Journal of Irrigation and Drainage Engineering

Quantification of soil moisture content is important for understanding physical processes that occur on and within the earth. The methods that are currently used for the determination of soil moisture content are point-based (gravimetry, time-domain reflectometry, neutron scattering, or gamma ray scanning). Remote sensing methods exist but have several disadvantages (poor resolution and dependence on local meteorological conditions). The objective of the study described herein was to determine soil moisture content by means of remote sensing from hyperspectral imagery. Reflectance values obtained from optical remote sensing (wavelengths from 350 nm to 2,500 nm) were acquired from materials with different moisture content levels. Reflectance values, obtained from a spectroradiometer, were obtained for three soils and two commercial sands and then correlated with the initial soil moisture content obtained from gravimetric methods. The correlations were based on the collected reflectance values at prescribed wavelengths and a continuum analysis across all wavelengths. For all investigated materials, the reflectance values decreased with increasing moisture content. The best results were obtained when 1,900 nm was considered (coefficients of determination greater than 0.94, indices of agreement greater than 0.97, coefficients of efficiency greater than 0.41, mean absolute error less than 1.2 percent, and root mean square error less than 1.6 percent). With the continuum analysis, 1,450 nm was the best wavelength. Based on these results, a correlation was observed to exist between soil moisture content and the spectral reflectance values. Using this technique, the determination of soil moisture content can be rapidly obtained (within seconds).

Abstract

Despite recent advances in leak detection in water supply systems, previous studies focused mainly on material aspects or orifice opening characteristics. This study evaluated geometric, hydraulic, and hydrodynamic factors influencing on water leaks using three-dimensional (3D) computational fluid dynamics (CFD) simulations. The simulated discharge coefficient ($C_d$) had a maximum absolute deviation of 8% compared with experimental data. The results indicated that the variation of $C_d$ as a function of the diameter and orifice size can be attributed to the effect of tube curvature on flow convergence through the orifice. The statistical analysis concluded that the orifice-to-pipe diameter ratio $d/D$ is the best dimensionless parameter that explains this phenomenon, which agreed with the analyses of the streamlines and turbulent eddy dissipation rate in the simulations. Other important dimensionless parameter are the ratio of the pressure head differential at the orifice to the pipe diameter $\mathrm{\Delta }H/D$, Reynolds number (R), and the ratio of the pressure head differential at the orifice to the wall thickness $\mathrm{\Delta }H/e$, in order of relevance. A set of empirical correlations was elaborated through a nonlinear multiple regression analysis with Reynolds numbers ranging between 12,000 and 52,000, and pressure head differential ranging from 1 to 45 m. This study advances the knowledge of cross-flows through orifices, and the proposed correlations potentially can improve the prediction of water leaks in pipes.

Practical Applications

This study demonstrates the applicability of computational fluid dynamics simulations for understanding the leakage phenomenon in pipes, and obtained a set of empirical correlations that potentially can improve the prediction of leakages in water distribution systems. The authors propose an equation for estimating the discharge coefficient in practical applications. This equation balances the number of terms (three dimensionless coefficients) and accuracy ($R^2=98\%$). Although it is dimensionless, the correlation must be used within the established ranges of values to ensure its effectiveness: Reynolds numbers from 12,000 to 52,000, and pressure head differentials from 1 to 45 m.

Proper filtration selection, sizing, maintenance, and performance of a filtration system are crucial for removing suspended solids in water, preventing clogging of emitters, and ensuring a high-performing microirrigation system throughout its lifespan. Filtration prevents the intake of particles larger than the pore size specified in a given filtration grade. Proper selection of the filter media ensures efficient solid–liquid separation. Strainer-type or screen filters have elements composed of a woven or nonwoven cloth of numerous weave types. The material and characteristics of the screen directly affect the fluid flow and filter performance. The aim of this study is to propose a method for determining the actual filtration grade of filters used for irrigation. An automatic flushing strainer-type filter was equipped with five filter element models, composed of woven and nonwoven materials, for evaluation. A new methodology was developed to assess the actual filtration grade based on the removal efficiency for suspended solids under controlled and repeatable conditions. The removal efficiency of each filter element was determined for particle size ranges defined according to the filtration grade declared by the manufacturer. The proposed methodology allowed for the assessment of the actual filtration grade of each model of filter element operated with water containing suspended particles of silica sand. The filtration grade declared by the manufacturer was confirmed for some of the filter elements, but it could be modified for others. The proposed methodology could be useful for assessing the actual filtration grades of screen, disk, and media filters.