<p>The volume balance is one of the simple model in surface irrigation. The shape factors are necessary in this model. In this research, a full hydrodynamic model based on the numerical solution of Saint–Venant equations are described to calculate the shape factors and investigate their time variation in different soil textures under furrow irrigation. The results showed that the range of surface shape factor variation was more in heavy soils and also it increased at the first of advance phase and then its variations decreased. The subsurface shape factor had a decreasing trend in heavy soil and increasing trend in medium and light soils. The sensitivity degree of shape factors to different parameters were not the same, so that the surface shape factor and the subsurface shape factor were the most sensitive to <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40996_2025_1883_Article_IEq1.gif" Format="GIF" Height="12" Rendition="HTML" Resolution="72" Type="Linedraw" Width="17" /> </InlineMediaObject> <EquationSource Format="TEX">$\rho_{2}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>ρ</mi> <mn>2</mn> </msub> </math></EquationSource> </InlineEquation> in sandy soil and also the surface shape factor was the most sensitive to geometric shape factors of furrow and <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40996_2025_1883_Article_IEq1.gif" Format="GIF" Height="12" Rendition="HTML" Resolution="72" Type="Linedraw" Width="17" /> </InlineMediaObject> <EquationSource Format="TEX">$\rho_{2}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>ρ</mi> <mn>2</mn> </msub> </math></EquationSource> </InlineEquation> are geometric shape factors of furrow) and subsurface shape factor was not sensitive to any of parameters in clay soil. To validate the proposed method, field data that had been measured in previous research as reported (Esfandiari in Evaluation of furrow irrigation models for south-east Australia, Ph.D. Dissertation, University of Western Sydney, 1995) were used as a criterion for observational results. Then, using the proposed method and time measurements of surface and subsurface storage coefficients and their calculation, the advance time in terms of time was obtained. According to the comparison of the results obtained from these calculations with observational data, it was concluded that the proposed method measures the advance time with less error than the case where constant coefficients are considered. The shape factors calculated using the hydrodynamic model made the precision of the volume balance model increase up to 7%. Using the results of this research in the field, furrow irrigation can be designed with more time than the normal volume balance model, but measuring some parameters such as the geometric coefficients of the furrow may be difficult, which is the main limitation of this research.</p>

Investigation of Time Variation of Shape Factors of Volume Balance Model in Furrow Irrigation by Full Hydrodynamic Model

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发表日期：

2025年6月3日

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Kaveh Ostad-Ali-Askari,
Mohammad Shayannejad

摘要

The volume balance is one of the simple model in surface irrigation. The shape factors are necessary in this model. In this research, a full hydrodynamic model based on the numerical solution of Saint–Venant equations are described to calculate the shape factors and investigate their time variation in different soil textures under furrow irrigation. The results showed that the range of surface shape factor variation was more in heavy soils and also it increased at the first of advance phase and then its variations decreased. The subsurface shape factor had a decreasing trend in heavy soil and increasing trend in medium and light soils. The sensitivity degree of shape factors to different parameters were not the same, so that the surface shape factor and the subsurface shape factor were the most sensitive to $\rho_{2}$ $ρ_{2}$ in sandy soil and also the surface shape factor was the most sensitive to geometric shape factors of furrow and $\rho_{2}$ $ρ_{2}$ are geometric shape factors of furrow) and subsurface shape factor was not sensitive to any of parameters in clay soil. To validate the proposed method, field data that had been measured in previous research as reported (Esfandiari in Evaluation of furrow irrigation models for south-east Australia, Ph.D. Dissertation, University of Western Sydney, 1995) were used as a criterion for observational results. Then, using the proposed method and time measurements of surface and subsurface storage coefficients and their calculation, the advance time in terms of time was obtained. According to the comparison of the results obtained from these calculations with observational data, it was concluded that the proposed method measures the advance time with less error than the case where constant coefficients are considered. The shape factors calculated using the hydrodynamic model made the precision of the volume balance model increase up to 7%. Using the results of this research in the field, furrow irrigation can be designed with more time than the normal volume balance model, but measuring some parameters such as the geometric coefficients of the furrow may be difficult, which is the main limitation of this research.