Test methods for characterising the water distribution from irrigation sprinklers: Design, evaluation and uncertainty analysis of an automated system

Koech, RK ORCiD: 0000-0002-0563-6687An automated system for indoor testing of irrigation sprinklers was developed and evaluated. The system was designed to test single sprinklers with jet lengths up to 18 m. The tests involve the use of 36 collectors (catch-cans) spaced at 0.5 m intervals along the jet radius. A single pressure transducer coupled to a manifold equipped with solenoid valves was employed to sequentially scan the water level in each collector. Radial application rates were determined based on water level measurements. Results obtained using the automated system were compared with those obtained using manual operation using mass measurements. Uncertainty analysis of the manual method was compared with the automated system. The automated system was found to be as reliable as the manually operated system for testing sprinklers. Although minor differences in the application rates measured by the two methods were detected, they did not cause appreciable differences in the distribution uniformity indicators used. The results presented will provide useful baseline for uncertainty analysis in irrigation sprinkler testing

Minor losses in start connectors of microirrigation laterals

Abstract Fittings called start connectors are usually employed to attach each lateral to its corresponding manifold in microirrigation systems. The protrusion of start connectors’ barbs into the manifold induces pressure losses due to contraction and subsequent enlargement of streamlines. In addition, when water flows from a manifold toward a lateral through a start connector, a sudden contraction followed by expansions of flow streamlines cause pressure loss whose intensity is influenced by connector’s geometry. Minor losses along manifolds or at laterals inlet due to start connectors may be significant and might be considered on subunits design or while undertaking hydraulic simulations. The objectives of this research were: (a) to develop equations based on dimensional analysis to estimate minor losses due to start connectors; (b) to compare the accuracy of the developed models against models that are currently used for estimating minor losses; (c) to undertake simulations to assess the relevance of minor losses due to start connectors in hydraulics of subunits. Minor losses due to start connectors were separated into two components. A model was developed and validated to estimate minor losses due to the protrusion of start connectors inserted along a manifold. Two models were developed and validated to estimate minor losses that occur when water flows from a manifold into a lateral line through a start connector. The required data to develop and validate the models were obtained experimentally in laboratory. Although minor losses due to start connectors represented a relative small percentage of total head losses, such effects may be significant while undertaking rigorous hydraulic simulations that require accurate estimation of pressure losses

Test methods for characterising the water distribution from irrigation sprinklers: Design, evaluation and uncertainty analysis of an automated system

An automated system for indoor testing of irrigation sprinklers was developed and evaluated. The system was designed to test single sprinklers with jet lengths up to 18 m. The tests involve the use of 36 collectors (catch-cans) spaced at 0.5 m intervals along the jet radius. A single pressure transducer coupled to a manifold equipped with solenoid valves was employed to sequentially scan the water level in each collector. Radial application rates were determined based on water level measurements. Results obtained using the automated system were compared with those obtained using manual operation using mass measurements. Uncertainty analysis of the manual method was compared with the automated system. The automated system was found to be as reliable as the manually operated system for testing sprinklers. Although minor differences in the application rates measured by the two methods were detected, they did not cause appreciable differences in the distribution uniformity indicators used. The results presented will provide useful baseline for uncertainty analysis in irrigation sprinkler testing

Função de resposta do meloeiro a diferentes lâminas de irrigação e doses de nitrogênio Response function of melon under different irrigation and nitrogen levels

Objetivou-se estudar o efeito de lâminas de irrigação e doses de nitrogênio sobre o rendimento físico e econômico do meloeiro. O experimento foi conduzido em Pentecoste-CE, entre setembro e dezembro de 2002, em um delineamento experimental em blocos ao acaso no esquema de parcelas subdivididas. Os tratamentos constituíram-se da combinação entre quatro lâminas de irrigação (W1= 232,7; W2= 334,7; W3= 422,1; W4= 567,8 mm) e quatro níveis de adubação nitrogenada (N0= 0; N1= 75; N2= 150; N3= 300 kg ha-1), com quatro repetições. Foram avaliados dez modelos estatíticos e o que melhor se ajustou aos dados do experimento foi o polinomial quadrático, sem intercepto e sem interação entre os fatores lâminas de água (W) e doses de nitrogênio(N), conforme a equação de função de produção Y= 70,77509 W+34,16737 N0,05781 W²0,07612 N². Verificou-se que o fator água apresentou efeito significativo sobre o rendimento do meloeiro, enquanto o fator nitrogênio foi significativo apenas ao nível de 6,43%. Não houve interação significativa entre os fatores lâmina de irrigação e doses de nitrogênio. O máximo rendimento estimado foi de 25.496,1 kg ha-1. A receita líquida máxima estimada foi de R$3.353,24 ha-1 obtida com rendimento de 25.384,3 kg ha-1 de melão, utilizando-se 609,2 mm de água e 186,2 kg ha-1 de nitrogênio. A ótima eficiência econômica do uso da água estimada foi de 41,66 kg ha-1 mm-1, para uma dose de 186,2 kg ha-¹ de nitrogênio.<br>The objective of this work was to study the effect of water and nitrogen on the physical and economic yield of melon. The experiment was carried out in Pentecoste, Ceará State, Brazil, from September to December 2002, in a completely randomized experimental design, with blocks in split-plots. The main treatments were four water depths (W1= 232.7; W2= 334.7; W3= 422.1; W4= 567.8 mm) with four levels of nitrogen (N0= 0; N1= 75; N2= 150; N3= 300 kg ha-1). Ten statistic models were evaluated and the one that best adjusted to the experiment data was the quadratic polynomial model, without intercept and interaction among water (W) and nitrogen (N) factors as shown in the production function equation Y= 70,77509 W+34,16737 N0,05781 W²0,07612 N². Water presented a significant effect on productivity, while nitrogen was just significant at the level of 6.43$3,353.24 ha-1, obtained with 609.2 mm of water and 186.2 kg ha-1 of nitrogen, providing a yield of 25,384.3 kg ha-1. The economic efficiency of water use was estimated in 41.66 kg ha-1 mm-1, with the application of 186.2 kg ha-1 of nitrogen

Intercomparison testing and evaluation of sprinklers within the INITL

The International Network of Irrigation Testing Laboratories (INITL) undertook a sprinkler intercomparison testing exercise to generate data for an objective comparison of the performances of the different facilities and identify opportunities for further improvements. Three impact sprinklers were tested in four laboratories in accordance with established standards. The plots of flow rate-pressure profiles were found to be consistent, and correlated to those obtained from previous studies. Although there were slight variations in the measured flow rate data, the mean flow rates at each pressure level were the same for the three sprinklers, and the shapes of the radial distribution profiles were similar. The deviations of reconstituted flow rates (from the measured) of at least two tests in each facility were found to exceed the recommended limit. The sprinkler software developed by INITL was found to have a good correlation with a related commercial software program. DOI: 10.1061/(ASCE)IR.1943-4774.0000937. © 2015 American Society of Civil Engineers

Intercomparison dripper testing within the INITL

The International Network of Irrigation Testing Laboratories (INITL) undertook a laboratory intercomparison testing exercise of three sets of drippers in the period 2013 and 2014. The four testing facilities that participated in this exercise are based in following countries: Australia, Brazil, France and China. The objective of the testing programme was to compare results from different independent testing facilities to enable individual laboratories identify potential opportunities for improvement of their performances. This would also facilitate the INITL to make proposals for harmonisation of the testing methods. The maximum coefficient of variation, cv, at the manufacturer's recommended operating pressure of 100 kPa, was found to be 3.76%, which was significantly smaller than the 7% recommended by ISO 9261 [5] as the maximum allowable variation of the flow rate of the test sample. The emitter exponent was determined to be approximately 0.5 which is consistent with results obtained from past studies. At the operating pressure of 100 kPa, it was found that although the average flow rates from the participating laboratories were similar, there was a difference in the dispersion of data. Datasets for the 4 L h 1 dripper model fitted a normal distribution model, while on the other hand, some datasets for the 2 and 8 L h 1 dripper models were not normally distributed. A higher dispersion of measurements can be interpreted as a higher instability of the testing conditions. The variance for the 2 L h 1 dripper model was found to be homogeneous, while non-homogeneous for the other two models. The latter implies that at least one of the laboratories presented an uncertainty of measurement significantly different from the others. The measurement uncertainty undertaken in this study demonstrated that there were opportunities to improve the measurement process. Recommendations and suggestions for harmonisation of test procedures and improvements in individual laboratories are also identified in this paper