Presenting empirical equations for estimating Manning roughness coefficient in furrow irrigation in different irrigation phases

Articles in Press

Document Type : Research Paper

Authors

Department of Irrigation and Reclamation Engineering, College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran.

Abstract

This study aimed to investigate the temporal variation of the roughness coefficient and its estimation in different phases and events of irrigation using empirical relations. For this purpose, six inflow rates in two flow categories, low and high. three consecutive irrigation events, advance and storage phases, two irrigation intervals and two types of soil texture were investigated. Next, the correlation between roughness and these parameters was investigated using statistical tests. Then, regression equations were developed to estimate roughness in different irrigation phases. The results indicated that the advance time and the size of clods before irrigation had a high correlation and the slope, initial soil moisture and the size of clods after irrigation had a low correlation with the Manning roughness coefficient data in the whole irrigation event. The roughness coefficient of the advance phase also had the highest correlation with the advance time. The highest and lowest correlation coefficients between the parameters and roughness coefficient of the storage phase were related to advance time and inflow rate respectively, which shows high correlation and direct relationship between advance time and roughness and weak correlation and inverse relationship between flow rate and roughness. The average values of R2, RMSE, and NRMSE indices in the provided relationships were 0.87, 0.014, and 26.97%, respectively, which indicated the appropriate accuracy of these relationships. Finally, it was suggested to conduct similar studies in different field and hydraulic conditions so that the presented relations are more comprehensive and can be recommended in other fields.

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Iranian Journal of Soil and Water Research

Articles in Press, Accepted Manuscript
Available Online from 10 June 2024

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