bluuebunny/crossref_metadata_2025 huggingface dataset:
MULTIOBJECTWE OPTIMIZATION OF RESERVOIR SYSTEMS OPERATION1
Authors: Ko Seok‐Ku , Fontane Darrell G. , Labadie John W.
Published: June 2007

ABSTRACT: Development of optimal operational policies for large‐scale reservoir systems is often complicated by a multiplicity of conflicting project uses and purposes. A wide range of multiobjective optimization methods are available for appraising tradeoffs between conificting objectives. The purpose of this study is to provide guidance as to those methods which are best suited to dealing with the challenging large‐scale, nonlinear, dynamic, and stochastic characteristics of multireservoir system operations. As a case study, the selected methodologies are applied to the Han River Reservoir System in Korea for four principal project objectives: water supply and low flow augmentation; annual hydropower production, reliable energy generation, and minimization of risk of violating firm water supply requirements. Additional objectives such as flood control are also considered, but are imposed as fixed constraints.
EFFECTS OF SLUDGE AND CHEMICAL FERTILIZER APPLICATION ON RUNOFF WATER QUALITY1
Authors: Mostaghimi S. , Younos T. M. , Tim U. S.
Published: June 2007

ABSTRACT: Simulated rainfall was used on experimental field plots to compare the effect of chemical fertilizer and sludge application on sediment, nitrogen, and phosphorus in runoff from no‐till and conventional tillage systems. Chemical fertilizer application under the no‐till system resulted in the least amount of total N and P in surface runoff. However, sludge application under the no‐till system resulted in the least amount of NO3‐N and sediment in surface runoff. The worst water quality scenarios were observed when either sludge or chemical fertilizer were surface‐applied under a conventional tillage system. Nitrogen losses from the conventional tillage system were minimized when sludge was incorporated into the soil. However, phosphorus and sediment yield from such a system were significantly higher when compared to phosphorus and sediment yield from the no‐till system.

The results from this study indicate that the use of sludge on agricultural land under a no‐till system can be a viable alternative to chemical fertilizer for nitrogen and phosphorus control in runoff. A more cautious approach is recommended when the sludge is incorporated into the soil in a conventional tillage system because of potential for high sediment and phosphorus yield in surface runoff.
ESTIMATING MARYLAND CRITICAL AREA ACVS IMPACT ON FUTURE NONPOINT POLLUTION ALONG THE RHODE RWER ESTUARY1
Authors: Houlahan John , Marcus W. Andrew. , Shirmohammadi Adel
Published: June 2007

ABSTRACT: This paper presents the results of an investigation of the effects of the Maryland Critical Area Act on generation of non‐point source loads of phosphorus, nitrogen, and sediment to the Rhode River estuary. The Simple Method model, the Marcus and Kearney regression model, and the CREAMS model were used to estimate annual loads under: (1) present conditions, (2) maximum land use development allowable under the Act, and (3) two sets of future land use conditions that might occur if the Act were not in place. Results indicate that the Critical Area Act can reduce the present generation of nonpoint nutrient and sediment loadings 20–30 percent from the regulated area. These reductions can occur while preserving agricultural lands and allowing limited residential and urban development. The decrease in nutrient loadings is primarily dependent upon implementation and enforcement of agricultural best management practices (BMPs). The BMPs could reduce present agricultural nutrient loadings by 90 percent to a level comparable to loadings from residential areas. The estimated effectiveness of the Critical Area Act is even greater when compared to potential future nutrient loadings if development in the area remains unregulated. Unrestricted residential and urban development could increase nutrient loadings by 200 percent to 1000 percent as compared to controlled development under Critical Area Act guidelines. The Critical Area Act primarily prevents these future increases by severely limiting woodland cutting, with lesser results obtained by requiring urban BMPs.
PARAMETER ESTIMATES FOR A GROUND WATER MODEL1
Authors: Condon M. R. , Traver R. G. , Fergusson W. B. , Chadderton R. A.
Published: June 2007

ABSTRACT: This paper presents a parameter sensitivity study of a two‐dimensional flow and transport model of a contaminated site. Hydrogeological and site data from previous investigations were used for calibration. The USGS contaminant transport model (MOC) was used.

After flow calibration to establish a reference model, parameters were varied to examine the effect each had on predictions of a contaminant plume. Hydrogeological parameters and a step size parameter were incrementally varied individually. Each result was compared to the reference model output to evaluate changes in concentration values and contaminant plume configuration.

The study indicated that a generally predictable trend can be established for some parameters not affected by pumping or similar high stresses. Ranges were identified to relate concentration error or plume change to the amount of parameter error. Some parameter perturbations produced distorted model responses at high stress locations. Porosity and anisotropy were found to be the most influential of the model parameters studied on the plume predictions. (KEY TERMS: ground water hydrology; hydrogeology; pollution modeling; water quality; model calibration.)
CENTRAL NEBRASKA RIVER BASINS, NEBRASKA1
Authors: Huntzinger Thomas L. , Ellis Michael J.
Published: June 2007

ABSTRACT: The Central Nebraska Basins (NAWQA) study unit includes the Platte River and two major tributaries, the Loup and Elkhorn Rivers. Platte River flows are variable in the western part of the study unit because of diversions, but the Loup and Elkhorn Rivers originate in an area of dune sand covered by grassland that generates consistent base flows. More frequent runoff in the eastern part of the study unit also sustains stream flow. Ground water in the study unit has no regional confining units and the system is a water table aquifer throughout. Macroinvertebrate and fish taxa at biological sampling sites in the state were related to stream flow. One of the four wetland complexes identified in the study unit includes habitat for threatened and endangered bird species. The study unit is an agricultural area that includes row crops, both irrigated and nonirrigated in the eastern and southern parts, and rangeland in the Sand Hills of the western part. A water quality assessment will be based on the differences in environmental setting in each of four subunits within the study unit.]
REVIEW OF A SEVENTEEN‐YEAR CHLOROPHYLL RECORD AS IT PERTAINS TO THE TROPIIIC STATUS OF LAKE OKEECHOBEE, FLORIDA, USA1
Authors: Phlips Edward J. , Aidridge F J. , Hanlon C.
Published: June 2007

ABSTRACT: A 17‐year record of chlorophyll a at eight limnetic sampling stations was used to evaluate putative changes in the trophic status of Lake Okeechobee, a shallow polymictic lake located in the subtropical environment of South Florida. Significant spatial differences were observed in the temporal patterns and variability of chlorophyll a concentrations. The highest chlorophyll a values were found in the northern and northwestern regions of the lake. The center of the lake, subject to high levels of non‐algal suspended solids, exhibited relatively low chlorophyll a values and coefficient of variation. The lowest chlorophyll a values were observed at the southernmost sampling station in the lake. This was also the station that showed a significant upward trend in annual mean chlorophyll a values over the 17‐year period of record. Examination of the relationship between chlorophyll a and three key environmental variables (i.e., total phosphorus concentration, phosphorus loading, and lake stage) revealed significant correlations at two out of the eight stations. The overall results of this study indicate that spatial and temporal disparities in the distribution and dynamics of chlorophyll a in Lake Okeechobee mandate more temporally and spatially intense approaches to the evaluation of trophic state than used in previous studies.
WATER TABLE INDUCED SHRUB‐HERBACEOUS ECOTONE: HYDROLOGIC MANAGEMENT IMPLICATIONS1
Authors: Groeneveld David P , Or Dani
Published: June 2007

ABSTRACT: Environmental factors were investigated across a shrub‐herbaceous ecotone (sharp zone of change) on a sloping site underlain by shallow groundwater on the arid floor of Owens Valley, California. Dominant plant species were salt rabbitbrush (Chrysothamnus nauseosus ssp. consimilis [E. Greene] Hall and Clements) and saltgrass (Distichlis spicata var. stricta EL.] E. Greene); typical of many similar habitats across the Great Basin. Historic air photographs were analyzed, and soil properties, water table levels and shrub and herbaceous cover were measured at discrete sample points. To investigate soil and vegetation spatial properties, sample points were apportioned on both sides of the ecotone. Land management practices and fire were ruled out as causal factors for the ecotone which remained stable through a 45‐year period of air photo record. Soil textural, chemical and hydraulic properties were similar across the ecotone and were uniform throughout the site. Only depth to the water table changed significantly in a gradient perpendicular to the ecotone. The shrub‐herbaceous ecotone was located where the water table depth fluctuated periodically between 0.8 and 1.2 m; deeper water tables than this range favors shrub cover while shallower depths favors meadow vegetation. When extrapolated to hydrologic management such as groundwater pumping, such a shallow depth and a narrow range of amplitude could restrict options for water development if maintenance of meadow vegetation is a goal.
ENVIRONMENTAL FACTORS INFLUENCING SUSPENDED SOLIDS IN THE LOXAIIATCHEE ESTUARY, FLORIDA1
Authors: Noel Jill M. , Chamberlain Robert H. , Steinman Alan D.
Published: June 2007

ABSTRACT: A study was initiated to examine the effects of wind speed, wind direction, freshwater inflow, and tide height on suspended solid concentration and distribution in the Loxahatchee estuary, Florida. Recent efforts to increase freshwater flows in this system raised concerns that suspended solid concentrations would increase as well, which might result in negative impacts for the estuary. The data indicated that total suspended solids (TSS) in the estuary are derived primarily from the inlet and not from freshwater tributaries. In addition, total suspended solids and volatile suspended solids were correlated strongly with salinity, suggesting that suspended sediments act conservatively throughout this system. No one environmental factor had an overwhelming influence on suspended solid concentration throughout the estuary; different regions of the estuary were influenced by different factors. Freshwater inflow was negatively related to TSS in the upper reaches of the estuary but was positively related to TSS in the central embayment region of the estuary. We attribute this latter finding to the fact that extremely high inflows both prevented the normal transport upstream of tidal borne suspended sediments and promoted mixing when the freshwater front moving downstream confronted the tidal front moving upstream. Wind speed, wind direction, and tide height had relatively small effects on TSS concentration but were most influential in reaches upstream of the central embayment, where tidal velocity begins to diminish.
WHO SHOULD MANAGE THE HIGH PLAINS AQUIFER? THE IRRIGATORS' PERSPECTIVE1
Authors: White Stephen E. , Kromm David E.
Published: June 2007

ABSTRACT: A state‐local partnership exists in Colorado and Kansas with respect to management of the High Plains aquifer. This paper examines 330 irrigators' attitudes about the locus‐of‐control for different management activities in the High Plains‐Ogallala region. Local control was preferred by most irrigators. The local district was most supported for 19 active management activities, whereas the state was favored for eight specific activities, primarily research efforts and water rights administration. Eight activities that had the potential for restricting water use were rejected in that irrigators indicated that no agency should be involved. Kansas and Colorado exhibited statistically significant preference differences for only five management options. A significantly higher percentage of those irrigators who preferred local control believed in sustainable management of the aquifer and aggressive groundwater management, and that their district served their interests.
RECOVERY OF “LOST” STORM WATER FROM LOCAL WASH BEDS1
Authors: Udall C. H.
Published: June 2007

ABSTRACT:Most of the precipitation that falls is unused because it never reaches a stream or recharges an underground supply. This storm water evaporates and is transpired and consumed by plants. Described below are pertinent legal principles and theconceptfor a small‐scale system to capture and store some of this “lost” storm water from the subflow of small gravelly washes that are not part of or connected with a stream system. The subsurface flow is interrupted by an elastomer faced earthen barrier (dam) and stored in a gravel bed. Both the barrier and the gravel storage bed are situated below the surface of the wash bed. If the gravel bed is not underlain by a natural substratum that is relatively impervious, it is either placed on a liner of suitable compacted clay or is underlain with an elastomeric membrane to limit the downward infiltration and loss of the stored water. A system may be used to capture and store sub‐flow after surface flow has ceased and during periods of drought; to supply household and irrigation water; to exercise Winters Doctrine rights; and to replace small dams and surface impoundments by underground storage of the captured water to ensure a more reliable and sanitary supply for livestock and wildlife. A system is most effective in desert regions where (or when) both stream and ground water are unavailable; where rainfall is infrequent, but in storms resulting in rapid runoff; and where land surface topography and morphology coincide to form sites that permit the productive use of a system. A system should not be installed without sound legal and hydrological advice. Careful engineering is essential to the safe and proper design of a system, especially its subsurface barrier.
GEOMORPHIC AND PEDOLOGIC INFLUENCE ON SMALL‐SCALE EPHEMERAL CHANNEL DIMENSION IN RANGELANDS1
Authors: George Heidi Wienert , Sidle Roy C.
Published: June 2007

ABSTRACT: Geomorphic processes may partly determine channel geometry. Soil particle uplift during freezing and thawing cycles and bank sloughing during wetting and drying periods were observed. Soil properties and channel dimension were measured to determine the dominant processes controlling channel geometry in eight small (mean area 0.096 km2) drainages in Logan Canyon, Utah. Soil cohesion was low (plasticity index > 15) for all but one of the drainages sampled. Basin scale geomorphic variables were examined to determine if they control channel dimension. Bankfull width was highly correlated to channel length and valley length with r2 values of 0.85 and 0.84, respectively. A strong canonical correlation (0.64) showed that distance from the watershed divide, bank liquid limit, and bank sand content were effective predictor variables of bankfull width and depth. The interrelations between geomorphic and pedogenic processes were the strongest determinants of ephemeral channel dimension in this study.
SIMULATING NITROGEN LOSSES FROM AGRICULTURAL LAND: IMPLICATIONS FOR WATER QUALITY AND PROTECTION POLICY1
Authors: Parsons Robert L. , Pease James W. , Bosch Darrell J.
Published: June 2007

ABSTRACT: EPIC, a soil erosion/plant growth simulation model, is used to simulate nitrogen losses for 120 randomly selected and previously surveyed cropland sites. Simulated nitrogen losses occur through volatilization, surface water and soil runoff, subsurface lateral flow, and leaching. Physical and crop management variables explain a moderate but significant proportion of the variation in nitrogen losses. Site slope and tillage have offsetting effects on surface and ground water losses. Nitrogen applications in excess of agronomic recommendations and manure obtained off the farm and applied to the sites are significant contributors to nitrogen losses. Farm characteristics such as production of confined livestock, total manure nitrogen available, and farm income per cropland acre explain a relatively large portion of the variability in manure nitrogen applied to survey sites. The results help to identify farm characteristics that can be used to target nutrient management programs. Simulation modeling provides a useful tool for investigating variables which contribute to agricultural nitrogen losses.
HYDROLOGIC BUDGET FOR A FRESHWATER MARSH IN FLORIDA1
Authors: Rushton Betty
Published: June 2007

ABSTRACT: Accurate water balance calculations are essential for water resource and environmental management decisions, but many of the terms used in the equation are difficult to measure. In this study, a method for measuring rates of evapotranspiration and net seepage from a freshwater marsh in southwest Florida is described. The results are compared to evaporation pan estimates as well as to calculations that balanced all the terms in the hydrologic budget. The measured rates of evapotranspiration showed a. distinct seasonal trend ranging from an average high of 0.24 in/d during July 1992 to a low of 0.06 in/d in January 1993. Evapotranspiration rates were higher than Class A evaporation pan measurements during July and August, indicating transpiration by plants exceeded evaporation by pans. Net ground water seepage flowed out of the marsh except during periods of high water table conditions. When all terms in the hydrologic budget were evaluated, the equation balanced on a yearly basis with an error of 2 percent, on a seasonal basis with errors less than 7 percent, but on a monthly basis errors were as great as 30 percent. Total annual rainfall on the marsh was 45 percent of the total marsh hydrologic input and was approximately equal to the loss by evapotranspiration of 41 percent.
RUNOFF SIMULATION USING RADAR RAINFALL DATA1
Authors: Peters John C. , Easton Daniel J.
Published: June 2007

ABSTRACT: Rainfall data products generated with the national network of WSR‐88D radars are an important new data source provided by the National Weather Service. Radar‐based data include rainfall depth on an hourly basis for grid cells that are nominally 4 km square. The availability of such data enables application of improved techniques for rainfall‐runoff simulation. A simple quasi‐distributed approach that applies a linear runoff transform to grid‐ded rainfall excess has been developed. The approach is an adaptation of the Clark conceptual runoff model, which employs translation and linear storage. Data development for, and results of, an initial application to a 4160 km2 watershed in the Midwestern U.S. are illustrated.
INTEGRATED RIVER BASIN OPTIMIZATION: MODELING ECONOMIC AND HYDROLOGIC INTERDEPENDENCE1
Authors: Ward Frank A. , Lynch Thomas P
Published: June 2007

ABSTRACT: This paper presents an integrated optimal control model that optimizes economic performance of reservoir management in watersheds in which there are significant economic and hydrologic interdependencies. The model is solved using the General Algebraic Modeling System (GAMS). Results show that application of this model to New Mexico's Rio Chama basin can increase total system benefits over historical benefits by exploiting complementarities between hydroelectricity production, instream recreation, and downstream lake recreation.
ALGAL BLOOM PROBABILITY IN A LARGE SUBTROPICAL LAKE1
Authors: James R. Thomas , Havens Karl E.
Published: June 2007

ABSTRACT: Algal blooms, defined as chlorophyll α concentrations greater than 40 μg l−1, are common in Lake Okeechobee, Florida. Using logistic regression techniques, we have developed equations that relate limnological variables to algal bloom occurrence in four distinct open‐water regions of this large shallow lake: central pelagic, northwest, southwest, and a transition region between the western and pelagic regions. Wind velocity and total phosphorus, which are closely related to resuspended material in the central region, are negatively related to algal bloom occurrence there. In the transition region, algal bloom occurrence is positively related to total nitrogen and wind velocity. Algal bloom occurrence is strongly and positively related to total nitrogen and total phosphorus concentrations in the western regions. The logistic regression model predicts an algal bloom probability greater than 95 percent in the northwest region when total phosphorus exceeds 0.10 mg l−1 and total nitrogen exceeds 2.5 mg l−1. In the southwest region the model predicts algal bloom probability of 100 percent when total phosphorus exceeds 0.10 mg l−1 and total nitrogen exceeds 2.8 mg l−1. Given 1994 mean total phosphorus concentrations of 0.05 and 0.04 mg l−1 in the northwest and southwest regions, respectively, total nitrogen would have to remain below 1.32 and 1.43 mg l−1, respectively, to keep the algal bloom probability below 10 percent. Because the lake is heterogenous, such nutrient standards should be considered on an in‐lake regional basis for Lake Okeechobee.
CUMULATIVE IMPACTS OF LANDUSE ON WATER QUALITY IN A SOUTHERN APPALACHIAN WATERSHED1
Authors: Bolstad Paul V , Swank Wayne T
Published: June 2007

ABSTRACT: Water quality variables were sampled over 109 weeks along Coweeta Creek, a fifth‐order stream located in the Appalachian mountains of western North Carolina. The purpose of this study was to observe any changes in water quality, over a range of flow conditions, with concomitant downstream changes in the mix of landuses. Variables sampled include pH, HCO32−, conductivity, NO3−−‐N, NH4+‐N, PO43−‐P, C1−‐, Na, K, Ca2+, Mg2+, SO42−, 5iO2, turbidity, temperature, dissolved oxygen, total and fecal coliform, and focal streptococcus. Landcover/landuse was interpreted from 1:20,000 aerial photographs and entered in a GIS, along with information on total and paved road length, building location and density, catchment boundaries, hydrography, and slope. Linear regressions were performed to relate basin and near‐stream landscape variables to water quality.

Consistent, cumulative, downstream changes in water quality variables were observed along Coweeta Creek, concomitant with downstream, human‐caused changes in landuse. Furthermore, larger downstream changes in water quality variables were observed during stormflow when compared to baseflow, suggesting cumulative impacts due to landscape alteration under study conditions were much greater during storm events. Although most water quality regulations, legislation, and sampling are promulgated for baseflow conditions, this work indicates they should also consider the cumulative impacts of physical, chemical, and biological water quality during stormflow.
DISTINGUISHING BETWEEN WATERSHEDS AND ECOREGIONS1
Authors: Omernik James M. , Bailey Robert G.
Published: June 2007

ABSTRACT:In an effort to adopt more holistic ecosystem approaches to resource assessment and management, many state and federal agencies have begun using watershed or ecoregion frameworks. Although few would question the need to make this move from dealing with problems and issues on a case by case or point‐type basis to broader regional contexts, misunderstanding of each of the frameworks has resulted in inconsistency in their use and ultimate effectiveness. The focus of this paper is on the clarification of both frameworks. We stress that the issue is not whether to use watersheds (or basins or hydrologic units) or ecoregions for needs such as developing ecosystem management and non‐point source pollution strategies or structuring water quality regulatory programs, but how to correctly use the frameworks together. Definitions, uses, and misuses of each of the frameworks are discussed as well as ways watersheds and ecoregions can be and have been used together effectively to meet resource management needs.
APPLICATION OF AN INTEGRATED BASIN‐SCALE HYDROLOGIC MODEL TO SIMULATE SURFACE‐WATER AND GROUND‐WATER INTERACTIONS1
Authors: Yu Zhongbo , Schwartz Franklin W.
Published: June 2007

ABSTRACT: Hydrologic models have become an indispensable tool for studying processes and water management in watersheds. A physically‐based, distributed‐parameter model, Basin‐Scale Hydro‐logic Model (BSIIM), has been developed to simulate the hydrologic response of large drainage basins. The model formulation is based on equations describing water movement both on the surface and in the subsurface. The model incorporates detailed information on climate, digital elevation, and soil moisture budget, as well as surface‐water and ground‐water systems. This model has been applied to the Big Darby Creek Watershed, Ohio in a 28‐year simulation of rainfall‐runoff processes. Unknown coefficients for controlling runoff, storativity, hydraulic conductivity, and streambed permeability are determined by a trial‐and‐error calibration. The performance of model calibration and predictive capability of the model was evaluated based on the correlation between simulated and observed daily stream discharges. Discrepancies between observed and simulated results exist because of limited precipitation data and simplifying assumptions related to soil, land use, and geology.
ENERGY BALANCE OF A CORN RESIDUE‐COVERED FIELD DURING SNOWMELT1
Authors: Sauer T J. , Hatfield J. L. , Prueger J. H. , Logsdon S. D.
Published: June 2007

ABSTRACT: Transport of agricultural chemicals in runoff and recharge waters from snowmelt and soil thawing may represent a significant event in terms of annual contaminant loadings in temperate regions. Improved understanding of the melt dynamics of shallow snowpacks is necessary to fully assess the implications for water quality. The objective of this study was to measure the energy balance components of a corn (Zea mays L.) stubble field during the melting of its snowcover. Net radiation (Rn), soil (G), sensible (H), and latent (Q) heat fluxes were measured in a field near Ames, Iowa, during the winter of 1994–1995. Energy consumed by melting including change in energy storage of the snowpack was determined as the residual of the measured energy balance. There was continuous snowcover at the field site for 71 days (maximum depth = 222 mm) followed by an open period of 11 days before additional snowfall and a second melt period. The net radiation and snow melt/energy storage change (5) terms dominated the energy balance during both measurement intervals. Peak daily sensible and latent heat fluxes were below 100 W m−2 on all days except the last day of the second melt period. There was good agreement between predicted and measured values of H and Q during the melting of an aged snow layer but poorer agreement during the melt of fresh snow. Both snowpacks melted rapidly and coincident changes in soil moisture storage were observed. Improved estimates of Q and H, especially for partially open surfaces, will require better characterization of the surface aerodynamic properties and spatially‐representative surface temperature measurements.
UNIT HYDROGRAPHS DERWED FROM THE NASH MODEL1
Authors: Boufadel Michel C.
Published: June 2007

ABSTRACT: Unit hydrograph ordinates are often estimated by deconvoluting excess rainfall pulses and corresponding direct runoff. The resulting ordinates are given at discrete times spaced evenly at intervals equal to the duration of the rainfall pulse. If the new duration is not a multiple of the parent duration, hydrograph interpolation is required. Linear interpolation, piece‐wise nonlinear interpolation and graphical smoothing have been used. These interpolation schemes are expedient but they lack theoretical basis and can lead to undesirable results.

Interpolation can be avoided if the instantaneous unit hydrograph (IUH) for the watershed is known. Here two issues connected with the classic Nash IUH are examined: (1) how should the Nash parameters be estimated? and (2) under what conditions is the resulting hydrograph able to reasonably represent watershed response? In the first case, nonlinear constrained optimization provides better estimates of the IUH parameters than does the method of moments. In the second case, the Nash IUH gives good results on watersheds with mild shape unit hydrographs, but performs poorly on watersheds having sharply peaked unit hydrographs. Overall, in comparison to empirical interpolation alternatives, the Nash IUH offers a theoretically sound and practical approach to estimate unit hydrographs for a wide variety of watersheds.
RECHARGE TO ALLUVIAL VALLEY AQUIFERS FROM OVERBANK FLOW AND EXCESS INFILTRATION1
Authors: Workman S. R. , Serrano S. E.
Published: June 2007

ABSTRACT: Recharge is an important parameter for models that simulate water and contaminant transport in unconfined aquifers. Unfortunately, measurements of actual recharge are not usually available causing recharge to be estimated or possibly added to the calibration procedure. In this study, differences between observed water‐table elevations and water‐table elevations simulated with a model based on the one‐dimensional Boussinesq equation were used to identify both the timing and quantity of recharge to an alluvial valley aquifer. Observed water table elevations and river stage data were recorded during a five‐year period from 1991 to 1995 at the Ohio Management Systems Evaluation Area located in south‐central Ohio. Direct recharge attributed to overbank flow during and shortly after flood conditions accounted for 65 percent of the total recharge computed during the five‐year study period. Recharge of excess infiltration to the aquifer was intermittent and occurred soon after large rainfall events and high river stage. Specification of constant recharge with time values in ground‐water simulation models seems inappropriate for stream‐aquifer systems given the strong influence of the river on water table elevations in these systems.
A CALIBRATION PROCEDURE USING TOPMODEL TO DETERMINE SUITABILITY FOR EVALUATING POTENTIAL CLIMATE CHANGE EFFECTS ON WATER YIELD1
Authors: Dietterick Brian C. , Lynch James A. , Corbett Edward S.
Published: June 2007

ABSTRACT:An evaluation was conducted on three forested upland watersheds in the northeastern U.S. to test the suitability of TOPMODEL for predicting water yield over a wide range of climatic scenarios. The analysis provides insight of the usefulness of TOPMODEL as a predictive tool for future assessments of potential long‐term changes in water yield as a result of changes in global climate. The evaluation was conducted by developing a calibration procedure to simulate a range of climatic extremes using historical temperature, precipitation, and streamfiow records for years having wet, average, and dry precipitation amounts from the Leading Ridge (Pennsylvania), Fernow (West Virginia), and Hubbard Brook (New Hampshire) Experimental Watersheds. This strategy was chosen to determine whether the model could be successfully calibrated over a broad range of soil moisture conditions with the assumption that this would be representative of the sensitivity necessary to predict changes in streamfiow under a variety of climate change scenarios. The model calibration was limited to a daily time step, yet performed reasonably well for each watershed. Model efficiency, a least squares measure of how well a model performs, averaged between 0.64 and 0.78. A simple test of the model whereby daily temperatures were increased by 1.7°C, resulted in annual water yield decreases of 4 to 15 percent on the three watersheds. Although these results makes the assumption that the model components adequately describe the system, this version of TOPMODEL is capable to predict water yield impacts given subtle changes in the temperature regime. This suggests that adequate representations of the effects of climate change on water yield for regional assessment purposes can be expected using the TOPMODEL concept.
WATERSHED AND LAKE WATER QUALITY ASSESSMENT: AN INTEGRATED MODELING APPROACH1
Authors: Mankin K R. , Koelliker J. K. , Kalita P. K.
Published: June 2007

Watershed planning groups and action agencies seek to understand how lake water quality responds to changes in watershed management. This study developed and demonstrated the applicability of an integrated modeling approach for providing this information. An integrated model linking watershed conditions to water‐quality of the receiving lake incorporated the following components: (1) an event‐based AGNPS model to estimate watershed pollutant losses; (2) annualization of AGNPS results to produce annual lake pollutant loadings; (3) a base flow separation package, SAM, to estimate base flow; (4) estimates of nutrients in base flow and point sources; and (5) linkage of watershed loadings directly to EUTROMOD lake water quality algorithms. Results are presented for Melvern Lake, a 28‐km2 multipurpose reservoir with a 900‐km2 agricultural watershed in east central Kansas. Reasonable estimates of current lake quality were attained using an average phosphorus availability factor of 31 percent to calibrate model results to measured in‐lake phosphorus. Comparison of a range of possible scenarios, including all cropland changed to no‐till (best case) and all CRP and good‐condition grasslands changed to cropland (worst case), indicated only a (4 percent change for in‐lake phosphorus and a (2 percent change for chlorophyll a. These results indicated that this watershed is not sensitive to projected changes in land use and management.
A FRAMEWORK OF ORDERED CLIMATE EFFECTS ON WATER RESOURCES: A COMPREHENSIVE BIBLIOGRAPHY1
Authors: Chalecki Elizabeth L. , Gleick Peter H.
Published: June 2007

ABSTRACT: An examination of the metadata for almost 900 bibliographic references on the effects of climate change and variability on U.S. water resources reveals strengths and weaknesses in our current knowledge. Considerable progress has been made in the modeling of climate change effects on first‐order systems such as regional hydrology, but significant work remains to be done in understanding subsequent effects on the second‐, third‐, and fourth‐order economic and social systems (e.g., agriculture, trade balance, and national economic development) that water affects. In order to remedy a recently‐revealed lack of understanding about climate change on the part of the public, climate and water scientists should collaborate with social scientists in illuminating the effects of climate change and variability on the systems that affect how and where most people live.
WHO GETS CLEAN WATER? AID ALLOCATION TO SMALL WATER SYSTEMS IN PENNSYLVANIA1
Authors: Jocoy Christine L.
Published: June 2007

ABSTRACT: Research on the condition of drinking water provision in the United States documents the inequitable financial impact of environmental regulations on small water systems (those serving 3,300 or fewer people). While a variety of federal and state financial assistance programs are available for water systems, few quantitative analyses have evaluated the success of these programs in alleviating the problems of small systems. A case study of the largest aid initiative for water supply infrastructure in Pennsylvania provides the empirical framework through which to analyze government funding opportunities for water systems. This study examines the allocation practices of the Pennsylvania Infrastructure Investment Authority (PENNVEST) to water systems of varying sizes. Utilizing data from PENNVEST applications and the Pennsylvania Department of Environmental Protection, the distribution of PENNVEST award recipients and denied applicants by size characteristics are compared. The study indicates that very small water systems (those serving 500 or fewer) do not apply for or receive funds with the same frequency as their larger counterparts. Understanding the allocation of awards from PENNVEST offers insight into the ability of small communities to access capital for water supply infrastructure.
WALNUT CREEK WATERSHED MONITORING PROJECT, IOWA MONITORING WATER QUALITY IN RESPONSE TO PRAIRIE RESTORATION1
Authors: Schilling Keith E. , Thompson Carol A.
Published: June 2007

ABSTRACT: Land use and surface water data for nitrogen and pesticides (1995 to 1997) are reported for the Walnut Creek Watershed Monitoring Project, Jasper County Iowa. The Walnut Creek project was established in 1995 as a nonpoint source monitoring program in relation to watershed habitat restoration and agricultural management changes implemented at the Neal Smith National Wildlife Refuge by the U.S. Fish and Wildlife Service. The monitoring project utilizes a paired‐watershed approach (Walnut and Squaw creeks) as well as upstream/downstream comparisons on Walnut for analysis and tracking of trends. From 1992 to 1997, 13.4 percent of the watershed was converted from row crop to native prairie in the Walnut Creek watershed. Including another 6 percent of watershed farmed on a cash‐rent basis, land use changes have been implemented on 19.4 percent of the watershed by the USFWS. Nitrogen and pesticide applications were reduced an estimated 18 percent and 28 percent in the watershed from land use changes.

Atrazine was detected most often in surface water with frequencies of detection ranging from 76–86 percent. No significant differences were noted in atrazine concentrations between Walnut and Squaw Creek. Nitrate‐N concentrations measured in both watersheds were similar; both basins showed a similar pattern of detection and an overall reduction in nitrate‐N concentrations from upstream to downstream monitoring sites. Water quality improvements are suggested by nitrate‐N and chloride ratios less than one in the Walnut Creek watershed and low nitrate‐N concentrations measured in the subbasin of Walnut Creek containing the greatest amount of land use changes. Atrazine and nitrate‐N concentrations from the lower portion of the Walnut Creek watershed (including the prairie restoration area) may be decreasing in relation to the upstream untreated component of the watershed. The frequencies of pesticide detections and mean nitrate‐N concentrations appear related to the percentage of row crop in the basins and subbasins.

Although some results are encouraging, definitive water quality improvements have not been observed during the first three years of monitoring. Possible reasons include: (1) more time is needed to adequately detect changes; (2) the size of the watershed is too large to detect improvements; (3) land use changes are not located in the area of the watershed where they would have greatest effect; or (4) water quality improvements have occurred but have been missed by the project monitoring design. Longer‐term monitoring will allow better evaluation of the impact of restoration activities on water quality.
METHOD TO IDENTIFY EFFECTWE RIPARIAN BUFFER WIDTHS FOR ATLANTIC SALMON HABITAT PROTECTION1
Authors: Haberstock Alan E. , Nichols Henry G. , DesMeules Mark P. , Wright Jed , Christensen Jon M. , Hudnut Daniel H.
Published: June 2007

ABSTRACT: Successful restoration of declining anadromous species is dependent upon effective riparian buffer zone management. Natural resource managers, policy developers and local conservation groups require science‐based information concerning the width at which a given buffer will be effective for its stated purpose. This paper summarizes a method developed in 1999 to determine effective riparian buffer widths for Atlantic salmon habitat protection as part of the Atlantic Salmon Conservation Plan for Seven Maine Rivers. A major assumption of the method is that no two buffers are alike with respect to their effectiveness and that various buffer characteristics dictate the required width for a given level of effectiveness. The method uses a predictive model that generates suggested riparian buffer widths as a function of specific, measurable buffer characteristics (such as slope, soil characteristics, and plant community structure and density) that affect buffer function. The method utilizes a variable‐width, two‐zone approach and specifies land uses that are consistent with desired buffer function within the two zones.
A TREE‐RING RECONSTRUCTION OF STREAMFLOW FOR THE COLORADO FRONT RANGE1
Authors: Woodhouse Connie A.
Published: June 2007

ABSTRACT: Water resource planning is based primarily on 20th century instrumental records of climate and streamflow. These records are limited in length to approximately 100 years, in the best cases, and can reflect only a portion of the range of natural variability. The instrumental record neither can be used to gage the unusualness of 20th Century extreme low flow events, nor does it allow the detection of low‐frequency variability that may underlie short‐term variations in flow. In this study, tree rings are used to reconstruct mean annual streamflow for Middle Boulder Creek in the Colorado Front Range, a semi‐arid region of rapid growth and development. The reconstruction is based on a stepwise regression equation that accounts for 70 percent of the variance in the instrumental record, and extends from 1703–1987. The reconstruction suggests that the instrumental record of streamflow for Middle Boulder Creek is not representative of flow in past centuries and that several low flow events in the 19th century were more persistent than any in the 20th century. The 1840s to early 1850s period of low flow is a particularly notable event and may have coincided with a period of low flow in the Upper Colorado River Basin.
CHARACTERISTICS OF LONG‐TERM FRESHWATER TRANSPORT IN APALACHICOLA BAY1
Authors: Huang Wenrui , Jones William K
Published: June 2007

ABSTRACT: Long‐term freshwater transport is an important factor affecting estuarine aquatic ecosystems. In this study, a primitive equation, prognostic, three‐dimensional, hydrodynamic model was applied to Apalachicola Bay, Florida, for the summer and fall seasons of 1993. In response to the river freshwater discharge, tide, and wind forces, the model simulations were used to characterize the long‐term freshwater transport processes in the bay. Analysis of spatial distributions of seasonal average salinity and currents shows that the long‐term freshwater transport was strongly affected by the forcing functions of wind and density gradient in the bay. Average freshwater input was approximately the same in the summer and fall seasons of 1993. However, in the summer season, more freshwater moved to the east direction due to the predominant wind from the west, while in the fall season more freshwater moved to the west in response to the wind primarily from the east. The water column was strongly stratified near the river mouth, and it gradually changed to well mixing near the ocean boundaries. Vertical stratification in the bay changed due to wind‐induced mixing and mass transport. Due to the density gradient effect, surface residual currents carrying fresher water were in the direction from the river toward the Gulf, while the bottom residual currents with saltier water entered the bay from the Gulf of Mexico.
MODELING RUNOFF FROM VARIABLE SOURCE AREAS IN HUMID, SHALLOW WATER TABLE ENVIRONMENTS1
Authors: Hernandez Tatiana , Nachabe Mahmood , Ross Mark , Obeysekera Jayantha
Published: June 2007

ABSTRACT: Variable Source Areas (VSAs) are zones with water saturated soils in forested wetlands fringing streams and creeks. Runoff from these areas is generated by saturation excess after a shallow water table rises and inundates the ground surface. In humid regions, like Florida and the Southeast, VSAs are believed to produce most of the runoff in shallow water table environments. Modeling the spatial extent and temporal fluctuation of a VSA is difficult because the formation of a VSA depends on a number of hydrological and morphological factors like rainfall intensity, soil texture, water table depth, and topographic attributes of the terrain. In this paper, we couple a digital elevation model with a two‐dimensional variable saturation model to illustrate the formation of a VSA at the hillside scale. The topography derived from the digital elevation model forms the upper domain geometry for the two‐dimensional finite element simulations of variable saturated flow. The objectives are: (1) to model the spatial and dynamic fluctuation of a VSA, and (2) to understand the roles of rainfall variability and terrain attributes on the formation of a VSA. Results show that hillsides with shallow water table depths, low saturated hydraulic conductivity, mild slopes, and concave slope curvature were more susceptible to runoff from a variable source. Runoff from a variable source showed little sensitivity to rainfall intensity. In general, landscapes with steep slopes generated a small VSA and a seepage face that vanished rapidly with time. In contrast, flat terrains are more amenable to VSA and retain ground surface inundation for longer periods of time.
WATERSHED AND INSTREAM IMPACTS ON THE FISH POPULATION IN THE SOUTH FORK OF THE CLEARWATER RIVER, IDAHO1
Authors: Papanicolaou A. N. , Bdour A. , Evangelopoulos N. , Tallebeydokhti N.
Published: June 2007

ABSTRACT: This paper presents the results of a statistical analysis performed for the watershed and stream corridor in the South Fork of the Clearwater River (SFCR) basin, in north central Idaho. The analysis was performed for 61 six‐field hydrological unit codes (HUCs) of the SFCR basin using an extensive record (up to 100 years) for 50 watershed and in‐stream parameters, including hydrologic, flow, fish, anthropogenic, and natural activity data. The objective of this research was twofold: first, the development of quantitative relations that describe the Index of Fish Density (IFD) of particular fish species as a function of watershed and instream parameters; and second, to provide a robust confirmation for the effects of some of these parameters, previously recorded by the fisheries profession, by using well established statistical techniques. The uniqueness of this work is the compilation and statistical analysis of large data sets to quantitatively describe the impacts of watershed and instream parameters on the IFD of all salmonids and specific fish species. Factor analysis was employed to regroup parameters that are highly correlated to each other into a set of single factors and to relate the IFD to these factors. Using factor extraction, 12 factors were developed from the 50 watershed and instream parameters. Multiple regression diagnostic tests indicated that only 7 of the 12 factors are strong predictors offish indicators. The strongest predictors are longitude, latitude, elevation, watershed gradient, and water temperature. The analysis indicated that the present model has reasonable predictive power, considering the uncertainty involved in estimating the interdependence of IFD with watershed parameters.