peggy A.
Published: June 2007

ABSTRACT: Stream meander restoration designs currently used by many state and local government agencies are often based on empirical equations, such as those developed by Leopold and Wolman (1957; 1960). In order to assess the suitability of these equations and propose alternative strategies, 18 sites in Central Maryland were selected and data on channel planform, cross‐sections, sediments, and spacing and sizing of the pools and riffles were collected and analyzed to characterize the channel type in the study area. A large bias was found comparing the meander parameters measured to those computed using the Leopold and Wolman equations for the streams in central Maryland. Based on these results, appropriate empirical equations for the study area that can assist in stream restoration designs were investigated. An additional approach that can assist in stream restoration consists of the application of a detailed stream reconnaissance to verify that the restoration project is consistent with the natural form and processes of the river.
IN‐STREAM HABITAT UNIT CLASSIFICATION: INADEQUACIES FOR MONITORING AND SOME CONSEQUENCES FOR MANAGEMENT1
Authors: Poole Geoffrey C. , Frissell Christopher A. , Ralph Stephen C.
Published: June 2007

ABSTRACT:Habitat unit classification can be a useful descriptive tool in hierarchical stream classification. However, a critical evaluation reveals that it is applied inappropriately when used to quantify aquatic habitat or channel morphology in an attempt to monitor the response of individual streams to human activities. First, due to the subjectivity of the measure, observer bias seriously compromises repeatability, precision, and transferability of the method. Second, important geomorphic and ecological changes in stream habitats are not always manifested as changes in habitat‐unit frequency or characteristics. Third, classification data are nominal, which can intrinsically limit their amenability to statistical analysis. Finally, using the frequency of specific habitat unit types (e.g., pool/riffle ratio or percent pool) as a response variable for stream monitoring commonly leads to the establishment of management thresholds or targets for habitat‐unit types. This, in turn, encourages managers to focus on direct manipulation or replacement of habitat structures while neglecting long‐term maintenance or re‐establishment of habitat‐forming biophysical processes. Stream habitat managers and scientists should only use habitat unit classification to descriptively stratify in‐stream conditions. They should not use habitat unit classification as a means of quantifying and monitoring aquatic habitat and channel morphology. Monitoring must instead focus on direct, repeatable, cost‐efficient, and quantitative measures of selected physical, chemical, and biological components and processes spanning several scales of resolution.
STATE ACTIONS TO MITIGATE DROUGHT LESSONS LEARNED1
Authors: Wilhite Donald A.
Published: June 2007

ABSTRACT: Drought has been a common feature in the United States during the past decade and has resulted in significant economic, social, and environmental impacts in virtually all parts of the nation. The purpose of this paper is two fold. First, the status of state drought planning is discussed to illustrate the significant increase in the number of states that have prepared response plans ‐ from three states in 1982 to 27 in 1997. In addition, six states are now in various stages of plan development. Second, mitigative actions implemented by states in response to the series of severe drought years since 1986 are summarized. This information was obtained through a survey of states. The study concludes that states have made significant progress in addressing drought‐related issues and concerns through the planning process. However, existing plans are still largely reactive in nature, treating drought in an emergency response mode. Mitigative actions adopted by states provide a unique archive that may be transferable to other states. Incorporating these actions into a more anticipatory, risk management approach to drought management will help states move away from the traditional crisis management approach.
ALTERED STREAMFLOW AND SEDIMENT ENTRAINMENT IN THE GUNNISON GORGE1
Authors: Elliott J. G. , Parker R. S.
Published: June 2007

ABSTRACT: The Gunnison River in the Gunnison Gorge is a canyon river where upstream dams regulate mainstem discharge but do not affect debris‐flow sediment supply from tributaries entering below the reservoirs. Regulation since 1966 has altered flood frequency, streambed mobility, and fluvial geomorphology creating potential resource‐management issues. The duration of moderate streamflows between 32.3 and 85.0 m3/s has increased threefold since 1966. This, along with flood‐peak attenuation, has facilitated fine‐sediment deposition and vegetation encroachment on stream banks. The Shields equation and on‐site channel geometry and bed‐material measurements were used to assess changes in sediment entrainment in four alluvial reaches. Sand and fine gravel are transported through riffle/pool reaches at most discharges, but the cobbles and boulders composing the streambed in many reaches now are infrequently entrained. Periodic debris flows add coarse sediment to rapids and can increase pool elevation and the streambed area affected by backwater and fine‐sediment accumulation. Debris‐flow supplied boulders accumulate on fans and in rapids and constrict the channel until reworked by larger floods. The response to streamflow‐régime changes in the Gunnison Gorge could serve as an analog for alluvial reaches in other regulated canyon rivers.
EVALUATION OF CURVE NUMBER PROCEDURES TO PREDICT RUNOFF IN GLEAMS1
Authors: Shirmohammadi Adel , Yoon Kwang S. , Rawls Walter J. , Smith Oliver H.
Published: June 2007

ABSTRACT: Proper selection of curve number values will improve the capability of the SCS‐Curve Number procedure in predicting runoff. Both CREAMS and GLEAMS models use the Smith and Williams (1980) approach of converting CNII (curve number value for average antecedent moisture conditions) into CNI (curve number value for dry antecedent moisture conditions) in calculating the soil retention parameter (S). CREAMS and GLEAMS have been found to under predict runoff because of the internal conversion of CNII to CNI. This study shows modifications of the GLEAMS model using CMI without converting it to CM and it also shows the seasonal curve number approaches with and without converting CNII to CNI. Results indicate that using CNII without internal conversion to CNI provides better runoff and erosion predictions than the original version of GLEAMS and versions with seasonal curve numbers when tested with four years of field data in the Coastal Plain physiographic region of Maryland.
COMPARISON OF 1‐D AND 2‐D MODELING OF OVERLAND RUNOFF AND SEDIMENT TRANSPORT1
Authors: Hong Seonggu , Mostaghimi Saied
Published: June 2007

ABSTRACT: One‐dimensional and two‐dimensional modeling approaches were compared for their abilities in predicting overland runoff and sediment transport. Both 1‐D and 2‐D models were developed to test the hypothesis that the 2‐D modeling approach could improve the model predictions over the 1‐P approach, based on the same mathematical representations of physical processes for runoff and sediment transport. The models developed in this study were applied to overland areas with cross slopes. A hypothetical case and an experimental study reported by Storm (1991) were used. Based on the simulation results from the selected hypothetical case and experimental study, the 2‐D model provided better representation of spatial distribution of flow depths and sediment concentrations than the 1‐D model. However, no significant differences in predictions of total runoff volume and sediment yield at the outlet area were found between the 1‐D and 2‐D models.
HYDROLOGIC CALIBRATION OF THE SWAT MODEL IN A WATERSHED CONTAINING FRAGIPAN SOILS1
Authors: Peterson J. R. , Hamlett J. M.
Published: June 2007

ABSTRACT: The Soil and Water Assessment Tool (SWAT) model, designed for use on rural ungaged basins and incorporating a GRASS GIS interface, was used to model the hydrologic response of the Ariel Creek watershed of northeastern Pennsylvania. Model evaluation of daily flow prior to calibration revealed a deviation of runoff volumes (Dv) of 68.3 percent and a Nash‐Sutcliffe coefficient of‐0.03. Model performance was affected by unusually large observed snowmelt events and the inability of the model to accurately simulate baseflow, which was influenced by the presence of fragipans. Seventy‐five percent of the soils in the watershed contain fragipans. Model calibration yielded a Dv of 39.9 percent and a Nash‐Sutcliffe coefficient of 0.04, when compared on a daily basis. Monthly comparisons yielded a Nash‐Sutcliffe coefficient of 0.14. Snowmelt events in the springs of 1993 and 1994, which were unusually severe, were not adequately simulated. Neglecting these severe events, which produced the largest and third largest measured flows for the period of record, a Dv of 4.1 percent and Nash‐Sutcliffe coefficient of 0.20 were calculated on a daily comparison, while on a monthly basis the Nash‐Sutciffe coefficient was 0.55. These results suggest that the SWAT model is better suited to longer period simulations of hydrologic yields. Baseflow volumes were accurately simulated after calibration (Dv= ‐0.2 percent). Refinements made to the algorithms controlling subsurface hydrology and snowmelt, to better represent the presence of fragipans and snowmelt events, would likely improve model performance.
ASSESSMENT OF HYDRAULIC PROPERTIES IN AN UNCONFINED ALLUVIAL AQUIFER NEAR GRAND ISLAND, NEBRASKA1
Authors: Chen Xunhong
Published: June 2007

ABSTRACT: A method is presented to analyze time‐drawdown data from one or more observation wells for the calculation of four hydraulic parameters for unconfined aquifers: vertical hydraulic conductivity, horizontal hydraulic conductivity, storage coefficient, and specific yield. The hydraulic parameter results are further analyzed for reliability and the possible ranges of the actual parameter values. After verification using a theoretical example, the method was used to analyze pumping test data from 22 observation wells in an unconfined alluvial aquifer near Grand Island, Nebraska. Results indicate that this method can be used to efficiently calculate the four hydraulic parameters in this type of aquifer. The method can also identify the impact of measurement errors on the parameter estimates, and provide ranges of the actual parameter values. The parameter values calculated using this method were compared to those determined using other theories. It is found that this method is very useful for calculating the hydraulic properties from pumping test data and for analyzing the parameter reliability.
EVALUATION OF PROBABILITY DENSITY FUNCTIONS IN PRECIPITATION MODELS FOR THE PACIFIC NORTHWEST1
Authors: Duan Jinfan , Selker John , Grant Gordon E.
Published: June 2007

ABSTRACT:Recent work has found that a one‐parameter Weibull model of wet day precipitation amount based on the Weibull distribution provides a better fit to historical daily precipitation data for eastern U.S. sites than other one‐parameter models. The general two‐parameter Weibull distribution was compared in this study to other widely used distributions for describing the distribution of daily precipitation event sizes at 99 sites from the U.S. Pacific Northwest. Surprisingly little performance was sacrificed by reducing the two‐parameter Weibull to a single‐parameter distribution. Advantages of the single‐parameter model included requiring only the mean wet day precipitation amount for calibration, invertibility for simulation purposes, and ease of analytical manipulation. The fit of the single‐parameter Weibull to the 99 stations included in this study was significantly better than other single‐parameter models tested, and performed as well as the widely endorsed, more cumbersome, two‐parameter gamma model. Both the one‐and two‐parameter Weibull distributions are shown to have b‐moments that are consistent with historical precipitation data, while the ratio of b‐skew and b‐variance in the gamma model is inconsistent with the historical recerd by this measure. In addition, it was found that the two‐parameter gamma distribution was better fit using the method of moments estimators than maximum likelihood estimates. These findings suggested that the distribution in precipitation among sites in the Pacific Northwest with dramatically different settings are nearly identical if expressed in proportion to the mean site event size.
LAND USE AND STREAMWATER NITRATE‐N DYNAMICS IN AN URBAN‐RURAL FRINGE WATERSHED1
Authors: Wernick B. G. , Cook K E. , Schreier H.
Published: June 2007

ABSTRACT: Agricultural and residential activities are key non‐point sources of nitrogen pollution in urban‐rural fringe areas. A GIS‐based watershed approach was used to compare land use indicators (septic system and animal unit densities), to streamwater nitrate‐N in the Salmon River near Vancouver, B.C., Canada. The density of septic systems was used as an indicator of residential development while animal unit density was used as an indicator of the intensity of agricultural activity. Nitrate‐nitrogen (nitrate‐N) concentrations as high as 7.1 mg·L−1 were found in the mid‐portion of the watershed during the summer months, when streamflow is low and groundwater comprises a large proportion of water in the stream. The major aquifer supplying water to the midsection of the watershed is contaminated with nitrate‐N. A comparison of the relationships between septic system and animal unit density and nitrate‐N in the upstream to downstream direction provided evidence that both residential and agricultural activities contribute to elevated nitrate‐N in the Salmon River mainstem. In contrast, only septic system density corresponded to the pattern of streamwater nitrate‐N in Coghlan Creek, the main tributary to the Salmon River.
EXPERIMENTAL ANALYSIS OF DESICCATION CRACK PROPAGATION IN CLAY LINERS1
Authors: Miller Carol J. , Mi Hong , Yesiller Nazli
Published: June 2007

ABSTRACT: A laboratory investigation on a scaled model of a landfill liner was conducted to provide data regarding the occurrence and extent of desiccation cracking of prototype liners. The crack intensity factor, CIF, was introduced as a descriptor of the extent of surficial cracking. CIF is defined as the ratio of the surface crack area A, to the total surface area of the clay liner, At. A computer aided image analysis program was used to determine CII’ values from scanned photographs of the desiccation process. The variation of the CII’ was related to duration of drying and measured soil moisture suctions.

The soil of this investigation experienced significant cracking, with crack widths approaching 10 mm in the first drying cycle and penetration through the entire 16 cm thickness. Crack propagation was limited to a very intense period of the desiccation process. Nearly 90 percent of the crack development occurred during a 19‐hour time period, although the total duration of the desiccation cycle was approximately 170 hours. The soil moisture suction changed by only 2 bars during the period of rapid crack growth, although it changed by more than 40 bars during the period of reduced growth.
HYDROLOGIC MODELING OF TWO GLACIATED WATERSHEDS IN NORTHEAST PENNSYLVANIA1
Authors: Srinivasan M. S. , Hamlett J. M. , Day R. L. , Sams J. I. , Petersen G. W.
Published: June 2007

ABSTRACT: A hydrologic modeling study, using the Hydrologic Simulation Program ‐ FORTRAN (HSPF), was conducted in two glaciated watersheds, Purdy Creek and Ariel Creek in northeastern Pennsylvania. Both watersheds have wetlands and poorly drained soils due to low hydraulic conductivity and presence of fragipans. The HSPF model was calibrated in the Purdy Creek watershed and verified in the Ariel Creek watershed for June 1992 to December 1993 period. In Purdy Creek, the total volume of observed stream‐flow during the entire simulation period was 13.36 × 106 m3 and the simulated streamflow volume was 13.82 × 106 m3 (5 percent difference). For the verification simulation in Ariel Creek, the difference between the total observed and simulated flow volumes was 17 percent. Simulated peak flow discharges were within two hours of the observed for 30 of 46 peak flow events (discharge greater than 0.1 m3/sec) in Purdy Creek and 27 of 53 events in Ariel Creek. For 22 of the 46 events in Purdy Creek and 24 of 53 in Ariel Creek, the differences between the observed and simulated peak discharge rates were less than 30 percent. These 22 events accounted for 63 percent of total volume of streamflow observed during the selected 46 peak flow events in Purdy Creek. In Ariel Creek, these 24 peak flow events accounted for 62 percent of the total flow observed during all peak flow events. Differences in observed and simulated peak flow rates and volumes (on a percent basis) were greater during the snowmelt runoff events and summer periods than for other times.
MODELING INFILTRATION WITH VARYING HYDRAULIC CONDUCTWITY UNDER SIMULATED RAINFALL CONDITIONS1
Authors: Gupta Ram , Rudra Ramesh , Dkkinson Trevor
Published: June 2007

ABSTRACT: Physically‐based models are extensively used to simulate the infiltration process under varied field conditions. Most models are based on the deterministic nature of input parameters related to the flow process (such as hydraulic conductivity). These models yield poor predictions of infiltration rates because they do not include the field‐scale variations of flow parameters. The paper presents an approach for integrating the field‐scale variability of hydraulic conductivity with an infiltration model to simulate infiltration under the rainfall conditions. A model describing the spatial structure of hydraulic conductivity has been developed using stochastic techniques. The stochastic structure of hydraulic conductivity was then incorporated in the Green‐Ampt and Mein‐Larson infiltration model. The model outputs on the instantaneous infiltration rates and cumulative infiltration were evaluated using the field infiltration data measured under simulated rainfall conditions. The results show that the combined model is capable of rep. resenting the instantaneous infiltration rates and cumulative infiltration of the study soils. The model may, therefore, be used to simulate the rainfall infiltration process for spatially‐variable soils under the field conditions.
MULTIVARIATE EXTREME VALUE DISTRIBUTION WITH MIXED GUMBEL MARGINALS1
Authors: Escalante‐Sandoual Carlos
Published: June 2007

ABSTRACT: Bivariate and trivariate distributions have been derived from the logistic model for the multivariate extreme value distribution. Marginals in the models are extreme value type I distributions for two‐component mixture variables (mixed Gumbel distribution). This paper is a continuation of the previous works on multivariate distribution in hydrology. Interest is focused on the analysis of floods which are generated by different types of storms. The construction of their corresponding probability distributions and density functions are described. In order to obtain the parameters of such a bivariate or trivariate distribution, a generalized maximum likelihood estimation procedure is proposed to allow for the cases of samples with different lengths of record. A region in Northern Mexico with 42 gauging stations, grouped into two homogeneous regions, has been selected to apply the models. Results produced by the multivariate distributions have been compared with those obtained by the Normal, log‐Normal‐2, log‐Normal‐3, Gamma‐2, Gamma‐3, log‐Pearson‐3, Gumbel, TCEV and General Extreme Value distributions. Goodness of fit is measured by the criterion of standard error of fit. Results suggest that the proposed models are a suitable option to be considered when performing flood frequency analysis.
GENERATING DESIGN HYDROGRAPHS BY DEM ASSISTED GEOMORPHIC RUNOFF SIMULATION: A CASE STUDY1
Authors: Lee Kwan Tun
Published: June 2007

ABSTRACT: The geomorphic instantaneous unit hydrograph (GIUH) may be one of the most successful methodologies for predicting flow characteristics in ungauged watersheds. However, one difficulty in applying the GIUH model is determination of travel time, and the other difficulty is the large amount of geomorphologic information required in the study watershed. Recently, using the kinematic‐wave theory Lee and Yen (1997) have analytically determined the travel times for overland and channel flows in watersheds. The limitation of using an empirical velocity equation to estimate the runoff travel time for a specified watershed is then relaxed. To simplify the time‐consuming work involved in geomorphic parameter measurement on topographic maps, the GIUH model is linked with geographic information systems to obtain geomorphic parameters from digital elevation models. In this paper, a case study performed for peak flow analysis in an ungauged watershed is presented. The geomorphic characteristics of the study watershed were analyzed using a digital elevation model and were used to construct the runoff simulation model. The design storm was then applied to the geomorphic runoff simulation model to obtain the design hydrograph. The analytical procedures proposed in this study can provide a convenient way for hydrologists to estimate hydrograph characteristics based on limited hydrologic information.
IMPACT OF RIPARIAN FOREST BUFFERS ON AGRICULTURAL NONPOINT SOURCE POLLUTION1
Authors: Snyder N. J. , Mostaghimi S. , Berry D. F. , Reneau R. B. , Hong S. , McClellan P W. , Smith E. P.
Published: June 2007

ABSTRACT: A field monitoring study of a riparian forest buffer zone was conducted to determine the impact of the riparian ecosystem on reducing the concentration of agricultural nonpoint source pollutants. Groundwater samples were collected from 20 sampling locations between May 1993 and December 1994, and analyzed for NO3‐N, PO4, and NH4‐N. Statistical analyses such as Friedman's test, cluster analysis, cross correlation analysis and Duncan's test were performed for the nutrient data. The study showed that the ripanan buffer zone was effective in reducing nitrate concentrations originating from upland agricultural fields. Instream nitrate concentrations were 48 percent less than those measured in the agricultural field. Reductions in concentrations in sampling locations at the wetland edge ranged from 16 to 70 percent. The mean nitrate concentrations in forested hill slope were 45 percent less than concentrations in a well located in an upland agricultural field. Meanwhile, the concentrations of phosphate and ammonia did not follow any specific spatial trend and were generally higher during the summer season for most sampling locations.
WIND GENERATED WAVES IN LAKE OKEECHOBEE1
Authors: Jin Kang‐Ren , Wang Keh‐Han
Published: June 2007

ABSTRACT: The study of wind generated waves is important because waves affect sediment resuspension in lakes. Measurements of wind velocity and wave elevation were made at three different stations in Lake Okeechobee. Significant wave heights were computed using a direct count from the recorded data, and verified by the root‐mean‐square value approach. The correlation between wind stress and significant wave height also was analyzed. The data revealed a strong correlation. In addition to field measurements, a Boussinesq‐type wind‐wave model was developed to simulate wind‐generated, long‐propagating waves. This model included the effects of wind stress and bottom viscous dissipation. Wave elevation and velocity field were evaluated numerically. A six‐day simulation using 1996 wind data was conducted. Simulated significant wave heights were found to agree reasonably well with measured values. A predictive wind‐wave model provides information about wind generated waves, which is used to compute bottom shear stresses required for sediment resuspension studies.
LAND SURFACE PARAMETERIZATIONS OF GCMs AND MACROSCALE HYDROLOGICAL MODELS1
Authors: Kite Geoff
Published: June 2007

ABSTRACT: Climatic variation and the possibility of anthropogenically‐caused climatic change have emphasized the need for global hydrological cycle models able to simulate the impacts of climate on the atmosphere, continents and oceans. To date, global atmospheric and oceanic models have been developed but, to the best of the author's knowledge, there are no continental hydrological models. Instead, hydrological models continue to develop at the catchment scale and the land phase component of the global hydrologic cycle is modeled as parameterizations within atmospheric models. The author argues that this is not the best solution; that the present land surface components of atmospheric models do not accurately model land phase hydrology and that, instead, atmospheric and oceanic models should be linked to continental‐scale hydrological models to form a true model of the global hydrological cycle.
MANAGING THE NATION'S WATER IN A CHANGING CLIMATE1
Authors: Lins Harry F , Stakhiv Eugene Z.
Published: June 2007

ABSTRACT: Among the many concerns associated with global climate change, the potential effects on water resources are frequently cited as the most worrisome. In contrast, those who manage water resources do not rate climatic change among their top planning and operational concerns. The difference in these views can be associated with how water managers operate their systems and the types of stresses, and the operative time horizons, that affect the Nation's water resources infrastructure. Climate, or more precisely weather, is an important variable in the management of water resources at daily to monthly time scales because water resources systems generally are operated on a daily basis. At decadal to centennial time scales, though, climate is much less important because (1) forecasts, particularly of regional precipitation, are extremely uncertain over such time periods, and (2) the magnitude of effects due to changes in climate on water resources is small relative to changes in other variables such as population, technology, economics, and environmental regulation. Thus, water management agencies find it difficult to justify changing design features or operating rules on the basis of simulated climatic change at the present time, especially given that reservoir‐design criteria incorporate considerable buffering capacity for extreme meteorological and hydro‐logical events.
A GIS‐BASED MODELING APPROACH FOR EVALUATING GROUNDWATER VULNERABILITY TO PESTICIDES1
Authors: Shukia S. , Mostaghimi S. , Shanholtz V O. , Collins M. C.
Published: June 2007

ABSTRACT: The Attenuation Factor (AF), a screening model, was used to evaluate the relative degree of vulnerability of groundwater to pesticide contamination in Louisa County, Virginia. For evaluating the contamination potential of pesticides, three scenarios of pesticide leaching represented by high, moderate, and low cases of degradation and sorption in the soil were considered. Data layers were overlaid within a Geographic Information System (GIS) for spatial computation of AF for the actual and 2m groundwater depths. This spatial database was divided into five contamination potential categories namely high, medium, low, very low, and unlikely, based on the numerical values of the AF for each cell (119 ha). The results for the three most mobile pesticides are presented in this paper. The performance of the AF model was evaluated by comparing its predicted results with the field data from an experimental watershed. The AF model was able to identify most of the frequently detected pesticides in the watershed. A sensitivity analysis was also performed. The results of this study provide information about the potential groundwater threat by pesticides to the citizens ahd decision‐makers in the County and can be used for formulating an appropriate land use management plan to protect the groundwater quality.
HEAD LOSS AT MANHOLES IN SURCHARGED SEWER SYSTEMS1
Authors: Wang K H. , Cleveland T G. , Towsley C. , Umrigar D.
Published: June 2007

ABSTRACT: A laboratory investigation was conducted to determine the head losses at sewer pipe junctions (manholes) under surcharged conditions. A physical model of a manhole/pipeline system was constructed for head‐loss measurements. Head‐loss coefficients were determined for a variety of outlet‐flow Reynolds numbers, surcharge levels, pipe sizes, flow configurations, and inlet‐flow rates. Empirical formulas were also developed to estimate head‐loss coefficients. The results indicate that head loss is insensitive to the amount of surcharge, but depends heavily on the flow configuration, relative flow rate, and the change of pipe diameter within the pipelines.
CENTRIFUGE MODELING OF ONE‐DIMENSIONAL SUBSURFACE CONTAMINATION1
Authors: Nakajima Hideo , Hirooka Akihiko , Takemura Jiro , Mariño Miguel A.
Published: June 2007

ABSTRACT: One‐dimensional contaminant transport through a saturated soil is modeled using a 1.2‐m radius geotechnical centrifuge. Small‐scale physical modeling in the centrifuge is achieved in relatively short time, at stress distributions that are similar to those experienced in the prototype (actual site). A 0.05 mol/l of sodium chloride solution is used as a contaminant and conductivity cells measure the concentration of the contaminant throughout the porous medium. Scaling analysis for centrifuge modeling and 1‐g modeling are briefly discussed and it is concluded that centrifuge modeling simulates the effect of molecular diffusion; however, scaling of the effect of mechanical dispersion may be violated in the centrifuge if the interstitial fluid velocity is high. Centrifuge test results show good agreement with the predicted relationship between the coefficient of hydrodynamic dispersion and the Peclet number using column tests. Centrifuge modeling can be used as a complement of numerical modeling although the effect of mechanical dispersion may be overestimated in the former.
USING ARTIFICIAL NEURAL NETWORKS TO ESTIMATE MISSING RAINFALL DATA1
Authors: Kuligowski Robert J. , Barros Ana P
Published: June 2007

ABSTRACT:Missing rainfall data from a time series or a spatial field of observations can present a serious obstacle to data analysis, modeling studies and operational forecasting in hydrology. Numerous schemes for replacing missing data have been proposed, ranging from simple weighted averages of data points that are nearby in time and space to complex statistically‐based interpolation methods and function fitting schemes. This paper presents a technique for replacing missing spatial data using a backpropagation neural network applied to concurrent data from nearby gauges. Tests performed on a sample of gauges in the Middle Atlantic region of the United States show that this technique produces results that compare favorably to simple techniques such as arithmetic and distance‐weighted averages of the values from nearby gauges, and also to linear optimization methods such as regression.
VERIFICATION OF THE RHEA‐OROGRAPHIC‐PRECIPITATION MODEL1
Authors: Hay Lauren E. , McCabe Gregory J.
Published: June 2007

ABSTRACT: Observed April 1 snowpack accumulations within and near the Gunnison River basin in southwestern Colorado are compared with simulations from the Rhea‐orographic‐precipitation model to determine if the model simulates reliable magnitudes and temporal and spatial variability in winter precipitation for the basin. Twenty simulations of the Rhea model were performed using‘optimal’parameter sets determined for 10‐kilometer (km) grids (10‐km by 10‐km grid cells) through stochastic calibration. Comparisons of Rhea‐model simulations of winter precipitation with April 1 snowpack accumulations at 32 snowcourse stations were performed for the years 1972–1990. For most stations and most years the Rhea model reliably simulates the temporal and spatial variability in April 1 snowpack accumulations. However, in general, the Rhea‐model underestimates April 1 snowpack accumulations in the Gunnison River basin area, and the underestimation is greatest for locations that receive the largest amount of snow. A significant portion of the error in Rhea‐model simulations is due to the calibration of the Rhea model using gauge‐catch precipitation measurements which can be as much as 50 percent below actual snowfall accumulations. Additional error in the Rhea‐model simulations is a result of the comparison of gridded precipitation values to observed values measured at points.
COMPARING THE PALMER DROUGHT INDEX AND THE STANDARDIZED PRECIPITATION INDEX1
Authors: Guttman Nathaniel B.
Published: June 2007

ABSTRACT: The Palmer Drought Index (PDI) is used as an indicator of drought severity, and a particular index value is often the signal to begin or discontinue elements of a drought contingency plan. The Standardized Precipitation Index (SPI) was recently developed to quantify a precipitation deficit for different time scales. It was designed to be an indicator of drought that recognizes the importance of time scales in the analysis of water availability and water use.

This study compares historical time series of the PDI with time series of the corresponding SPI through spectral analysis. Results show that the spectral characteristics of the PDI vary from site to site throughout the U.S., while those of the SPI do not vary from site to site. They also show that the PDI has a complex structure with an exceptionally long memory, while the SPI is an easily interpreted, simple moving average process.
SPATIAL MODELLING WITH GEOGRAPHIC INFORMATION SYSTEMS FOR DETERMINATION OF WATER RESOURCES VULNERABILITY APPLICATION TO AN AREA IN MASSIF CENTRAL (FRANCE)1
Authors: Laurent François , Anker Wolfram , Graillot Didier
Published: June 2007

ABSTRACT: A method for water resources protection based on spatial variability of vulnerability is proposed. The vulnerability of a water resource is defined as the risk that the resource will become contaminated if a pollutant is placed on the surface at one point as compared to another. A spatial modelling method is defined in this paper to estimate a travel time between any point of a catchment and a resource (river or well). This method is based on spatial analysis tools integrated in Geographical Information Systems (GIS). The method is illustrated by an application to an area of Massif Central (France) where three different types of flow appear: surface flow, shallow subsurface flow, and permanent ground water flow (baseflow). The proposed method gives results similar to classical methods of estimation of travel time. The contribution of GIS is to improve the mapping of vulnerability by taking the spatial variability of physical phenomena into account.
INTEGRATION OF WATER QUALITY MODELING, REMOTE SENSING, AND GIS1
Authors: Yang Ming‐Der , Merry Carolyn J. , Sykes Robert M.
Published: June 2007

ABSTRACT: Water quality modeling has been developed for more than three quarters of a century, but is limited to the study of trends instead of making accurate short‐term forecasts. A major barrier to water quality forecasting is the lack of an efficient system for water quality monitoring. Traditional water quality sampling is time‐consuming, expensive, and can only be taken for small sizes. Remote sensing provides a new technique to monitor water quality repetitively for a large area. The objective of this research is to use remotely sensed data in a water quality model ‐ QUAL2E ‐ in a case study of the Te‐Chi Reservoir in Taiwan. The water quality variables developed from the simulations are displayed in map form. The developed forecasting system is designed to predict water quality variables using remote sensing data as an input to initialize and update water quality conditions.
CHANNEL MORPHOLOGY EVOLUTION AND OVERBANK FLOW IN THE GEORGIA PIEDMONT1
Authors: Ruhiman Melanie B. , Nutter Wade L.
Published: June 2007

ABSTRACT: Historic changes in stream channel morphology were investigated in the Georgia Piedmont to better understand the hydrologic processes and functioning of the region's riverine systems. USGS gaging station data and channel geomorphology data were collected from thirty study sites in the Upper Oconee River Basin for flood frequency analysis. Historic and modern (i.e., present‐day) channel capacity discharge (i.e., overbank flow) was calculated using Manning's equation and historic channel cross‐section records. The recurrence interval for overbank flow was estimated for each site from flood frequency data. Results indicate that channel expansion has occurred throughout the basin, especially in upper reaches. Recurrence intervals for modern overbank events were variable and generally high ranging from < 2 to > 500 years for first to third order streams. They were less variable and lower for fourth and fifth order streams, ranging from < 2 to 3 years. Potential depositional thresholds were identified that exemplify the complex response of sediment distribution patterns throughout the basin. Results indicate overbank flows occur less frequently now than they once did due to historic accelerated sedimentation and subsequent channel expansion. One application of these findings is that these basin processes are likely applicable across the region and may impact the hydrologic functioning of associated Piedmont riverine wetlands that depend on flooding regimes.
AGRICULTURAL LAND USE IMPACTS ON BACTERIAL WATER QUALITY IN A KARST GROUNDWATER AQUIFER1
Authors: Boyer D. G. , Pasquarell G. C.
Published: June 2007

ABSTRACT: The impact on water quality by agricultural activity in karst terrain is an important consideration for resource management within the Appalachian Region. Karst areas comprise about 18 percent of the Region's land area. An estimated one‐third of the Region's farms, cattle, and agricultural market value are on karst terrain. The purpose of this study was to compare fecal bacteria densities in karst groundwater impacted by two primary agricultural land uses in central Appalachia. Fecal bacteria densities were measured in cave streams draining two primary land management areas. The first area was pasture serving a beef cow‐calf operation. The second area was a dairy. Neither area had best management practices in place for controlling animal wastes. Median fecal coliform and fecal streptococcus densities were highest in cave streams draining the dairy. Median fecal coliform densities in the dairy‐impacted stream were greater than 4,000 CFU/100 ml and the median fecal coliform densities in the pasture‐impacted streams were less than 10 CFU/100 ml. Median fecal streptococcus densities in the same streams were greater than 2,000 CFU/100 ml and 32 CFU/100 nil, respectively. A second dairy, with best management practices for control of animal and milkhouse waste, did not appear to be contributing significant amounts of fecal bacteria to the karst aquifer. It was concluded that agriculture was affecting bacterial densities in the karst aquifer. New management practices specifically designed to protect karst groundwater resources may be one way to protect the groundwater resource.
INTEGRATED WATER RESOURCES MANAGEMENT WHO SHOULD LEAD, WHO SHOULD PAY?1
Authors: Grigg Neil S.
Published: June 2007

ABSTRACT: Improving water management to meet future global needs will certainly require technical advances, but the main challenge is to integrate the viewpoints of diverse societal interests into decisions about allocation of water resources. The integration cannot be done solely by the market because it requires a balancing among interests which do not respond well to market forces, nor by the state alone because of institutional problems. The concept of “integrated water resources management” has been developed to provide the framework for the required balancing of interests, and, like similar concepts in industries other than water, it has a dual purpose ‐ to link stakeholders and apply best practices to management actions. To clarify the process of integrated water management, the paper focuses on two questions: who should lead integrated water resources management and who should pay for it? Several examples are given to illustrate a range of situations. The paper concludes with a call to improve paradigms of integrated water management, a proposition that water organizations should accept and budget for their external responsibilities as well as their direct missions, affirmation of the need for state and federal agencies to be involved with local interests, a call for better scientific and public information, and identification of the need for continued work to improve the process of integrated water management.