Ponding Time Research Articles

Testing of Approximate Expressions for Soil Water Status at the Surface During Infiltration

Approximate expressions for the water content at the soil surface during constant flux infiltration and for the time to ponding under a range of constant surface fluxes are tested using a well‐established computer‐based numerical approach which has recently been validated against exact analytical solutions. The expression for the surface water content shows agreement to within 1% over the entire time range simulated. For the time to ponding case, it is found that a geometric mean of the data from equations defining coarse upper and lower bounds of ponding time provides an easy and accurate estimate of the ponding time.

A numerical study of infiltration through crusted soils: Flat and other surface configurations

A finite-difference numerical solution of Richards' infiltration equation is developed for one and two-dimensional vertical flow. The model is first validated against experimental observations obtained on a vertical sand column. A comparison between two ways of modelling the crust is presented. In the first approach the crust is assumed to be instantaneously saturated and has an impedance characterized by a hydraulic resistance. The alternative method considers the crust and the underlying soil as a two-layered system. The two methods give almost the same infiltration flux with the only difference that ponding time is shorter for the impedance model since no water is needed to saturate the crust. Also the numerical model is applied to crusted furrow to compare the solution given by a two-dimensional method with one obtained by a one-dimensional approach. It is found that topographic form of the surface at this small scale is not an important parameter.

Space Solution of Kinematic‐Wave Model by Time Iteration

A kinematic-wave model was developed to solve for time to advance to specified locations along the furrow where infiltration was measured as a function of ponding time and wetted perimeter. Time step increased during advance to take advantage of the more slowly changing flow profile. In an earlier model developed by Rayej and Wallender, the system of nonlinear flow equations was solved implicitly for flow area and time step using the double-sweep technique. Coding requirements were extensive and computation time was protracted, however. Performance of the time-iteration model was compared with the double-sweep model. Advance trajectories for both uniform and nonuniform soils are essentially the same for both time-iteration and double-sweep methods. For both models, advance time decreases as space step decreases for both soil types. Computation time for the time-iteration model is one-third and one-fourth of the computation time for the double-sweep model for uniform and nonuniform soil, respectively. As e...

Infiltration rates and erosion associated with reclaimed coal mine spoils in west central New Mexico

Large quantities of coal are extracted in New Mexico by surface mining that results in large areas of surface disturbance. Some goals of reclaiming these disturbances are to control erosion and consequent sediment yields by recontouring and revegetation. This study investigates the rates of infiltration and sediment removal on successfully reclaimed coal mine areas, and their relationship with analogous undisturbed rangeland. Reclaimed areas that had been revegetated for one, three and five years, and a nearby natural rangeland, were subjected to simulated rainfall. Ponding time and runoff time were similar between the non-disturbed lands and the areas reclaimed one and five years before for both dry and wet soil moisture scenarios. The area revegetated three years before required substantially longer time to pond and yield runoff than the rangeland. The reclaimed areas with three and five growing seasons displayed greater infiltration rates than the rangeland area on dry soils and wet soils. Infiltration rates for the reclaimed area with one growing season were similar to the natural rangeland area for both soil moisture conditions. Sediment production and concentrations on the newly reclaimed areas were equal to, or greater than, that for the rangeland on dry and wet soils, respectively. The reclaimed area with the most established vegetation yielded the least sediment of all the reclaimed sites, and significantly less than the rangeland site, regardless of soil moisture situations. Various vegetation, rock, soil, and surface roughness variables were found to influence ponding and runoff times, infiltration rates, sediment production, and sediment concentration. These variables include, in decreasing importance: foliar grass cover, grass production, bulk density, foliar shrub cover, shrub production, horizontal roughness, litter cover, vertical roughness, rock cover and organic matter content.

Reply to “Comments on ‘Upper and Lower Bounds of the Ponding Time for Near Constant Surface Flux’”

Reply to “Comments on ‘Upper and Lower Bounds of the Ponding Time for Near Constant Surface Flux’”

Comments on Upper and Lower Bounds of the Ponding Time for Near‐Constant Surface Flux

Comments on Upper and Lower Bounds of the Ponding Time for Near‐Constant Surface Flux

Upper and Lower Bounds of the Ponding Time for Near Constant Surface Flux

AbstractUpper and lower bounds on the relation between the time course of cumulated infiltration into soil and water content at the soil surface are derived. These estimates can be used specifically to predict upper and lower bounds of the ponding time. The analytical results are derived for mildly varying surface flux. However, the accuracy of the limits is illustrated and discussed for Granoble sand with constant rainfall rates only. A numerical solution is also obtained that yields results outside the range of the more accurate analytical results. This confirms that errors are introduced in the numerical scheme during the early stages of infiltration. Less accurate, but easier to apply, analytical limits are also presented and discussed.

Water Ponding on Level Basins Caused by Precipitation

LEVEL basins, areas of any configuration with no slope and surrounded by a control dike, pro­ vide a unique land shape within which water from both irrigation and precipitation can be uniformly distributed on cropped fields and within or from which no erosion will occur. Excess water retained on level basins, however, can interfere with crop production. The hydrology component of the CREAMS model was modified to estimate ponding (inundation) events on level basins for any region with or without irrigation. Ponding was assessed by looking at the duration of inundation events (ponding time) on a monthly basis for various return periods. Differing precipitation amounts and patterns were studied by using weather data from three climatically different regions represented by Phoenix, AZ; North Platte, NE; and Columbia, MO. As monthly rainfall increased, expected ponding time also increased. For the *'worst case situation studied (Columbia in June), the ponding time would exceed 10 h every 10 years only when the final infiltration rate was less than about 2.5 mm/h. As final infiltration rates increased beyond 2.5 mm/h, the expected ponding times decreased rapidly to durations of less than 5 h. Irrigating tended to increase the ponding time expected from rainfall events (due to the likelihood of rainfall following an irrigation).

PORE-SIZE DISTRIBUTIONS AND INFILTRATION

This paper presents a quantitative assessment of the dependence of infiltration rate on changes in pore-size distribution of soils. It summarizes concepts of pore-size distribution, displacement pressure head, and relative permeability in the context of a capillary model of soil. These concepts are then applied to the Green-Ampt equation and to infiltration equations that account for flow of the gas phase developed by McWhorter (1971), Morel-Seytoux and Khanji (1976), and Morel-Seytoux (1974). The Green-Ampt equation and the analogous two-phase flow equation are compared. Effects of changes in pore-size distribution on infiltration rates into a semiinfinite soil under a constant depth of ponding, ponding times for a semi-infinite soil subject to a constant liquid flux boundary condition, and ponding times for a soil subject to a constant liquid flux and equal, but opposite, air counterflow boundary condition are discussed.

Experimental and numerical analysis of two-phase infiltration in a partially saturated soil

The purpose of this study is to analyze the effects of the soil air flow on the process of water infiltration in a 93.5 cm deep vertical column for varied boundary conditions at the surface - positive time constant head; time constant fluxes smaller and greater than saturated soil hydraulic conductivity. Several experiments conducted on a sandy soil column with and without a possible air flow through the wall are presented. Continuous and simultaneous measurements of water content and air and water pressure heads at different depths allow the analysis of the air and water movements within the soil and the determination of the capillary pressure and relative permeability for each phase as functions of the volumetric water content. A numerical solution of the equations describing the simultaneous flow of air and water is compared with the experimental data and with the traditional one-phase flow modeling. The results show that the air movement may significantly affect water flow variables such as infiltration rates, water content profiles, and ponding times. Furthermore, some basic assumptions used in two-phase flow modeling, such as the hydrodynamic stability of the wetting fronts and the pertinence of the relative permeability concept, are discussed in the light of the experimental data.

A Two‐Phase Numerical Model for Prediction of Infiltration: Case of an Impervious Bottom

A numerical procedure to describe soil moisture evolution in a column with an impervious bottom for varied boundary conditions at the soil surface is presented. The procedure accounts for viscous resistance to simultaneous flow of water and air and for air compression. The method was programmed for the computer. In one case study a 10‐cm‐deep soil column is subjected to a steady rainfall at the surface. Moisture profiles and infiltration rates are calculated by both the one‐ and two‐phase approaches. Comparison demonstrates the magnitude of the error incurred when air effects are not incorporated in the analysis. In a second case study a 100‐cm‐deep soil column is subjected to a sequence of two different rainfall rates. Again comparison of results by the two approaches (traditional versus two phase) provides a measure of the error resulting from the neglect of air effects in the analysis. Not only is capacity infiltration rate greatly reduced after ponding of soil surface but the ponding times themselves are greatly reduced due to increased viscous resistance to flow when airflow is considered in the analysis. The more rigorous analysis complicates little the basic numerical procedures and performs the calculations at essentially no extra cost.

Summer Arctic sea ice character from satellite microwave data

In situ microwave data for the microscale properties of sea ice are combined with satellite data on the macroscale properties to construct an interpretation method for satellite data on sea ice for the warm season. Scatterometer, or calibrated radar, data give information on ice surface conditions, and radiometer data give information on areal concentrations of ponds and leads. The pond data are determined by examining fractional areas of exposed ice and using parameterized lead areas. These results are used to develop diffuse‐illumination surface albedo estimates for the time of maximum ponding, near day 195, and that of minimum ice cover, near day 258. The estimated ponding albedos range from 0.5 to 0.6, and ice cover minimum albedos range from 0.6 to 0.8. During summer, the 37‐GHz radiometer data are nearly independent of sea ice properties and are dominated by atmospheric and snow cover conditions. Lower‐frequency data are increasingly useful for interpreting ice conditions. Substantial anisotropy in backscatter is recorded in scatterometer data at 14 GHz, with surface resolution of 50 km showing 90° anisotropy in the 0.5–1 dB range. In Nimbus 5 and Seasat data, some variation in satellite‐recorded microwave properties during the period between 195 and 258 cannot be directly interpreted but are thought to be due to weather.

Initial Egg Weight, Time to Maximum Alevin Wet Weight, and Optimal Ponding Times for Chinook Salmon (Oncorhynchus tshawytscha)

Eggs of chinook salmon (Oncorhynchus tshawytscha) were segregated into eight size groups (range 163–437 mg) and incubated at 5, 7.5, 10, and 12.5 °C. The time required to reach maximum alevin wet weight (MAWW) varied significantly (p < 0.01) both with mean incubation temperature (T °C) and with initial egg weight (W mg). A good (R2 = 98.4%, n = 21) prediction of days postfertilization to MAWW (D) is given by[Formula: see text]Optimal ponding times are closely associated with the attainment of MAWW and can be estimated using this equation. Data relating mean incubation temperatures (T) to actual ponding time were collected from 17 hatcheries throughout British Columbia. The equation[Formula: see text]where D′ is days postfertilization to ponding, provided the best fit to the data (R2 = 97.5%, n = 85). Hatchery ponding times were not significantly different from times to MAWW predicted for 200-mg eggs.

Infiltration in Swelling Soils

Infiltration phenomena in swelling soils were investigated theoretically. The approach taken consisted of applying both the approximate analytical techniques developed by J.‐Y. Parlange and co‐workers and conventional finite difference numerical methods to study the generalized Richards equation for one‐dimensional infiltration in a swelling soil. Equations were derived for the ponding time and the post‐ponding infiltration rate that are generalizations of the Parlange‐Smith model expressions for rigid soils. Ponding times for swelling soils were shown to be shorter than those for nonswelling analogs, and post‐ponding infiltration rates in swelling soils were shown to approach zero instead of becoming equal to the hydraulic conductivity, as in rigid soils. These results were confirmed, both qualitatively and quantitatively, with the numerical model, which also provided instantaneous moisture profiles and surface swelling predictions in agreement with field observations. A three‐parameter infiltration equation proposed recently by J.‐Y. Parlange et al. (1982) was generalized to describe swelling soils and shown to be in good agreement with published laboratory and field data. It appears that the generalized analytical model equations developed can be employed conveniently in hydrologic applications which do not require high accuracy in predictions.

Scanning Electron Microscope Studies of Surface Crusts Formed by Simulated Rainfall

AbstractThe micromorphology of the surface layer of three California soils, Columbia fine sandy loam, Wyo clay loam, and Yolo silt loam, undergoing crust formation by simulated rainfall was studied using the scanning electron microscope (SEM). Crusts formed at the time of ponding (early crust) and after 60 min rainfall were examined. At the early crust stage, crusts on all soils comprised a very thin compact surficial layer, about 0.05 mm thick, and a more open underlying layer of uniform pore and particle size distributions comparable to those of the undisturbed soil. At a later stage, the crusts on Yolo and Wyo soils consisted of an upper layer (about 0.1 mm thick) of high porosity, composed predominantly of individual sand grains and a lower layer of considerably reduced porosity, composed of a higher concentration of clay and silt sized particles. The lower layer, called the “washed‐in” zone, results from the accumulation of fine materials washed out in the upper layer. Columbia late crust also comprised an upper compact surface layer (about 0.05 mm thick) of well oriented platy particles, and a lower more open layer with particles uniformly reduced in size. Decreased apparent porosity at 0.3‐ to 0.8‐mm depth, measured directly on the SEM photomontages, indicated the presence of the “washed‐in” zone in the Yolo and Wyo late crusts and its absence in the Columbia. Mean pore size of the late crust Yolo sample was significantly reduced compared to the no‐crust treatment. Small changes in mean pore size were also observed for the other two soils.

Assessing the Suitability of Soils With Macropores for Subsurface Liquid Waste Disposal

AbstractThe capacity of soils to accept and purify liquid waste can be manipulated by using different application regimes. The associated transient soil physical conditions, which govern purification processes, were measured experimentally in soil columns and in situ, and were predicted by simulation in three soils of which two had macropores.Measurements of pressure heads, outflow rates, and breakthrough curves were made following intermittent liquid applications of 2 cm d−1. Rapid breakthrough and short‐circuiting, which were observed in the soils with the macropores, could be reduced by adding a light crust.Predictions involved computer simulation of pressure heads during infiltration and redistribution, and of outflow rates in the columns. Good agreement was found between measured and calculated values, but only when the model for soils with macropores was modified to include a subprogram for macropore flow. Simulation required hydraulic conductivity (K) at and near saturation, which was obtained with a modified crust test procedure.Use of the simulation program allows the prediction of soil physical conditions for a range of application rates in terms of ponding times and drainage rates, which affect purification and clogging. Measurement of breakthrough curves yields travel times as a function of application rates. Optimal application rates can be estimated by considering these two types of data, as is illustrated with an example. This approach is preferred over the current procedure using a single hydraulic parameter.

Calculation of Sorptivity from Constant‐Rate Rainfall Infiltration Measurement

AbstractThe incipient ponding time equation developed by Kutilek and Parlange and Smith were rearranged and used for calculating sorptivity under constant‐rate rainfall conditions. The equations were tested using the field‐measured data obtained in Hawaii by Dangler et al. In the calculation, the incipient ponding time is assumed equal to the time of first appearance of runoff from the experimental plot. Additionally, the A value in the Philip two‐term infiltration equation is assumed to the Ksat/3. The results showed that the sorptivity values calculated from both equations have only a 1.22% difference. The accuracy of the calculated sorptivity was assessed by its use for predicting infiltration. In the comparison of cumulative infiltration, the correlation coefficient between measured and estimated values is > 0.9 with a mean error percentage of 20.09 and a median of 10.57%.

Water Infiltration and Redistribution in a Silt Loam Subsoil with Vertical Worm Channels

AbstractInfiltration and redistribution of water in a fine silty, mixed, mesic Fluventic Eutrochrept with macropores (dominantly vertical worm channels) were studied with physical and morphological techniques. Infiltration rates in individual worm channels were measured and channel morphology was studied by excavation after adding methylene blue and gypsum. Three different steady infiltration rates corresponded with different channel morphology. One channel occurred per 200 cm2 of soil. The measured, dominant infiltration rate in a channel was used to calculate ponding time on and the associated water movement in the soil matrix after adding 2 cm of water. The latter was calculated with an existing simulation model for one‐dimensional infiltration in homogeneous soil using K‐θ and h‐θ data. Calculations of h indicated lack of soil saturation. This agreed only with in‐situ measurements when small tensiometer cups were used. Large cups intercepted water‐conducting macropores, erroneously suggesting saturation of the entire soil matrix. Addition of a 5‐cm thick layer of sand to the surface of infiltration made the macropores discontinuous and induced saturated conditions, as measured and simulated. Measurement of infiltration rates into individual macropores, rather than calculation of those rates, is recommended when macropore morphology is irregular.

An approximate integral solution of vertical infiltration under changing boundary conditions

An approximate solution of the Richards equation was obtained with a spectral series solution for rain infiltration under changing boundary conditions. Prior to surface ponding a flux boundary condition was employed, which was followed by a concentration boundary condition. During this latter stage a flux matching boundary condition was used to describe the movement of the interface between the saturated and unsaturated zones. The solutions yield a general expression for ponding time, wetting front advance, and soil water profile. Infiltration rates beyond ponding include the effect of time dependent ponding height and saturation depth.

APPLICATION OF INFILTRATION THEORY FOR THE DETERMINATION OF EXCESS RAINFALL HYETOGRAPH1

ABSTRACT: The purpose of this paper is to show through the use of numerical examples that modern infiltration theory can be used in everyday hydrologic practice. The actual use of four methods of calculation of infiltration rates and of excess rainfall rates is demonstrated for the case when simultaneous data of rainfall and stream flow are available for a watershed. The four methods are: (1) the well known Π‐index method, (2) the traditional Horton's infiltration capacity formula, (3) the less traditional Green and Ampt infiltration capacity formula, and (4) a ponding time approach. It is recommended that hydrologists become at least familiar with the numerical procedures involved in the ponding time and postponding infiltration approach. This approach, though not flawless, should be preferred to the other three methods if use of the other three is at all considered.