Water Infiltration

Containerized plant production represents an extremely intensive agricultural practice with large amounts of moisture and fertilizer application. Hydro-physical characteristics such as water infiltration, texture and structure, particle size distribution affect the quality of the media used in containerized agricultural systems and the water availability to plants. Water retention characteristics depend on particle size distribution as well as the composition of the media used. Materials with coarser particles allow faster percolation of water and also retain relatively higher amounts moisture per unit weight due to higher porosity, while draining faster due to smaller surface area per unit weight. Faster drainage can result into airflow through coarser materials causing the media to dry. The objectives of this study were to characterize the selected hydro-physical properties of plant growth media that are commonly used by nurseries in South Florida. Characterization of the plant growing media can allow modeling of soil-water interactions and development of best management practices for more efficient use of water and agrochemicals by nurseries. Experimental analyses were performed to characterize the plant growth mixtures in terms of particle size distribution and hydraulic conductivity using three different methods (i.e., constant head permeability, falling head permeability test, and tension infiltrometer test). The saturated hydraulic conductivity of the mixtures measured by constant head method ranged from 0.029 to 0.042 cm/s (104-151 cm/h) and by falling head method ranged from 0.078 to 0.112 cm/s (281-403 cm/h). The saturated hydraulic conductivity of the mixtures measured by tension infiltrometer ranged from 0.02 to 0.34 cm/h. Understanding water retention and permeation characteristics of the plant growing media could assist development of best management practices (BMP) for containerized agricultural systems for efficient management of irrigation water and agrochemical use.

This paper presents the physical basis of the FRACTURE submodel for simulating infiltration of precipitation/irrigation water into relatively dry, cracked, fine-textured soils. The FRACTURE submodel forms part of the HYDRUS-ET variably saturated flow/transport model. Infiltration into the soil matrix is formally divided into two components: (1) Vertical infiltration through the soil surface; and (2) lateral infiltration via soil cracks. The first component is described and solved using the 1D Richards' equation. Excess water that does not infiltrate through the soil surface is either considered to be runoff, if no soil cracks are present, or routed into soil cracks from where it may laterally infiltrate into the soil matrix. Horizontal infiltration from soil cracks into the soil matrix is calculated using the Green-Ampt approach and incorporated as a positive source/sink term S f in the Richards' equation describing flow in the matrix. In addition to the hydraulic properties of the soil matrix, the FRACTURE submodel requires parameters characterizing the soil cracks, notably the specific crack length per surface area l c and the relationship between crack porosity P c and the gravimetric soil water content w. An example problem shows that infiltration from soil cracks can be an important process affecting the soil water regime of cracked soils. A comparison with the more traditional approach, involving surface infiltration only, indicates important differences in the soil water content distribution during a rainfall/irrigation event. This extension of the classical approach to include crack infiltration significantly improves the identification and prediction of the soil water regime.

A phenomenon called 'piping' often occurs in hydraulics works, involving the formation and evolution of a continuous tunnel between the upstream and the downstream sides. The hole erosion test is commonly used to quantify the rate of piping erosion. However, few attempts have been made to model these tests. From the equations for diphasic flow with diffusion, and the equations of jump with erosion, a piping model is developed. A characteristic time of internal erosion process is proposed. Comparison with experimental data validates our results. To cite this article: S.

Field properties-topography, hydraulic resistance, and infiltration-play an important role in the performance of surface irrigation systems, and appropriate characterizations of these are required as data input to simulation or design software. The EWRIIASCE Task Committee on Soil and Crop Hydraulic Properties has been charged with preparing a guide for practitioners faced with such data entry. The result is this special section of the Journal of Irrigation and Drainage Engineering in which this paper is the first in the series presented. It describes the characteristics of these field properties and notes a series of caveats to be considered when dealing with them in the course of analyses or designs of surface irrigation systems.

The U.S. Environmental Protection Agency and a group of collaborators from academia, industry, and the regulatory community are conducting research to determine whether landfill covers that use fine soils and vegetation to keep moisture from persolating into landfills can compete favorably at some locations with more conventional clay and composite covers.

A laboratory experiment was performed to assess the impact of ecologically different earthworm species on soil water characteristics, such as soil tension, water content, and water infiltration rate. Three earthworm species (Lumbricus rubellus, Aporrectodea caliginosa, Lumbricus terrestris) were exposed in soil columns (diameter 30 cm, height 50 cm) for 100 days with a total fresh earthworm biomass of 22.7 AE 0.4 g per column, each in duplicate. Each column was equipped with tensiometers at 10 and 40 cm and FD-probes at 10 cm depth, to continuously measure the temporal development of soil tension and soil moisture. Additionally, 30 g of sieved and rewetted horse manure was placed on the soil surface as a food source. Precipitation events (10 mm) were simulated at day 28 and day 64. At the end of the experiment the water infiltration rate and the runoff at 55 cm depth were determined. The results showed considerable evidence, that ecologically different earthworms modify soil water characteristics in different ways. The anecic L. terrestris and the endogeic A. caliginosa showed the tendency to enhance the drying of the topsoil and subsoil. Their intensive and deep burrowing activity might enhance the exchange of water vapor due to a better aeration in soil. In contrast, the epigeic L. rubellus tended to enhance the storage of soil moisture in the topsoil, which might be linked to lower rates of litter loss from soil surface and thus a thicker litter layer remaining. A. caliginosa led to considerable higher water infiltration rates and faster water discharges in the subsoil, relative to the other species, probably due to a high soil dwelling activity.

ChlorophyUlevel in leaf discs of Datura stramonium declined sharply after excision, whilst discs ,hich were infiltrated with distilled water maintained their chlorophyll content at the initial level ven after 10 d of incubation. Etluel, a potent promoter of senescence, had no effect on the chloro-,hyillevel of the discs infiltrated with distilled water. However, the protein content of control as well s infiltrated leaf discs decHned at about the same rate. It is concluded that chlorophyll degradation, widely accepted parameter offoliar senescence, may not be an inevita.ble part of aging phenomenon, nd chlorophyll and protein breakdown Me not inter·related processes.

This paper presents the physical basis of the FRACTURE submodel for simulating infiltration of precipitation/irrigation water into relatively dry, cracked, fine-textured soils. The FRACTURE submodel forms part of the HYDRUS-ET variably saturated flow/transport model. Infiltration into the soil matrix is formally divided into two components: (1) Vertical infiltration through the soil surface; and (2) lateral infiltration via soil cracks. The first component is described and solved using the 1D Richards' equation. Excess water that does not infiltrate through the soil surface is either considered to be runoff, if no soil cracks are present, or routed into soil cracks from where it may laterally infiltrate into the soil matrix. Horizontal infiltration from soil cracks into the soil matrix is calculated using the Green-Ampt approach and incorporated as a positive source/sink term S f in the Richards' equation describing flow in the matrix. In addition to the hydraulic properties of the soil matrix, the FRACTURE submodel requires parameters characterizing the soil cracks, notably the specific crack length per surface area l c and the relationship between crack porosity P c and the gravimetric soil water content w. An example problem shows that infiltration from soil cracks can be an important process affecting the soil water regime of cracked soils. A comparison with the more traditional approach, involving surface infiltration only, indicates important differences in the soil water content distribution during a rainfall/irrigation event. This extension of the classical approach to include crack infiltration significantly improves the identification and prediction of the soil water regime.

Current methods to determine unsaturated soil properties are exringe pump to maintain the Bruce-Klute inlet boundary pensive, difficult, and time-consuming. A procedure is presented that condition. An improved data analysis procedure is also quickly estimates the unsaturated hydraulic conductivity, diffusivity, water retention, and sorptivity functions from a Bruce-Klute test in presented, which permits independent optimization of conjunction with a semi-analytic analysis. Data collection was pervan Genuchten soil hydraulic parameters n and ␣. Addiformed using a computer controlled ␥-ray attenuation system to meationally, the procedure optimizes an additional paramesure moisture content. A computer controlled syringe pump mainter, residual moisture content, from a single measuretained the inlet boundary conditions. Improvements to existing ment of water potential versus water content. analytical procedures include the independent optimization of van Genuchten soil hydraulic parameters n and ␣, and a method to optimize the residual moisture content from a single measurement of THEORY water potential versus water content. The method was applied to a Van Genuchten Parameters sandy loam and its strengths and weaknesses are discussed. This method uses van Genuchten's expression for water retention (van Genuchten, 1980), although similar versions K nowledge of soil hydraulic properties is required utilizing Brooks and Corey (Brooks and Corey, 1966) or nuto estimate fluid flow in unsaturated porous media. merous other versions could be used. Van Genuchten de-Commonly, numerical models are employed to estimate scribes the water retention curve by View publication stats View publication stats

Through action research and development partnerships, Africa RISING is creating opportunities for smallholder farm households to move out of hunger and poverty through sustainably intensified farming systems that improve food, nutrition, and income security, particularly for women and children, and conserve or enhance the natural resource base.

Geographic Information System (GIS) software was used to create a watershed vulnerability model for Bernalillo County, New Mexico. Watershed vulnerability was investigated as a function of soil erosion and infiltration criteria: precipitation, land slope, soil erodibility (K-factor), vegetation cover (NDVI), land use, drainage density, saturated hydraulic conductivity, and hydrologic soil group. Respective criteria weights were derived using a Fuzzy Analytic Hierarchy Process (FAHP) supported by expert opinion. A survey of 10 experts, representing New Mexico Institute of Mining and Technology (NMT), the New Mexico Bureau of Geology and Mineral Resources (NMBGMR), and the United States Geologic Survey (USGS), provided model input data for an integrated pair-wise comparison matrix for soil erosion and for infiltration. Individual criteria weights were determined by decomposing the respective fuzzy synthetic extent matrix using the centroid method. GIS layers were then combined based on criteria weights to produce maps of soil erosion potential and infiltration potential. A composite watershed vulnerability map was generated by equal weighting of each input map. Model results were categorized into five vulnerability categories: not vulnerable (N), slightly vulnerable (SV), moderately vulnerable (MV), highly vulnerable (HV), and extremely vulnerable (EV). The resulting FAHP/GIS model was used to generate a watershed vulnerability map of discrete areas in Bernalillo County, which may be vulnerable to stormwater runoff events and soil erosion. Such high volume runoff events can cause erosion damage to property and infrastructure.

The methods of estimation of soil-crack characteristics and the possible in¯uence of soil cracks on the in®ltration are described in this article. The most important properties of soil cracks, namely volume of cracks, internal crack surface and soil-crack depth were estimated using easily measured soil characteristics: the speci®c length of cracks on a soil surface,crack porosity on a soil surface, soil water-content pro®les and laboratory estimated relationships between crack porosity and mass soil-water content. Presented methods of soil-crack characteristics estimation were applied on two heavy soils in the NOPEX area, near Uppsala, Sweden. A total volume of soil cracks per unit surface area estimated under current conditions in the ®eld was 27 mm of water (Lo Ívsta, CFE 1 , soil covered by rye canopy) and 6.2 mm water layer in Marsta, CFE 2, under spring barley canopy. Internal crack surface area was found up to 2.7 times higher than topographic soil surface area (Lo Ívsta) and 13 times higher in the Marsta site under given conditions. Results obtained illustrate possible importance of crack formation on soil-water regime. Characteristics of soil cracks mentioned are a part of input data of mathematical models of in®ltration into soil with cracks.

The paper is devoted to nonlinear observer and control design for irrigation canals or dam-river systems. Such systems are known to be described by non-linear partial differential equations (Saint-Venant equations). Here, a finite-dimensional model, previously developed by collocation methods and used for control design, is now further used for flow rate and water infiltration observation. In particular, it is pointed out how the obtained estimates can successfully be used in the previously designed state feedback controller, resulting in a water level control law only using three level measurements along the canal. The results are illustrated in simulation, both on the considered simplified model and on more realistic representations of water flow dynamics.

Shrubs have invaded extensive areas of grassland in the southwestern United States. The zones of nutri-ent-rich soil found beneath plant canopies, referred to as “islands of fertility,” are more intense and spaced farther apart in shrubland than in grassland. This ...

The objectives of this study were to develop an equation for the ponding time, t p , and determine the number of on-off cycles using the infiltration equations introduced by Horton and Kostiakov and to compare the observed and predicted ponding times t p. To achieve these objectives, a sprinkler infiltration test was conducted on the Harran soil series at the Sanhurfa-Koruklu, Tubitak Agricultural Research and Development Station on the Harran plain. The soil characteristic parameters of the Horton and Kostiakov equations were determined from the results of sprinkler infiltration tests. The ponding time equations were developed by choosing a sprinkler application rate of i s = 13.61 mm h À1 that is higher than the steady-state infiltrability rate of i ss = 7.1 mm h À1. The number of on-off cycles was then determined from repeated cycles. The ponding times t p for the experiment, the Horton equation, and the Kostiakov equation were 4.17, 4.09 and 2.69 h, respectively. The numbers of on-off cycles for all three methods were estimated to be two. Under the same management conditions, it was concluded that irrigation at a rate i s > i ss could be completed in 44% less time without the occurrence of runoff and erosion.