Nearby Gauges Research Articles

Relative Activity of Brook Trout and Walleyes in Response to Flow in a Regulated River

AbstractCoded electromyogram telemetry transmitters were used to examine the effects of varying flows on the relative activity of brook trout Salvelinus fontinalis and walleye Sander vitreus in a regulated river. The relative activity levels of two brook trout and two walleyes were continuously monitored for a minimum of 24 h, and measurements were compared with river flow values logged at nearby gauging stations. Generally, fish relative activity levels mimicked patterns of flow change, peaks in activity level corresponding to peaks in flow. Mean relative activity was generally greatest at extreme high (≥25‐m3/s) and low (<15‐m3/s) flows. High flows may have elicited hyperactivity (increased activity) as fish sought suitable refugia, increased activity to hold position in the water column, or increased feeding activity on increased levels of drifting invertebrates. Hyperactivity at low flows may have been caused by relocation due to habitat loss or ease of movement at lower flow regimes. Physiological telemetry provides researchers with a method of quantifying the immediate effects of flow changes on fish. Increasing our knowledge of the effects of river regulation on fish is essential to the development of more effective management strategies that balance ecology and economics.

Accuracy Evaluation of Rainfall Disaggregation Methods

Hourly rainfall depths are probably the most important data input for the simulation of watershed, instream, and water quality processes such as when using the Hydrological Simulation Program \IFORTRAN\N model. However, the density of stations measuring precipitation data on an hourly basis is low, so the disaggregation of daily rainfall values or the transfer of information from nearby stations is commonly applied. This investigation evaluated the accuracy of four methods for estimating hourly precipitation depths and assessed whether or not the accuracy of the estimates was a function of the distance between stations. Hourly rainfall records from 74 gauges located within or near the Chesapeake Bay watershed were used to evaluate the biases and accuracies of procedures for disaggregating measured daily depths into hourly amounts or transferring rainfall information for nearby gauges. None of the four methods provided accurate predictions of hourly rainfall, which suggests that it is difficult to get reliable estimates of hourly rainfall intensities by disaggregating daily totals or transferring hourly values from nearby gauges. However, the transfer of daily totals is more accurate than the estimation of hourly depths.

A Bayesian Joint Probability Approach for flood record augmentation

At‐site flood frequency prediction is often subject to large uncertainties because of the limited length of record available at the gauging station of interest. In many cases, however, one can find a nearby gauging station that has a considerably longer record. In this paper, we introduce a two‐site joint probability approach for the transfer of flood information between two stations. We assume that the annual maximum floods at the two stations follow a bivariate generalized extreme value distribution. We use a Bayesian procedure to estimate the parameters of the distribution by jointly using all the flood data available at the two stations. Efficient transfer of information is achieved by simultaneously carrying out (1) the inference of correlation of floods at the two stations, (2) the transfer of information between the two stations, and (3) the inference of the frequency distributions for the two stations.

A SIMPLE METHOD FOR ESTIMATING BASEFLOW AT UNGAGED LOCATIONS1

ABSTRACT: Baseflow, or water that enters a stream from slowly varying sources such as ground water, can be critical to humans and ecosystems. We evaluate a simple method for estimating base‐flow parameters at ungaged sites. The method uses one or more baseflow discharge measurements at the ungaged site and longterm streamflow data from a nearby gaged site. A given baseflow parameter, such as the median, is estimated as the product of the corresponding gage site parameter and the geometric mean of the ratios of the measured baseflow discharges and the concurrent discharges at the gage site. If baseflows at gaged and ungaged sites have a bivariate lognormal distribution with high correlation and nearly equal log variances, the estimated baseflow parameters are very accurate. We tested the proposed method using long‐term streamflow data from two watershed pairs in the Driftless Area of southwestern Wisconsin. For one watershed pair, the theoretical assumptions are well met; for the other the log‐variances are substantially different. In the first case, the method performs well for estimating both annual and long‐term baseflow parameters. In the second, the method performs remarkably well for estimating annual mean and annual median baseflow discharge, but less well for estimating the annual lower decile and the long‐term mean, median, and lower decile. In general, the use of four measurements in a year is not substantially better than the use of two.

Streamflow record extension using power transformations and application to sediment transport

To obtain a representative set of flow rates for a stream, it is often desirable to fill in missing data or extend measurements to a longer time period by correlation to a nearby gage with a longer record. Linear least squares regression of the logarithms of the flows is a traditional and still common technique. However, its purpose is to generate optimal estimates of each day's discharge, rather than the population of discharges, for which it tends to underestimate variance. Maintenance‐of‐variance‐extension (MOVE) equations [Hirsch, 1982] were developed to correct this bias. This study replaces the logarithmic transformation by the more general Box‐Cox scaled power transformation, generating a more linear, constant‐variance relationship for the MOVE extension. Combining the Box‐Cox transformation with the MOVE extension is shown to improve accuracy in estimating order statistics of flow rate, particularly for the nonextreme discharges which generally govern cumulative transport over time. This advantage is illustrated by prediction of cumulative fractions of total bed load transport.

USING ARTIFICIAL NEURAL NETWORKS TO ESTIMATE MISSING RAINFALL DATA1

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.

ESTIMATION OF WATER TEMPERATURE EXCEEDANCE PROBABILITIES USING THERMO‐HYDRODYNAMIC MODELING1

ABSTRACT: A continuous simulation approach is proposed for estimating water temperature exceedance probabilities using thermo‐hydrodynamic modeling. The approach uses (1) a deterministic unsteady flow and heat transport model, (2) continuous hydrological and meteorological data for a long historical period, and (3) synthetic records of tributary water temperatures and other model inputs. Representative historical records of streamflow, air temperatures, and other hydrometeorological variables are obtained from nearby gages. Stochastic modeling methods are used to construct synthetic records for other model inputs, including inflow water temperatures. An application of this deterministic‐stochastic approach is presented for a complex waterway in northeastern Illinois with heat discharges from several power plants and wastewater treatment plants. Statistical results from the continuous simulations are compared to results obtained from traditional event simulations. The application illustrates the information that engineers and biologists can obtain for (1) evaluating compliance with water temperature standards, and (2) assessing the effect of water temperatures on aquatic habitat.

Low Flow Estimation and Hydrogeology in a Chalk Catchment

Procedures to estimate low flow statistics at ungauged sites and their relation to hydrogeology are presented. The discussion is based on an example of a Danish chalk catchment of 242 km2, within which the climatic variation is small compared to the physiographical variation. The spatial and temporal variation of streamflow was studied using synchronous discharge measurements and the application of a numerical model. The synchronous discharge measurements showed the runoff is unequally distributed within the catchment and depends primarily on the regional hydrogeology, but also on the lithology of the valley deposits. The numerical model was used to obtain an understanding of the hydrogeological effect on the temporal variation of the runoff from small subcatchments. This was not possible from the discharge measurements because of the high uncertainty of estimating the difference in flow between two nearby gauging stations. The temporal variation was found to be strongly related to the hydraulic gradient along the river. A knowledge of catchment processes and variability of runoff from modelling studies is shown to assist in low flow estimation.

Seasonal and crop effects on soil loss and rainfall retention probabilities: An example from the U.S. Southern Piedmont

Soil loss from and rainfall retention on cropland during individual seasons vary from year to year. To quantify this variability for evaluation of soil and water related risks for different seasons and crops, probability distributions of soil loss and rain water retention are needed. In this study, probability distributions of soil loss and rainfall retention rates were computed using rainfall, runoff, and soil loss data from three field watersheds with Cecil-Pacolet soil (Typic Hapludults) in the Southern Piedmont of the United States. Long-term (34-year) rainfall records from a nearby gage were included in the computations. Resulting probability distributions were compared to evaluate risks of soil loss and low rainfall retention for different seasons and crops. Risks due to watershed differences in slope and in terrace and waterway conservation practices were also compared. These comparisons showed that soil loss risks are greater for the summer than for the winter crop season and greater for soybean ( Glycine max. L. Merr.) than for corn ( Zea mays L.). Considerable soil loss risk reduction was also observed for watersheds with less land slope and with terrace and grassed waterway installation. Risk of low rainfall retention was found to be less for the winter crop season than for the summer season. Rainfall retention risks for the winter crop season appeared to be unaffected by crop and watershed differences. For the summer crop season, however, risk of low rainfall retention was observed to be slightly higher for soybean than for corn and slightly lower for fields with terraces, grassed waterways, and lesser slopes. Soil loss and rainfall retention risks computed in this study can be coupled with economic costs for crop production and conservation planning.

Structure of the currents measured across a section of Johnstone Strait, Canada

A section of current measurements in Johnstone Strait is re-examined with the help of cross spectra and of a decomposition into orthogonal modes, the water levels at a nearby gauging station serving as a reference signal. The modes reveal that the estuarine circulation, present in the section, is modulated by the alternance between large and small tides, besides being disturbed by storms. The basic mode of the tidal currents is totally coherent with the vertical tide; two additional modes, one mainly diurnal, the other semidiurnal, help reproduce the profile of the currents measured in the section. The latter are interpreted as representing the part of the signal which is contributed by space and time fluctuations in the tidal flow. They make up some 25% of the tidal currents sensed in the section and are responsible for creating unusual gradients in phase in the analysed components. The stronger currents near the bottom are attributed to topographic effects and not to the presence of internal waves.

Rainfall retention probabilities computed for different cropping-tillage systems

Rainfall and runoff event data from several different cropping and tillage systems on three field-sized watersheds in the Southern Piedmont of the U.S.A. are used to estimate empirical probability distributions of the USDA Soil Conservation Service runoff curve number. Long-term rainfall records from a nearby gauge are also employed to obtain probabilities for rainfall event occurrence and depth. These probability distributions of runoff curve number and rainfall occurrence and depth are incorporated in a recursive computer procedure to compute estimated probability distributions of annual rainfall retention for the different cropping-tillage systems. Comparison of these estimated rainfall retention probability distributions shows a reduction in the risk for low rainfall retention with the installation of conservation tillage systems.

Estimating Soil Loss Probabilities for Southern Piedmont Cropping-Tillage Systems

ABSTRACT -Rainfall depth, runoff volume, peak runoff rate, and soil loss event data from three field-sized Piedmont watersheds under several different cropping-tillage systems are used to obtain estimated probability distributions of the Soil Conservation Service runoff curve number and the Universal Soil Loss equation combined C-P factor. In addition, long-term rainfall records from a nearby gage are employed to obtain probabilities of rainfall event occurrence and depth. These probability distributions of runoff and soil-loss model parameters and rainfall occurrence and depth are incorporated in a recursive computer procedure to compute estimated soil loss probability distributions for the different cropping-tillage systems. Comparison of these estimated probability distributions reveals cropping-tillage effects on soil loss probabilities and shows a definite reduction in soil loss risk for conservation tillage in the Southern Piedmont.

Estimation of groundwater recharge parameters by time series analysis

A model is proposed that relates water level fluctuations in a Dupuit aquifer to effective precipitaton at the top of the unsaturated zone. Effective precipitation, defined herein as that portion of precipitation which becomes recharge, is related to precipitation measured in a nearby gage by a two‐parameter function. A second‐order stationary assumption is used to connect the spectra of effective precipitation and water level fluctuations. Measured precipitation is assumed to be Gaussian, in order to develop a transfer function that relates the spectra of measured and effective precipitation. A nonlinear least squares technique is proposed for estimating parameters of the effective‐precipitation function. Although sensitivity analyses indicate difficulties that may be encountered in the estimation procedure, the methods developed did yield convergent estimates for two case studies.

APPLICATION OF THE STANFORD WATERSHED MODEL TO NIGERIAN WATERSHEDS1

ABSTRACT The Nigerian version of the Stanford Watershed Model was tested on two Nigerian watersheds. It was shown that model parameters for ungaged streams may be correlated on a regional basis from parameters of nearby gaged streams.

ESTIMATING THE T-YEAR FLOOD BY THE EXTENSION OF RECORDS OF PARTIAL DURATION SERIES

ABSTRACT The discharge likely to be exceeded once in T years on average is the ‘T-year flood’. This may be estimated in at least three ways: by fitting a probability distribution to the record of annual maximum discharges, by Monte Carlo simulation using a time-series model of the instantaneous peak discharges in short time-intervals (commonly days), or by a ‘partial duration series’ approach, in which a stochastic model is formulated for discharges exceeding a threshold. The latter method commonly assumes a Poisson distribution for the occurence of exceedances and an exponential distribution for the magnitudes of exceedances. The paper considers an extension of the partial duration series method to the commonly-encountered situation in which (a) the T-year flood must be estimated for a gauging site with a short record, and (b) a longer record is available for a nearby gauging site. The conclusion is that such an extension is possible if the following assumptions are valid: (a) the incidence of exceedances follows a bivariate binomial distribution for the period of common records; (b) the magnitudes of exceedances follow a bivariate exponential distribution.

Some measurements of the Alaska Stream with parachute drogues

On June 8–9, 1959, five parachute drogues were tracked for 25 hr near 175°W in the westward moving current south of the Aleutian Islands. The measured net flow at 5 m was 70, 79 and 83 cm/sec and at 300 m was 54 and 56 cm/sec. This flow is considerably higher than previous estimates for the Alaska Stream. Geostrophic flow was estimated from a line of oceanographic stations observed nearby in May and June 1959 and was found to be quite variable. One pair of stations yielded flow that was in very close agreement with the drogue measurements.The drogue data contain a periodic component that is predominantly alternating, east and west, with an average maximum speed of 25 cm/sec. The amplitude of the ocean tide was computed from the periodic currents; the various solutions were, except in one case, two to three times as great as the observed amplitude at nearby gages.

Absorption of Oxygen and Carbon Monoxide by Barium Alloy Getters

WAGENER1 has described a novel method of finding both the pumping speed and capacity of getters, and has made measurements2,3 with common gases and barium alloy getters of the type used in radio valves. The results obtained were conflicting. In the earlier paper2 it was reported that the speed of pumping depended upon the amount of ionizing electron current in a nearby diode or ionization gauge. Wagener's measurements were made in a range of electron current from 5 m.amp. to 20 m.amp. If these measurements are extrapolated to zero current they show that the speed of pumping is not then zero, contrary to the hypothesis suggested in the paper. In the later publication3 it was reported that the speed of pumping was about the same without, as with, an ionizing electron discharge. The present work was undertaken to decide between these contrary findings. It was decided to study the pumping of oxygen, because the chemical affinity of barium for this gas would make more remarkable any necessity for electron current.