Distribution Functions to Represent Center-pivot Water Distribution

Heermann, Dale F.; Duke, Harold R.; Serefim, A. M.; Dawson, L.J.

doi:10.13031/2013.28754

Cited by 25 publications

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“…These functions are affected both by the total amount of water applied and by the non-uniformity of water application across the field. Heermann et al (1991) reported the statistical parameters needed to characterize the effect of uniformity on crop yield. Mantovani et al (1995) simulated the effects of sprinkler uniformity on crop yield by assuming a uniform sprinkler water distribution and a linear crop water production function.…”

Section: Introductionmentioning

confidence: 99%

Predicting alfalfa hay production as related to water distribution functions

Montazar

2008

Irrigation and Drainage

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The present study was carried out to evaluate two crop water production models for estimating the effects of irrigation uniformity on alfalfa hay yields. The models included the ratio of actual to maximum hay yield, two parameters of the sprinkler water uniformity, and the ratio of gross to required irrigation. Measured data from three experimental plots of a farm located in Varamin, Iran, were used for the evaluation of the proposed models. Comparisons showed that the results from both models were in good agreement with experimental results. However, the results obtained from the normal water distribution model were more accurate than those from the uniform water distribution model. The higher predictive accuracy of the normal distribution model may be due to the fact that it follows a normal pattern in terms of irrigation distribution and crop yield. The accuracy of models in estimating alfalfa hay yield improved with an increasing uniformity coefficient. The results indicate that the optimum gross to required irrigation depth ratio decreases with increasing sprinkler water uniformity value. The findings demonstrate the importance of economic constraints in determining the optimum irrigation amount. It was further found that the optimum irrigation depth increased with increasing value of the product to irrigation cost ratio. The results illustrate that normal and uniform models overestimate and underestimate the values of hay yield compared to measured values, respectively. The average difference in the yield estimation compared to measured data was 130 kg ha À1 for the uniform distribution model and 87 kg ha À1 for the normal distribution model. The average alfalfa hay yield over growing period was estimated at 24 400 kg ha À1 for the ranges of CU ch between 80 and 90% in the study region. RÉ SUMÉLa présente étude est menée pour évaluer deux modèles de production irriguée destinés à estimer les effets de l'uniformité de l'irrigation sur les productions de foin de luzerne. Les modèles incluent le ratio entre production réelle et maximum de foin, deux paramètres de l'uniformité d'arrosage par aspersion et du ratio entre irrigation nécessaire et maximum. Les données mesurées sur trois parcelles expérimentales d'une ferme située en Varamin, Iran, ont été utilisées pour l'évaluation des modèles proposés. Les comparaisons ont montré que les résultats des deux modèles sont en accord avec les résultats expérimentaux. Pourtant, les résultats obtenus avec le modèle de distribution normal sont plus exacts que ceux du modèle de distribution uniforme. La meilleure prédiction du modèle de distribution normale peut être due au fait qu'il suit une courbe normale pour la distribution d'eau et le rendement. L'exactitude des modèles dans l'estimation de la production de foin de luzerne augmente avec le coefficient d'uniformité. Les résultats indiquent que le ratio sur le niveau d'irrigation augmente avec l'uniformité. Les conclusions démontrent l'importance des contraintes économiques dans la détermination de la quantit...

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Section: Introductionmentioning

confidence: 99%

Predicting alfalfa hay production as related to water distribution functions

Montazar

2008

Irrigation and Drainage

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“…The probability distribution of irrigation water application has been compared with analytical techniques (Warrick, 1983) and compared to field data (Heermann et al, 1992). Warrick (1983) related the DU lq and CU parameters to application depth coefficient of variation (CV) for the normal, log normal, uniform, specialized power, beta, and gamma probability distributions.…”

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confidence: 99%

“…Warrick (1983) related the DU lq and CU parameters to application depth coefficient of variation (CV) for the normal, log normal, uniform, specialized power, beta, and gamma probability distributions. Heermann et al (1992) surveyed 60 center pivot catch can tests to determine the best statistical distribution among the normal, log normal, uniform, and the specialized power distributions and found the normal distribution fit the measured data better than the other probability distributions. Testing conditions included both spray nozzles and impact sprinklers and tests were conducted in the afternoon, which led to wind speeds as high as 11.5 m/s.…”

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confidence: 99%

Effect of Wind Speed and Pressure on Linear Move Irrigation System Uniformity

Dukes¹

2006

Applied Engineering in Agriculture

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Use of center pivot and linear move sprinkler irrigation systems is becoming popular in the Southeastern United States. As these systems are used to irrigate increasing acreage, quantitative data are needed on sprinkler performance under local conditions. Two types of low pressure sprinkler nozzles were tested under field conditions, stationary grooved plate (LDN) and off-center wobbling diffuser sprinklers (IWOB). Replicated uniformity measurements were conducted along the axis of a linear move irrigation system at low (<1.7 m/s), medium (3.3-3.9 m/s), and high (5.0-6.6 m/s) wind speeds and at two pressure levels of at least 200 kPa, which was in excess of the pressure regulator discharge pressure and less than 97 kPa, a pressure below nominal regulator discharge pressure. Also, the normal probability distribution was investigated to determine how well it represented the sprinkler field data. The IWOB sprinklers coefficient of uniformity (CU) was consistently 10% to 16% higher than the LDN sprinklers over all conditions and ranged from 87% to 93% and 70% to 85%, respectively. The coefficient of uniformity of the LDN sprinklers was significantly improved at higher wind speeds (5.0-6.6 m/s) under low pressure (<97 kPa) operation from 70% to 85%, while other sprinkler/pressure combinations were not affected by wind speed. It was hypothesized that this improvement was due to the formation of larger drops falling in a more random pattern due to inadequate pressure. Finally, the IWOB sprinklers produced a more uniform application of water compared to the LDN sprinklers under all of the testing conditions in this project and the normal distribution adequately represented the field data except for LDN sprinklers at <97 kPa.

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“…Em geral, o aumento da uniformidade de distribuição da água requer investimentos na melhoria do sistema, em manutenção e em mão-de-obra, para o manejo racional da irrigação (Heermann et al, 1992).…”

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Influência Do Espaçamento Entre Aspersores Na Uniformidade De Distribuição De Água Acima E Abaixo Da Superfície Do Solo

Rezende¹,

Frizzone²,

Carlos

et al. 1998

Rev. bras. eng. agríc. ambient.

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A uniformidade de aplicação de água por um sistema de irrigação por aspersão convencional, foi estudada acima e abaixo da superfície do solo. Foram adotados dois espaçamentos entre aspersores e coeficientes estatísticos de uniformidade empregados para a realização de comparações quantitativas. Os resultados obtidos mostram que a redistribuição de água no solo promove uniformidade da umidade do solo maior que a identificada para a lâmina aplicada. O maior espaçamento entre aspersores promoveu menor uniformidade, acima e abaixo da superfície; no entanto, a uniformidade da umidade do solo foi alta o bastante para atender aos critérios usualmente adotados na irrigação por aspersão, ao contrário do identificado acima da superfície. Palavras-chave: irrigação, aspersão, uniformidade de distribuição THE INFLUENCE OF SPRINKLER SPACING ON THE DISTRIBUTION UNIFORMITY OF WATER ABOVE AND BELOW THE SOIL SURFACE ABSTRACTThe application uniformity of water, below and above the soil surface, by a conventional sprinkler irrigation system was studied. Two sprinkler spacings were tested and statistical uniformity coefficients were used to make quantitative comparisons. The results obtained indicated that the redistribution of soil water promotes soil moisture uniformity greater than that identified for the depth of water applied. The larger sprinkler spacing resulted in lower uniformity below and above the soil surface, but soil moisture uniformity remained high enough to meet the usual criterias adopted in sprinkler irrigation, which was not the case above surface. INTRODUÇÃOA irrigação é uma operação agrícola que tem como finalidade básica colocar água à disposição da planta mantendo o solo com umidade adequada utilizando, para isto, diferentes métodos de irrigação.Os diversos sistemas de irrigação têm sido avaliados pela uniformidade da água aplicada na superfície do solo, porém a planta retira água do volume de solo no qual o seu sistema radicular se encontra; portanto, pode-se supor que a uniformidade de distribuição da água no perfil do solo é mais importante que na sua superfície.

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Distribution Functions to Represent Center-pivot Water Distribution

Cited by 25 publications

References 0 publications

Predicting alfalfa hay production as related to water distribution functions

Predicting alfalfa hay production as related to water distribution functions

Effect of Wind Speed and Pressure on Linear Move Irrigation System Uniformity

Influência Do Espaçamento Entre Aspersores Na Uniformidade De Distribuição De Água Acima E Abaixo Da Superfície Do Solo

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