摘要:

Bathymetric maps are the source of most morphometric data used in limnological, hydrological, and sedimentological contexts. The reliability of the morphometric data will depend on the accuracy of the bathymetric map, which in turn will depend on the intensity of the hydrographic survey. The aim of this work is to analyze thoroughly the relationship between intensity of survey, aim of survey, and yield of survey and to deduce a formula which may be used to express these concepts quantitatively so that hydrographic surveys can be executed in an optimal manner. An empirical formula which may be utilized to estimate the length of contour lines of a given bathymetric map from the hypsographic curve is also introduced.

ISSN:0043-1397    

DOI:10.1029/WR014i004p00545

年代:1978

数据来源: WILEY

摘要:

Formulae were derived for prediction of ponding time and cumulative infiltration following ponding under a condition of piecewise variable and even intermittent rainfall. The derivations do not assume immediate saturation at the surface or a piston displacement of air by water; they include the viscous flow of air. The results were compared with experimental data of James and Larson for two conditions: constant rainfall and intermittent rainfall. The proposed formulae are simple to use, requiring no complex solution of a partial or even an ordinary differential equation. The numerical calculations presented in the paper were performed with a small pocket calculator. The agreement with experimental data is good.

ISSN:0043-1397    

DOI:10.1029/WR014i004p00561

年代:1978

数据来源: WILEY

摘要:

Sampling frequency for a water quality monitoring network is presented, and for illustrative purposes the criterion is applied to the Massachusetts portion of the Connecticut River basin. The proposed frequency criterion is based upon the assumption that the primary objectives of future river quality monitoring networks are the determination of ambient water quality conditions and an assessment of yearly trends rather than detection of stream or effluent standards violations. The sampling frequency criterion is derived as a function of the random variability of the river flow. The criterion is specifically related to the magnitude of the expected half width of the confidence interval of the mean of the random component of the annual statistic‐mean log river flow. The appropriate sampling intervals (at each sampling station within the river basin) are determined by specifying equality of this confidence interval half width, which insures a uniform reliability of the annual statisti

ISSN:0043-1397    

DOI:10.1029/WR014i004p00569

年代:1978

数据来源: WILEY

摘要:

An adaptive unbiased recursive prediction algorithm, based upon the state space description of hydrologic systems, is discussed. Discrete linear systems with white Gaussian disturbances are considered. The algorithm allows for short‐term structural and parameter changes due to random environmental effects. A prediction model is set up from a representation of the rainfall‐runoff processes with the unknown parameters modeled by a random walk. The predictions are obtained by the use of linear Kaiman filters where the unknown noise covariance matrices are also adaptively estimated. The behavior of the adaptive prediction algorithm is illustrated by a real‐world example taken from rainfall‐runoff flood fore

ISSN:0043-1397    

DOI:10.1029/WR014i004p00577

年代:1978

数据来源: WILEY

摘要:

The relationship between the longitudinal and transverse dispersion coefficients (DLandDτ) and the pore water velocity (υ) and the effective diffusion coefficient (De) was determined for 0.01<υ<0.28 cm/min in a vertical unsaturated column (L= 23 cm) of C horizon Plainfield sand. The inflow and outflow control systems on the soil column consisted of rows of porous ceramic tubes with individual adjustable pressure controls. Uniform inflow and outflow were achieved across the column, and υ was maintained constant during each experiment. An analysis of the transverse spread produced indicated that the effect of apparatus‐induced dispersion was<10%.DL(cm2/min) was linearly related to υ (cm/min) (DL= 0.216υ + 0.0032;r2= 0.90). Slightly largerDLwas found in experiments with H2O replacing Cl than in experiments with Cl replacing H2O.DLat the lowest υ was 2 orders of magnitude greater thanDe.DT(cm2/min) was essentially independent of υ(DT= 0.0035υ + 0.0031;r2= 0.15) and was about 2 orders of magnitude greater thanDeat the lowest υ studied. The spread of tracer at the outflow was inversely proportional to υ, and transverse dispersion had reduced the concentration peak of the inflow by 84% atL= 23 cm and υ = 0.01 cm/min. The ratioDL/DTwas proportional to υ and ranged from ∼ 1 (υ = 0.01 cm/min) to ∼2

ISSN:0043-1397    

DOI:10.1029/WR014i004p00582

年代:1978

数据来源: WILEY

摘要:

Nitrogen and phosphorus in precipitation and dry fallout (aeolian sources), as well as thepH of rainfall, were measured over Harp Lake in Ontario during 1974. Weighted mean concentrations of totalNand totalPduring the ice‐free period of collection were 1.91 mgN/l and 0.105 mgP/l. Winter concentrations of totalNwere similar, but total P concentrations were much lower, averaging 0.013 mg/l in fresh snow. Total atmospheric loading of P to the lake was 74.4 mg P/m2yr, and the totalNloading was 1600 mgN/m2yr. About 52%, or 39.0 mgP/m2yr, of the total P loading from the atmosphere was total dissolved P (0.22‐µm filtrate), and 28%, or 20.6 mg P/m2yr, of the total P loading was dissolved reactive P (‘Orthophosphate’ P). Dissolved inorganicNloading at 1010 mgN/m2yr comprised about 63% of the totalNloading from the atmosphere. Pollen, from a variety of trees surrounding the lake, contributed about 20% of the total P input. ThepH of rainfall samples ranged from 3.2 to 5.1 with a median value of 3.9

ISSN:0043-1397    

DOI:10.1029/WR014i004p00589

年代:1978

数据来源: WILEY

摘要:

The water pressure regime of a quasi steadily melting homogeneous and isotropic snowpack is derived from Darcy's equation and from an experimental determination of the permeability‐pressure relation for snow. The derivation demonstrates that at a given melt rate, (1) significant water pressure gradients are confined to the base of the snowpack and (2) the snow water pressure at higher levels is independent of depth and equal to a characteristic value called the gravity flow pressure, which is a function of the melt rate and wetting history of the snow. Simple and inexpensive tensiometers were used to measure the water pressure variations in a deep snowpack. Diurnal pressure changes were found to be about 300Nm−2in amplitude within the ripe snow. Layering resulted in a scattering of the water pressures along the vertical direction. Such simple tensiometer measurements can now be used with the above derivation to provide field measurements of the permeability of different types of s

ISSN:0043-1397    

DOI:10.1029/WR014i004p00593

年代:1978

数据来源: WILEY

摘要:

The soil moisture characteristic may be modeled as a power curve combined with a short parabolic section near saturation to represent gradual air entry. This two‐part function—together with a power function relating soil moisture and hydraulic conductivity—is used to derive a formula for the wetting front suction required by the Green‐Ampt equation. Representative parameters for the moisture characteristic, the wetting front suction, and the sorptivity, a parameter in the infiltration equation derived by Philip (1957), are computed by using the desorption data of Holtan et al. (1968). Average values of the parameters, and associated standard deviations, are calculated for 11 soil textural classes. The results of this study indicate that the exponent of the moisture characteristic power curve can be predicted reasonably well from soil texture and that gradual air entry may have a considerable effect on a soil's wetting front

ISSN:0043-1397    

DOI:10.1029/WR014i004p00601

年代:1978

数据来源: WILEY

摘要:

Parlange's (1976) model corresponds to a special case of Mualem's similarity hypothesis ƒ(ψw, ψd) =h(ψw)l(ψd) in whichh(ψ) is set at unity for all ψ values. Interpreted in terms of the soil water domain theory this assumption implies that the relative pore volume of the domains is distributed uniformly in respect to the wetting radius (or to ψw). In this paper the proper mathematical equation is derived for calibrating the model from the experimental main drying curve. The applicability of Parlange's model for the soil water hysteresis is theoretically analyzed and extensively tested for different types of porous media. Theoretical hysteretic curves derived by direct implementation of Parlange's model are compared with experiments. These comparisons show that Parlange's model contradicts well‐known properties of the soil moisture characteristics. The good results reported by Parlange are not obtained when actual measured curves of the hysteresis loop are used. Whether the main branch of hysteresis for wetting or for drying is used in calibration, one obtains badly distorted shapes of hysteresis curves. Parlange's suggestion for calibrating the model on the basis of the main drying curve plus one additional point from the main wetting curve is considered too arbitrary to be

ISSN:0043-1397    

DOI:10.1029/WR014i004p00605

年代:1978

数据来源: WILEY

摘要:

This paper describes a physical laboratory model to study two‐dimensional transient water and solute transport in unsaturated soil, including water uptake by roots. It features an automatic two‐dimensional gamma ray attenuation scanner for measuring soil water content. Automation is obtained with a simple closed loop control circuit. After a gamma count is transmitted to the teletypewriter, a signal is sent to the hydraulically moved scanner to search for the next grid point. Upon arrival the scanner sends a signal back to initiate another data acquisition sequence, and so on. In this way, synchronization between counter and scanner is assured independent of counting time, travel time, configuration of grid points, temporary slowdown, etc. It also eliminates dead time between grid points for any recording pattern. Grid points are established by an array of holes that trap the core of a solenoid actuator. The configuration of grid points can be changed easily by opening and closing the desired holes. This mechanical trapping was found to be simpler and more accurate than a potentiometric control. The soil water flow model is constructed in modules. It can be used as one unit of 3.15 by 1.07 by 0.178 m and inclined up to 30°, or it can be subdivided into up to eight compartments, each with its own drainage filter tubes. The front glass walls allow visual observations of soil packing, wetting fronts, root distribution, etc. The back aluminum walls allow installation of instruments, such as tensiometers, salinity sensors, and psychrome

ISSN:0043-1397    

DOI:10.1029/WR014i004p00611

年代:1978

数据来源: WILEY