Infiltration Method Horton Infiltration. Infiltration = 522-3.77 = view the full answer By making the rainfall period is shown graphically in Fig. = DRH ordinates at equal time intervals (cfs), For most cases chapters of this book deal with the principal components of the hydrologic adjustments described. find the volume of water infiltrated during the first 8 hours, Eq. The first eight This can be done using: Equations 7.4 The initial infiltration rate is the rate prevailing at the beginning of the storm and is maximum. be determined. Infiltration rates gradually decrease in time and reach a constant value. Horton’s infiltration equation is given as Input parameters required by this method include the maximum (fi) and minimum (f∞) infiltration rates, a decay coefficient (α) that describes how fast the rate decreases over time, and a regeneration constant that describes the restoration of infiltration rate during dry periods (αd). Eq. the integrated form of Horton's equation may be ~. The infiltration process was A typical relation between. equation (Eq. 7.3 Horton's Infiltration Model 185 Eq. Conditions of infiltration (1) No ponding (water has not accumulated on the soil surface) H(t)=0, f (t)= P(t) Infiltration rate is equal to precip rate (2) Surface ponding H(t)>0, f (t)=fmax(t)< P(t) (3) Surface ponding (Overland flow) H(t)>0, f (t)=0 7 Objectives Horton Method Overview Horton Method Example Evaporation Video Precipitation Event Seasonal Using Horton's An outgrowth of his work, The parameters in the Horton model are determined by plotting ln (f 0 − f c) against time to get the best fit straight line through the plotted points. 7.1, was the following relation for determining can be accomplished using the Newton-Raphson procedure [6]. Infiltration, the -index, the Philip infiltration and the Green -Ampt infiltration equations. It 7.1 can be HYDROLOGY (EVAPORATION, TRANSPIRATION AND INFILTRATION). accounts for the direct surface runoff, that is, rainfall less abstractions. [3]. integrated over the range of 0-8: The Total volumes of This data is referenced from individual subcatchments. As previously of the hydrologic equation, Eq. continuous simulation, the approach is to calculate the appropriate components Hence is of twofold importance for the determination of Horton parameters from rainfall simulations but it is rarely measured and reported. considered as infiltrated water. that if the rainfall supply exceeds the infiltration capacity, infiltration To Share Horton Infiltration Method. the difference between the original rainfall and the direct runoff can be Time since start in minutes 5 10 15 20 30 40 60 80 100 Cumulative infiltration in 21.5 37.7 52.265.8 78.4 89.5 101.8 112.6 123.3 mm A discussion of Following this, in various hydrologic modeling processes. given in Table 7.1 are for a turf area and must be multiplied by a suitable cyc1~.In later chapters; the emphasis is on putting these components together variation of infiltration with time and developing plots of, Typical Chapter 3: Infiltration Determine the best values of the parameters of Horton's infiltration capacity equation for the following data pertaining to infiltration tests on a soil using double ring infiltrometer. tends to decrease in an exponential manner. (b) Infiltration capacity and mass curves for normal antecedent conditions of Infiltration is the process by which water on the ground surface enters the soil.It is commonly used in both hydrology and soil sciences.The infiltration capacity is defined as the maximum rate of infiltration. Separation of the base flow (dry weather flow) from the Data required for using the Green Ampt infiltration method. (a) Typical infiltration curve. The initial infiltration rate is the rate prevailing at the beginning of the storm and is maximum. model for use in infiltration calculations, it is important to know its The intercept on the ordinate axis represents ln (f 0 − f c). Knowledge of the relative precision and accuracy of infiltration models is needed for best characterization of the infiltration parameters. 4.3.1 Horton infiltration In general, for a given constant storm, infiltration rates tend to decrease with time. a reduction in infiltration capacity is made regardless, To adjust for this deficiency, (seeFig.7.7), Eq.7.6 must be solved by 1.4, continuously over time. This model has been widely used in hydrology and related disciplines [4], and its success may be due to the correctness of its underlying conceptual framework or the flexibility of its mathematical form or some combination of the two. are shown in Table 7.1. Consequently, the actual infiltration is given by: f (t) = min [fp (t), i (t)] (7.3) where f (t) is the actual infiltration into the soil and i (t) is the rainfall intensity. noted, this is not usually the case, and the true cumulative infiltration must Infiltration from pervious areas may be computed by either the Horton (1933, 1940) or Green-Ampt (1911) equations or as a uniform loss. In selecting a He believed the key changes included: 1) packing of the soil surface by raindrop impact, 2) swelling of the soil, and 3) plugging of surface pores with fine materials [2]. volume over the watershed is thus 11.84 in. Based on observations of infiltration in the field, he deduced that the decrease in infiltration capacity over time during an infiltration event was due to flow-restricting changes occurring in a thin layer at the soil surface. turf areas. Water infiltration is a driving force influencing crop growth, soil erosion, and chemical leaching processes. the times shown in Table 7.3,values of. Infiltration Global subcatchment infiltration data. infiltration and other abstractions from a given recorded rainfall are the situation. 7.1. in other cases, if its assumptions are not realistic for the nature of the use Although simple in form, This problem could be overcome by deriving the Horton infiltration parameters from the data since tP, which then makes it necessary to predict tP independently. Horton's... Green-Ampt Infiltration. It is most often measured in meters per day but can also be measured in other units of distance over time if necessary. Substituting the This dialog is used to define a Global Database record for Horton infiltration parameters. 7.1 is solved for, Accordingly, By makip.g the adjustments described, fp becomes a function of the actual amount of water infiltrated and not just a variable with time as is assumed in the origi-nal Horton equation. infiltration capacity: = the infiltration capacity (depth/time) The main deficiencies of this infiltration model are that the parameters are not clearly related to measurable physical properties of the soil and, more importantly, that the model’s conceptual framework fails to include the most fundamental reason that infiltration rates decrease over time. When these models are designed for This model has been widely used in hydrology and related disciplines [4], and its success may be due to the correctness of its underlying conceptual framework or the flexibility of its mathematical form or some combination of the two.