Analysis Of Hydrological Data Research Articles

Epilithon and dissolved oxygen depletion in the Manawatu River, New Zealand: Simple models and management implications

The relationship between epilithic biomass and oxygen depletion was studied above and below wastewater discharges to the Manawatu River in an attempt to guide river management by defining the maximum respiration rates and the corresponding epilithic biomass consistent with maintenance of the legal minimum DO concentration of 5 g m −3. A computer model, which simulated the river DO under lowflow conditions, predicted that the maximum allowable respiration rate giving a dawn DO concentration of 5 g m −3 ranged from 20 g O 2 m −2 d −1 at 21°C to 24.5 g O 2 m −2 d −1 at 12°C. A multiple regression model developed from chamber measurements made in situ showed that the total biomass density and water temperature accounted for 73% of the variation in the respiration rate observed. When adapted to allow for respiration occurring in the water column, the model gave reasonably accurate predictions of respiration when checked against the whole river respiration rate measurements. Biomass densities, at which DO levels reach 5 gm −3 predicted using these models, ranged from 34 g ash free dry wt m −2 at 21°C to 143 g ash free dry wt m −2 at 12°C. Analyses of historical hydrological data and the results of epilithon growth measurements under a variety of water quality conditions in the Manawatu River indicate that the present management strategy of limiting instream BOD 5 to below 5 g m −3 but not limiting nutrient (N and P) levels will not prevent the occurrence in summer of the predicted nuisance biomasses and hence unacceptable deoxygenation.

La circulation générale en Méditerranée occidentale : Aperçu de nos connaissances et projets d'études

The general circulation in the Western Mediterranean Sea : broad outlines of our knowledge and action strategy. Valuable information has been recently obtained concerning the northern and southern parts of the Western Mediterranean Sea, mainly from remote sensing and current observations. The seasonal variability of the major currents in the Ligurian Sea, expected from the analysis of hydrological data, has been specified by direct measurements while the intensity and the barotropic character of turbulent (several days to a few weeks, several km to a few tens of km) phenomena during wintertime have been revealed. Moreover, the fundamental consequences, for the circulation of all the water masses and for the distribution of the biological and sedimentological characteristics as well, of the turbulent (a few weeks to several months, several tens to 1-2 hundreds of km) phenomena developping all year long in the Algerian Basin were more or less unexpected. Therefore, and mainly by taking into account the occurrence of such mesoscale turbulent phenomena, some aspects of the circulation have been either clarified or analysed in a new way and schematic maps have been proposed ; but numerous hypotheses have been put forward. In order to test some of them, studies really coordinated and based on as close as possible confrontations between observations and models, have been initiated ; the first of these studies will focus on the understanding of the reasons for the seasonal variability of the circulation.

Maximum entropy spectral analysis of hydrologic data

Determination of periodicities is a frequently encountered problem in stochastic analysis of hydrologic time series data. Conventional methods of spectral analysis such as those currently used in the analysis of hydrologic data have some long recognized disadvantages. The maximum entropy spectral analysis (MESA) method was developed as an alternative to conventional spectral analysis and has received considerable attention in exploratory geophysics. Several aspects of application of MESA to hydrologic time series are discussed in this paper. The performance of the MESA method is compared with the commonly used Blackman and Tukey method. MESA can be extended to obtain additional stochastic characteristics such as autocorrelation, partial autocorrelation, inverse autocorrelation, inverse partial autocorrelation, and cross spectra of time series data. Thus spectral analysis and computations related to stochastic model development may be integrated by using MESA. The simple relationship between maximum entropy and maximum likelihood spectra may be used to filter our pseudoperiodicities that occur in maximum entropy spectra estimated by using large filter orders.

Groundwater Flow and Sand Body Interconnectedness in a Thick, Multiple‐Aquifer System

Many so‐called sandstone aquifers are actually multiple‐aquifer systems consisting of discontinuous sand bodies distributed complexly in a matrix of lower‐permeability silts and clays. The arrangement and Interconnectedness of these various lithofacies strongly influence spatial patterns of hydraulic conductivity (K) and, in turn, groundwater flow and mass transport. A promising technique of estimating such patterns of K involves careful analysis of both subsurface geologic and subsurface hydrologic data. In this study the three‐dimensional distribution of K was estimated for a numerical flow model of part of the Wilcox aquifer system in Texas, using K data from core samples and pumping tests and more than 100 geophysical logs. The aquifer system, which is up to 320 m thick, consists of multiple, elongate sand bodies and silts and clays deposited in a fluvial environment and is similar to many other systems found in the Gulf Coast and other sedimentary basins. The resulting deterministic‐conceptual flow model demonstrates the importance and methods of incorporating geologic information in groundwater models. Flow in the aquifer is shown to be controlled not so much by K of the sands as by their continuity and Interconnectedness. Much of the aquifer system consists of large zones in which the fluvial channel‐fill sands are sparse and apparently disconnected, resulting in groundwater flow rates lower by a factor of 101 to 103 than in adjacent, well‐interconnected belts of fluvial channel‐fill sand belts. Modeling results also raise serious doubts regarding our ability to predict regional scale flow and mass transport in complex aquifers such as the Wilcox, using current technology. Though sand body Interconnectedness is critically important, it is also very difficult to estimate. One or two well‐connected sands among a system of otherwise disconnected sands can completely alter a velocity field. This is particularly true if the sands are connected vertically and nonzero vertical hydraulic gradients exist. Because the model is three‐dimensional, sensitivity of hydraulic head to heterogeneity or Interconnectedness is much less than normally observed in two‐dimensional models, and therefore heads computed by the model give little to no indication of the location of well‐interconnected zones. Thus such zones can easily go undetected, even in carefully calibrated models which yield reasonably accurate hydraulic heads. This is a significant point for modeling of solute transport.

Collection and Analysis of Hydrologic Data by Using a Personal Computer

Collection and Analysis of Hydrologic Data by Using a Personal Computer

1984 Horton Research Grant Award

The recipient of the 1984 Horton Research Grant Award is Javier F. Samper. Samper is a graduate student in the Department of Hydrology and Water Resources at the University of Arizona‐Tucson. The title of his research project is “A Methodology for the Combined Analysis of Hydrological, Hydrochemical, and Isotopic Data From Aquifers.” His research advisor is Shlomo Neuman.The objectives of his research are (1) to develop theoretical and computational tools for the spatial and statistical characterization of hydrochemical and isotopic data from aquifers and (2) to develop statistically based mathematical models incorporating hydrologic, chemical, and isotopic data to yield improved estimates of hydraulic and transport parameters as well as groundwater ages. Samper hopes to develop a workable mathematical framework which will allow a coordinated study of many types of hydrogeologic data, including hydraulic, chemical, and isotopic data. Such a systematically and mathematically based method of combined analysis for hydraulic, chemical, and isotopic environmental data is needed to develop a better conceptual understanding of the hydrogeology of any given area and to construct more reliable mathematical models for managing groundwater supply and quality.

Tests for detecting a shift in the mean of hydrological time series

A practical problem in time-series analysis of hydrological and meteorological data is to find statistical techniques for testing for an abrupt change in the mean at an unknown time. Suitable techniques have been developed in the situation of a single time series, { y i}. Attention is paid to the likelihood ratio statistic V and to a Bayesian statistic U. Complications arise if we want to test for a shift in the mean using a regression on a second correlated sequence, { x i}, because the critical values of the test statistic in general depend on the configuration of the x i's. For the statistic U, this problem can be solved using techniques similar to those for testing for serial correlation in least-squares regression. A so-called bounds test can be performed on the least-squares residuals. Unfortunately, there is quite a large possibility that this test is inconclusive. As an alternative to the bounds test, the statistic U can be applied to transformed residuals. The tests are illustrated with runoff and precipitation data for the Colorado River Basin, U.S.A., and the River Thames at Teddington, U.K.

Identification and prediction of nonlinear hydrologic systems by the filter-separation autoregressive (AR) method: Extension to hourly hydrologic data

Abstract In this paper, our method — from the hydrologic inverse detection method originally proposed for daily runoff data analysis — is extended to hourly hydrologic data analysis. A few modifications of the original inverse method (filter separation and autoregressive (AR) method) are necessary in order to apply it to hourly data. 1. (1) The cut-off frequency to separate the total runoff time series into component runoffs was determined by the slope of the semi-logarithmic plot of the recession curve. 2. (2) Coefficients of the autoregressive moving average (ARMA) model applied to each of the subsystems were determined by the least-squares criterion from the recession period data when rainfall stopped; thus the ARMA model is reduced to the AR model with a white-noise error. A remaining coefficient to be multiplied by the rainfall (input) is obtained by the continuity condition of effective rainfall and runoff. The conclusions of this analysis are as follows: 1. (1) Nonlinear hourly hydrologic systems are easily and precisely identified and predicted by the present method. 2. (2) Each subsystem of surface runoff, interflow and groundwater runoff is linear; the nonlinearity of the rainfall-runoff system is caused mainly by the nonlinearity of the separation of rainfall into component rainfalls. The nonlinear separation rule of rainfall into rainfall components is derived from inversely estimated rainfalls. 3. (3) Time series of hourly rainfalls can be inversely estimated from hourly runoff by this method and it compares well with the observed effective precipitation time series regardless of the size of watershed.

Analyse des param�tres hydrobiologiques dans la remont�e de Cabo Frio (Br�sil)

South Atlantic Central Waters (SACW) upwell close to Cabo Frio (Brazil, Rio de Janeiro) shore. The resultant typical hydrobiological conditions were studied at an anchorage station over an annual cycle from February 1973–February 1974. Multivariate analyses of hydrological and planktonic data revealed the structure of the ecosystem and the factorial relations governing its dynamics. Alternation, superposition or mixing of the water masses of different origin (Brazil current, coastal, SACW) constitute the most important factors responsible for the great hydrobiological variability observed in the study area. Spasmodic changes in wind direction and force are superimposed on a seasonal trend of more frequent upwelling in summer than during the rest of the year. The deep water is characterized by temperatures of <18°C, nitrate contents of 10 μg-at l-1 and by organic matter mainly composed of detritic elements from the shelf. Temperature variations together with nutrient contents (NO3 or PO4) reflect variations in primary biomass at the surface but not at 50 m depth, where detrital matter precluded valid measurements. Water of the Brazilian Current (salinity ≧36.0‰) frequently mixes with deep water of the thermal front, or with coastal water (<35.0‰) which invades the area when south-west winds prevail. This lower-salinity water is rich in seston particles. During the study period, primary biomass was relatively low due to eutrophication. We observed less than 3 μg l-1 chlorophyll and 106 phytoplankton cells per litre: the phytoplankton populations were highly diversified, indicating an advanced degree of complexity and evolution of this ecosystem. The observed formation of a thermocline constitutes an important inducing factor for an algal bloom. Simultaneous phyto- and zooplankton maxima would induce an increased grazing rate by herbivorous zooplankton which would also partly explain the relatively low level of primary biomass. Zooplankton is as abundant here as in other great upwelling regions: 100 organisms l-1 and 200 mg organic matter m-3.

Characterization of Earth Materials Properties for Conceptual Design of an Exploratory Shaft, Richton Dome, Mississippi

ABSTRACTPreliminary Exploratory Shaft design studies have been performed for representative sites in all salt basins within the NWTS Program. These studies have been based on data which are not site specific. Earth materials overlying the Richton Dome were characterized by analysis of geotechnical and hydrological data that had been acquired for site selection purposes. Data sets were reorganized, reinterpreted and evaluated in light of published empirical correlations, known constituative relations, experience with other sites, and engineering judgment.Geotechnical properties were assessed from geophysical logs, lithologic sample descriptions, and limited blowcount, grain size and pump test data. These properties included grain size, plasticity, unit weight, moisture content, bulk density, porosity, shear strength, elasticity, permeability, and saturation. Additionally, chemical and thermal properties were estimated and the local hydrologic flow properties were addressed.The analyses allowed heretofor unrecognized lithologic material groupings (defineable layers and sublayers) to be identified based on similarities in physical properties. Subsurface conditions, as interpreted, pose no unique excavation problems. However, the analysis identified some potential issues which had not been previously recognized and gave confidence that other previously assumed potential problems may not exist. Future work for subsequent design should focus on shaft wall stability, ground-water inflow, expansive clays, and the impacts of long-term exposure of the materials.

A Microprocessor Based Water Level Recorder and Sampler Controller

ABSTRACT RESEARCH to study the nature and extent of non-point sources of pollution from surface water runoff, including agricultural operations, requires instrumenta-tion that records intermittent runoff water levels and ac-tivates sampling equipment (Johnson et al., 1978). Ac-quisition and analysis of hydrologic data using current techniques is a time consuming and expensive process which demands better data collection and reduction pro-cedures.

Stormwater Analysis and Prediction in Houston

Analyses of available stormwater hydrologic and water quality data for several Houston area watersheds yielded direct linear relationships between pollutant mass loading rates and cumulative storm runoff volume. These relationships were then used to rank the watersheds on a pollutant load per unit runoff basis, and to calculate total annual pollutant loads for each area. Further, a plot of dimensionless cumulative flow versus the dimensionless cumulative flux provides a quantifiable means to evaluate the first flush, allowing comparison of this effect between watersheds. Finally, the developed load-runoff relationships provide the basis for a simple, yet effective method of predicting pollutant mass flows for individual or sequential storm events.

Network characteristics in suburbanizing streams

Analysis of hydrologic, geomorphic, and suburbanization data from a small instrumented drainage basin near Iowa City, Iowa, indicates that channel networks are radically altered when suburban development overtakes a drainage basin. Changes in channel networks are such that the network becomes much more efficient in collecting water quickly, so that lag time and kurtosis of storm hydrographs are altered to produce the familiar flash floods of urban areas. The data show that network changes are closely associated with lag time and kurtosis of storm hydrographs and suggest that corrective measures should be concentrated on the internal links of the network. Changes in characteristics of channel networks should be considered in addition to changes in areas of impervious surfaces when the hydrologic impact of suburbanization is assessed.

INSTANTANEOUS UNIT HYDROGRAPHS, PEAK DISCHARGES AND TIME LAGS IN URBAN BASINS

ABSTRACT The effects of urbanization of a basin on the runoff have been investigated in the past by the use of linear conceptual models in which the time lag appears as an important parameter. However, in this approach the effects of noise in the data, of sampling rate, of errors due to the lack of synchronization between the effective rainfall and runoff on the instantaneous unit hydrograph do not become readily apparent. A case in which the cumulative effects of these factors are predominant is presented as an example of the possible difficulties which might be encountered in the analysis of urban hydrological data by the unit hydrograph method. The disadvantages of relating the peak discharge, the time to peak discharge and the time lag to the physiographic characteristics alone have been discussed. Alternative regression relationships which involve storm characteristics along with the physiographic characteristics to estimate the peak discharge, time to peak discharge and time lag have been presented.

Hydro‐Analyses for the Engineer

This text, like many European textbooks, would have to be considered by American standards as a ‘cookbook’ approach to engineering hydrology. The major methods used in the engineering analysis of hydrologic data are clearly presented and well illustrated with examples. How ever, the only information given is how to perform these analyses.The book is an authorized translation from the Czech language edition of Nemec's text Inženýrská Hydrologic first published by SNTL, Prague, in 1964. Although not specifically stated, some updating has been done, consisting mainly of insertions in the text of references to WMO publications. (Nemec is presently Chief of the Hydrology and Water Resources Department of the World Meteorological Organization.)

Runoff estimation for very small drainage areas

Analyses of hydrologic data from high‐intensity short‐duration storms on very small drainage areas having varying physical characteristics indicated that a 1‐minute unit hydrograph could be used as the basis for generting runoff from an effective rainstorm input. The single parameter of the unit hydrograph (time constant K) was shown to be related to the physical characteristics of the drainage area. No evidence of the correlation between K and the storm pattern was discovered. Procedures are given for estimating net storm inputs.

On the Efficient Use of High Aswan Dam for Hydropower and Irrigation

With, the completion of the High Aswan Dam it will be possible to use the water of the Nile River in many different ways for different beneficial purposes. The selection of the best method of operating the dam and developing new resources to speed economic growth and social progress is of great importance to the United Arab Republic. A large sustained multidisciplinary effort combining economic analysis, engineering design, and governmental planning will be required. It is the purpose of this paper to describe some analytical methods that will be useful in this undertaking. A mathematical model for computer studies is developed to elucidate and quantify the relations between the variables pertaining to agricultural and power uses. Other functions of the dam such as flood protection and improvement of navigation are not examined in this initial study. However, it will be possible to investigate them in a more comprehensive model using similar mathematical methods. In its present form the model is designed to use standard linear programs so that operations studies can be made without recourse to sophisticated computer techniques. The model incorporates some of the chief factors affecting efficiency of multipurpose operation for the generation of hydroelectric power and for increasing the agricultural production of the United Arab Republic. The formulation provides a logical framework on which other functions may be added at a later stage. In the last section of this paper some of the most important modifications and elaborations are discussed. The numerical data used in the present study are based on a preliminary analysis of available hydrological and economic data. Considerably more statistical analysis will be required to develop valid numerical data for the model so that reliable inferences and rational decisions can be made. The computational results at this stage are useful only in indicating the kind of inferences and the type of information that may be obtained in a more definitive study.

Spectral Analysis of Hydrological Data

Spectral Analysis of Hydrological Data

Infiltration Capacities of Fayette Silt Loam From Analysis of Hydrologic Data

Infiltration Capacities of Fayette Silt Loam From Analysis of Hydrologic Data

Discussion of “Effect of various hydro‐climatic factors on snowmelt runoff”

This report of an investigation to determine a multiple correlation equation for use in relating various hydrologic factors is an extremely worthwhile presentation. As the authors point out, there have been numerous papers reporting results of statistical analyses of hydrologic data. However, there have been too few papers devoted to a description of the techniques used in selecting and designing empirical equations for use in regression analysis in hydrologic studies. The recent rapid increase in the application of electronic computers emphasizes the need for increased familiarity with basic mathematical and numerical methods.