Search results for "IRRIGATION"

Closed-form solutions of the energy balance equation for drip laterals under the Darcy-Weisbach resistance formula

2018

Many studies have investigated easy methods to design drip laterals, as well as the best resistance equation to use, which is fundamental to accurately account for friction losses. This paper addresses both the features of lateral design relationships and the influence of the friction-loss equation on the design variables. First, simple closed-form solutions of the energy balance equation for both sloped and horizontal drip laterals are derived with the simplified Darcy-Weisbach resistance formula by assuming the Darcy friction factor as invariant versus the Reynolds number. Second, an error analysis is performed assuming the friction factor as constant in the design, which is compared to u…

New Computational Fluid Dynamic Procedure to Estimate Friction and Local Losses in Coextruded Drip Laterals

2007

The design of trickle irrigation systems is crucial to optimize profitability and to warrant high values for the emission uniformity (EU) coefficient. EU depends on variation of the pressure head due to head losses along the lines and elevation changes, as well as the water temperature, and other parameters related to the emitters (manufacturer's coefficient of variation, number of emitters per plants, emitter spacing). Trickle irrigation plants are usually designed using small diameter plastic pipes (polyethylene or polyvinyl chloride). The design problem, therefore, needs to consider head losses along the lines as well as emitter discharge variations due to the manufacturer's variability.…

Closure to “Experimental Analysis of Local Pressure Losses for Microirrigation Laterals” by Giuseppe Provenzano and Domenico Pumo

2006

Assessing a Local Losses Evaluation Procedure for Low-Pressure Lay-Flat Drip Laterals

2014

In the past, several research experiments have focused on the hydraulic characterization of traditional drip irrigation systems, and different design methodologies have been proposed with the aim of achieving very high emitter discharge uniformity (EU). The increasing use of low-pressure lay-flat drip laterals, characterized by a thin-walled polyethylene pipe, makes necessary a specific determination of their hydraulic properties, aimed to a correct design of such systems. Here, the validity of an empirical local losses estimation model was assessed for five different commercial lay-flat drip tapes. Moreover, the errors in the maximum lateral lengths obtained for a fixed emitter uniformity,…

Enhancing TIR Image Resolution via Bayesian Smoothing for IRRISAT Irrigation Management Project

2013

Accurate estimation of physical quantities depends on the availability of High Resolution (HR) observations of the Earth surface. However, due to the unavoidable tradeoff between spatial and time resolution, the acquisition instants of HR data hardly coincides with those required by the estimation algorithms. A possible solution consists in constructing a synthetic HR observation at a given time k by exploiting Low Resolution (LR) and HR data acquired at different instants. In this work we recast this issue as a smoothing problem, thus focusing on cases in which observations acquired both before and after time k are available. The proposed approach is validated on a region of interest for t…

Modelling bulk surface resistance by MODIS data and assessment of MOD16A2 evapotranspiration product in an irrigation district of Southern Italy

2016

Abstract In this study, accurate estimates of daily actual evapotranspiration, ET a , were obtained based on the direct Penman–Monteith application, in which the bulk surface resistance term was computed by considering, as main input, daily remotely sensed Land Surface Temperature (LST). In particular, Eddy Covariance measurements of ET a , associated to LST obtained by MODIS time series (MOD11A2) characterized by 8-day resolution, allowed to calibrate a simple bulk surface resistance model, based on two-years of data observations collected in a quite homogeneous irrigation district of Sicily, where olive grove is the main crop. The model was then validated by an independent database collec…

Impact of climate change and man-made irrigation systems on the transmission risk, long-term trend and seasonality of human and animal fascioliasis i…

2014

Large areas of the province of Punjab, Pakistan are endemic for fascioliasis, resulting in high economic losses due to livestock infection but also affecting humans directly. The prevalence in livestock varies pronouncedly in space and time (1-70%). Climatic factors influencing fascioliasis presence and potential spread were analysed based on data from five mete- orological stations during 1990-2010. Variables such as wet days (Mt), water-budget-based system (Wb-bs) indices and the normalized difference vegetation index (NDVI), were obtained and correlated with geographical distribution, seasonality patterns and the two-decade evolution of fascioliasis in livestock throughout the province. …

Discussion of “Modified Hazen–Williams and Darcy–Weisbach Equations for Friction and Local Head Losses along Irrigation Laterals” by John D. Valiantz…

2007

Using the ARP-03 for high-resolution mapping of calcic horizons

2013

A b s t r a c t. The aim of this work is to present a fast and cheap method for high-resolution mapping of calcic horizons in vineyards based on geoelectrical proximal sensing. The study area, 45 ha located in southern Sicily (Italy), was characterized by an old, partially dismantled marine terrace and soils with a calcic horizon at different depths. The geoelectrical investigation consisted of a survey of the soil electrical resistivity recorded with the Automatic Resistivity Profiling-03 sensor. The electrical resistivity values at three pseudo-depths, 0-50, 0-100 and 0-170 cm, were spatialized by means of ordinary kriging. A principal component analysis of the three electrical resistivit…

Special issue on Trends and challenges of sustainable irrigated agriculture

2014

In the twenty-first century, the shortage of freshwater is one of the most important environmental concerns facing several regions of the world because of the growing demand of increasing population, agricultural intensification, and economic growth. Global climate change will contribute to exacerbate the problem, generating new drought-prone areas and increasing those already characterized by severe aridity. Worldwide it is estimated that, on average, agriculture accounts for 70% of the total water consumption, compared with 10% for domestic consume and the remaining used by industry. Moreover, according to FAO estimates, by 2050 agricultural production has to increase by 60% to satisfy th…