A. Firoozi; seyed majid mirlatifi; Hamed Ebrahimian
Abstract
Introduction: Agriculture consumes a large portion of groundwater resources. In order to understand the status of groundwater resources in a basin and to optimize its management, it is necessary to carry out an accurate examination of the fluctuations in the groundwater levels. Recharging groundwater ...
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Introduction: Agriculture consumes a large portion of groundwater resources. In order to understand the status of groundwater resources in a basin and to optimize its management, it is necessary to carry out an accurate examination of the fluctuations in the groundwater levels. Recharging groundwater aquifers is one of the main strategies for water resources management which its accurate estimation plays a crucial role in the proper management of ground water resources. That portion of the excess irrigation water which becomes in the form of deep percolation should not be considered as wasted water, if its quality is not adversely reduced and it enters and recharges groundwater aquifers. The question is whether deep percolations resulting from irrigating farms with low application efficiencies and poor irrigation management in the Urmia basin would finally recharge ground water aquifers or not. In order to provide a solution to the aforementioned question, after calibrating HYDRUS-1D model, it was used to estimate the fluctuations of the levels of the water tables as a results of irrigations or rainfalls in a number of wheat, barley and sugar beet fields located in Miandoab and Mahabad regions where all agricultural practices were managed and carried out by the local farmers.
Materials and Methods: In order to ascertain the effects of irrigation on the groundwater recharge, the required field data was collected from nine agricultural fields including one wheat farm, three barley farms, and three sugar beet farms, all located in the Miandoab region and two wheat fields located in the Mahabad region. All the water balance parameters for each one of the fields were measured in the studied fields, including the depth of irrigation at each irrigation event by using WSC flumes. The Surface runoff from the studied farms was considered as negligible, since all the fields were irrigated using closed end borders. The evapotranspiration of wheat, barley and sugar beet were calculated in the regions using the CROPWAT8.0 model.
The soil texture of each of the study fields were determined by hydrometric method in the laboratory and then soil hydraulic parameters were estimated by ROSETTA model. The soil moisture of all the fields during the growing season were measured using a PR2 moisture meter instrument measuring soil moisture at various depths up to 105 cm below the soil surface. The amount of deep percolation occurring during the growing season was simulated by the HYDRUS-1D model. The soil water content measured by PR2 (Delta-T Device) probe were used for HYDRUS-1D model calibration and validation using the inverse solution method. Because of the occurrence of rainfall, irrigation and evapotranspiration, the atmospheric boundary condition was selected as the upper boundary condition and free drainage was considered as the lower boundary condition in order to estimate the groundwater recharge, assuming that water passes through and below the root zone. In areas with shallow ground water depth, constant flow with zero flux was chosen as the lower boundary condition in order to determine the fluctuations of the ground water level. Since the groundwater level in this case study was shallow, zero flux was considered as the lower boundary condition. The soil moisture content before irrigation was selected as the modelling initial condition.
Result and Discussion: The HYDRUS-1D model was calibrated by comparing the model estimated soil moisture contents with the corresponding measured values which indicated the coefficient of determination (R2) and root mean square error (RMSE) values ranging from 0.6 to 0.85 and 0.17 to 0.033 (), respectively. Another set of measured soil moisture data which was collected by using PR2 instrument and was not used for calibrating the model, was applied to verify the model simulation of the soil moisture content. Comparing the measured and simulated soil moisture contents at this verification stage resulted in coefficient of determination (R2) and root mean square error (RMSE) values ranging from 0.62 to 0.88 and 0.002 to 0.023 (), respectively. There was no significant difference between the predicted and measured soil moisture data in all the fields (P-value> 0.05). The minimum and the maximum coefficient of determinations in the validation stage were obtained in the T5 field with a silty loam soil and in the H3 field having a sandy loam soil. The accuracy of the model performance after it was calibrated and verified using the collected field data, was appropriate for estimating the soil water content during the growing season. The model was used to simulate the soil water contents from the soil surface to the depth of the water table during the growing season to evaluate the degree of aquifer recharge if any happened. The soil moisture front advanced to a depth of 0.7 m below the soil surface in the M1 field and to 4.7 m in the T1field. The amount of groundwater recharge varied from field to field depending on each field’s soil type, cultivation and irrigation management including the depth and the time of the irrigations. The amount of groundwater recharge increased by decreasing crop evapotranspiration. The percentage of ground water recharge in N1, M1 and M2 fields due to limited availability of water resources which resulted in deficit irrigation was very low. The irrigation water requirements estimated by the CROPWAT model for the aforementioned fields were more than the depths of the irrigation water applied by the farmers. The CROPWAT model estimated the irrigation water requirements during the growing season for wheat, barley and sugar beet in the Miandoab region to be 308, 273 and 736 mm, respectively. However, the depths of irrigation applied to such farms ranged from 306 to 500 mm.
Conclusion: This research was conducted to ascertain the effects of local farmer’s irrigation management practices considered as poor management in some areas with plenty of water resources available and rainfall on the amount of the groundwater recharge occurring in the regions studied located in the Lake Urmia basin. The simulated groundwater recharge by the HYDRUS-1D model indicated that the amount of recharge varied from field to field depending on soil type, cultivation and irrigation management practices. In all the fields, the highest amount of groundwater recharge occurred when the crop evapotranspiration was low and therefore, enhancing deep percolation to take place. The highest percentage of groundwater recharge was 28% of the sum of the irrigation and rainfall depths which occurred in the barley field (H3).
Mehrnaz Amini; Hamed Ebrahimian
Abstract
Introduction: Water scarcity is an important challenge worldwide, especially in arid and semi-arid regions. Water-scarce countries will have to rely more on the use of non-conventional water resources to partly alleviate water scarcity. The reuse of wastewater for irrigation is considered to be beneficial ...
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Introduction: Water scarcity is an important challenge worldwide, especially in arid and semi-arid regions. Water-scarce countries will have to rely more on the use of non-conventional water resources to partly alleviate water scarcity. The reuse of wastewater for irrigation is considered to be beneficial for crop production, and due to its nitrogen and phosphorus content, it can help to reduce the requirements for commercial fertilizers. However, under certain conditions, this type of water if not well managed, can have negative impacts on cultivated crops and soils, particularly on soil salinity and sodicity, and may pollute groundwater, as a result of high nitrogen concentration of most treated wastewater. Besides nitrogen (N) contamination of surface and ground waters has become a serious and global environmental problem. The risk of groundwater contamination by N depends largely on the N input to agricultural fields in the form of inorganic fertilizers and on its effective use of agricultural crops. Improvement of irrigation and nitrogen application management during the growing period can be achieved using mathematical models. The goal of this study was to assess the effects of irrigation with raw and treated wastewater by using the HYDRUS-1D model for simulation of water and nitrate transport in a maize field.
Materials and Methods: The experimental station of the College of Agriculture and Natural Resources, University of Tehran, was considered as a case study. The information of maize growing season in 2010, as well as raw and treated wastewater of Ekbatan housing complex was considered as a source of irrigation water for simulation of water and nutrient movements in the soil by HYDRUS-1D software package. HYDRUS-1D numerically solved the Richards equation for describing the variably-saturated water flow in a radially symmetric domain and the convection-dispersion equation for solute transport. The soil hydraulic properties were described using the van Genuchten-Mualem model. Since the direct measurement of soil hydraulic parameters in the field or laboratory is time consuming and costly, they were estimated using the ROSETTA model, using particle size and bulk density data determined on soil samples taken from depths of 0-20, 20-40, 40-60 cm.
Results and Discussion: The results showed that water contents increased after any irrigation event, and then decreased gradually during the following hours and days, until the next irrigation took place. Deeper depths showed smaller water content variations since root water uptake and soil evaporation were more pronounced at shallower depths. Simulated plant water uptake was estimated to be 80% of the water application, indicating the high irrigation efficiency of the system. Cumulative deep percolation (DP) values increased rapidly at around 43 days after planting. This is obtained due to higher irrigation water depth applied at irrigation events after this time because of rapid growth of maize crop that is occurring due to increase air temperature at this time. Simulated deep percolation reached 6.98 cm which is 13% of the total amount of water applied during the growing season. Simulation results showed that N leaching at 60 cm depth for about 7.61 and 2.64 kg N ha-1 for raw and treated wastewater, respectively. Nitrogen concentration for raw and treated wastewater decreased due to root nutrient uptake. The results also showed that the crop N uptake was 76.2% and 81.9% of total N input (TNI) during the growing season, while 19.4% and 14.5% of TNI was retained in the soil at the end of the season for raw and treated wastewater, respectively.
Conclusion: The HYDRUS-1D model was used to simulate the transport of N-NO3- under the raw and treated wastewater application in the soil. Simulation results provided detailed moisture and N regime, as well as bottom boundary flux for percolation and N leaching estimation. N leaching is closely correlated with vertical water flow. The N leaching distributions at the bottom of the soil profile (60 cm) are similar to the corresponding water flux distributions. The results also showed that the crop N uptake was 130 and 60 kg N ha-1 during the growing season for raw and treated wastewater, respectively. As the results showed wastewater can use as a source of N for crops and it can help to reduce the requirements for commercial fertilizers, and decrease their negative environmental impacts. It is suggested that the model parameters can be measured practically, in order to be used for model calibration and validation. Besides, the simulation can be done for a longer period of time to evaluate the effect of rainfall and different cultivations on solute transport.
S. Vazirpour; H. Ebrahimian; H. Rafiee; F. Mirzaei Asl Shirkohi
Abstract
Introduction: Infiltration is one of the most important parameters affecting irrigation. For this reason, measuring and estimating this parameter is very important, particularly when designing and managing irrigation systems. Infiltration affects water flow and solute transport in the soil surface and ...
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Introduction: Infiltration is one of the most important parameters affecting irrigation. For this reason, measuring and estimating this parameter is very important, particularly when designing and managing irrigation systems. Infiltration affects water flow and solute transport in the soil surface and subsurface. Due to temporal and spatial variability, Many measurements are needed to explain the average soil infiltration characteristics under field conditions. Stochastic characteristics of the different natural phenomena led to the application of random variables and time series in predicting the performance of these phenomena. Time-series analysis is a simple and efficient method for prediction, which is widely used in various sciences. However, a few researches have investigated the time-series modeling to predict soil infiltration characteristics. In this study, capability of time series in estimating infiltration rate for different soil textures was evaluated.
Materials and methods: For this purpose, the 60 and 120 minutes data of double ring infiltrometer test in Lali plain, Khuzestan, Iran, with its proposed time intervals (0, 1, 3, 5, 10, 15, 20, 30, 45, 60, 80, 100, 120, 150, 180, 210, 240 minutes) were used to predict cumulative infiltration until the end of the experiment time for heavy (clay), medium (loam) and light (sand) soil textures. Moreover, used parameters of Kostiakov-Lewis equation recommended by NRCS, 24 hours cumulative infiltration curves were applied in time-series modeling for six different soil textures (clay, clay loam, silty, silty loam, sandy loam and sand). Different time-series models including Autoregressive (AR), Moving Average (MA), Autoregressive Moving Average (ARMA), autoregressive integrated moving average (ARIMA), ARMA model with eXogenous variables (ARMAX) and AR model with eXogenous variables (ARX) were evaluated in predicting cumulative infiltration. Autocorrelation and partial autocorrelation charts for each variable time-series models were investigated. The evaluation indices were the coefficient of determination (R2), root of mean square error (RMSE) and standard error (SE).
Results and discussion: The results showed that the AR(p), ARX(p,x) and ARMAX(p,q,x) time series models with various degrees 1, 2, 3 successfully predicted infiltration rates for duration of the test in different soils. Significant correlation between actual and estimated values of cumulative infiltration was almost obtained. The values of SE varied between 2 and 5 percent for three soil textures in Lali plain. Reducing input data from two hours to one hour did not have major impact on infiltration prediction. The results of 24 hours cumulative infiltration also indicated standard error of estimated infiltration varied between 2 and 21% for six different soil textures. Similarly, there was a very good correlation between the actual and predicted values of 24 hours cumulative infiltration. The prediction error increased with increasing prediction time (4 hours vs. 24 hours). The time-series models had accurate performances to predict cumulative infiltration until 12 hours, therefore, they would be as a useful tool to predict soil infiltration characteristics for irrigation purposes. The RMSE values for predicting 24 hours cumulative infiltration were 0.5, 2.6, 4.1, 4.9, 7.5 and 11.8 cm for clay, clay loam, silt, silty loam, sandy loam and sand, respectively. The SE values also were 2.6, 11.7, 13.9, 14.9, 17.2 and 21.6 % for clay, clay loam, silt, silty loam, sandy loam and sand, respectively. Time-series modeling showed better performance in heavy and moderate soils than in light soils. However, the performance of the time-series modeling for predicting infiltration for the double ring test with four hours experiment time was better for light soil textures as compared to heavy and moderate soil textures. Therefore, more studies are needed to investigate the capability of time series modeling to predict infiltration with more experiment data, particularly for heavy and moderate soil textures.
Conclusion: The results indicated that the experiment time of the double ring test could be reduced from four to one hour by using time series models in various soil textures and consequently the cost of soil infiltration measurements would be decreased. Using initial 120 min infiltration data, the time-series models could successfully predict the 12 hours cumulative infiltration. Comparison between the results of times-series models and actual data indicated the application of time-series models in predicting soil infiltration characteristics was efficient.
ali javadi; M. Mashal; M.H. Ebrahimian
Abstract
Infiltration is a complex process that changed by initial moisture and water head on the soil surface. The main objective of this study was to estimate the coefficients of infiltration equations, Kostiakov-Lewis, Philip and Horton, and evaluate the sensitivity of these equations and their coefficients ...
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Infiltration is a complex process that changed by initial moisture and water head on the soil surface. The main objective of this study was to estimate the coefficients of infiltration equations, Kostiakov-Lewis, Philip and Horton, and evaluate the sensitivity of these equations and their coefficients under various initial conditions (initial moisture soil) and boundary (water head on soil surface). Therefore, one-and two-dimensional infiltration for basin (or border) irrigation were simulated by changing the initial soil moisture and water head on soil surface from irrigation to other irrigation using the solution of the Richards’ equation (HYDRUS model). To determine the coefficients of infiltration equations, outputs of the HYDRUS model (cumulative infiltration over time) were fitted using the Excel Solver. Comparison of infiltration sensitivity equations and their coefficients in one-and two-dimensional infiltration showed infiltration equations and their sensitivity coefficients were similar function but quantitatively in most cases sensitive two-dimensional equations and their coefficients were greater than one dimension. In both dimensions the soil adsorption coefficient Philip equation as the sensitive coefficient and Horton equation as the sensitive equation under various initial moisture soil and water head on soil surface were identified.
M. Hassanli; H. Ebrahimian; M. Parsinejad
Abstract
Using of saline water for irrigation of crops is known as a strategy of on-farm irrigation water management. In this study, the cyclic using of saline and fresh water and its effect on soil salinity were investigated. Field experiments were carried out in randomized complete block design under drip irrigation ...
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Using of saline water for irrigation of crops is known as a strategy of on-farm irrigation water management. In this study, the cyclic using of saline and fresh water and its effect on soil salinity were investigated. Field experiments were carried out in randomized complete block design under drip irrigation for maize crop with 9 treatments. The treatments were based on alternative irrigation management of saline and fresh water use on three salinity levels 0.4, 3.5 and 5.7 dS/m and freshwater application in every one, three and five saline water application (1:1, 3:1 and 5:1, respectively). The results showed that in 1:1 management, soil salinity at the end of growing season compared with the beginning of growing season did not change considerably (reducing of 1.0% and 17.9% for 1S1:1F and 1S2:1F). In 3S2:1F and 5S2:1F treatments, the amount and frequency of fresh water was not enough to remove salts from the soil and at the end of growing season, salt accumulation was seen in soil profile (increasing of 39.0% and 46.2% in soil salinity). In 3S1:1F and 5S1:1F treatments, soil salinity increased 17.9% and 31.6%, respectively, while increasing of soil salinity in S1 treatment was 40.7%. Thus, by 4 irrigations with fresh water in 3S1:1F treatment and 2 irrigations with fresh water in 5S1:1F treatment, reducing of 22.8% and 9.1% in soil salinity was seen in compared with S1 treatment.
Mohammad Ghorbanian
Abstract
Many numerical and analytical models have been developed for estimation of soil water distribution in order to increase water use efficiency in drip irrigation. Accurate solution of well-known soil water equation, Richard’s equation, in these models cause more accurate estimation of soil wetting front. ...
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Many numerical and analytical models have been developed for estimation of soil water distribution in order to increase water use efficiency in drip irrigation. Accurate solution of well-known soil water equation, Richard’s equation, in these models cause more accurate estimation of soil wetting front. The purpose of this study was to evaluate finite difference and finite element methods to numerical solution of Richard’s equation for simulating soil water flow around dripper via comparing HYDRUS-2D and SEEP/W numerical models. Experiments were carried out to collect required data to investigate the advance of moisture front inside a Plexiglas box filled with a silt loam soil in central laboratory of water researches in University of Tehran. Wetting front advance at different time intervals were plotted on the transparent Plexiglas box walls. The wetting front around the emitters, for pressures 1.5 and 2.2 meters (equivalent to 4.5 and 6.3 liters per hour, respectively), were measured. Comparison of two simulation models, HYDRUS-2DandSEEP/W, showed that HYDRUS-2D model (finite difference solution method) with higher determination coefficient and lower root mean square error coefficient had better performance to simulate wetted area dimensions for both surface and subsurface drip irrigation.
Z. Taghizadeh; V.R. Verdinejad; H. Ebrahimian; N. Khanmohammadi
Abstract
The low irrigation application efficiency is the major problem of surface irrigation systems due to weak management and poor design. In this research, in order to analyze the performance of furrow irrigation system, a field experiment was conducted during maize growing season. Three furrow irrigation ...
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The low irrigation application efficiency is the major problem of surface irrigation systems due to weak management and poor design. In this research, in order to analyze the performance of furrow irrigation system, a field experiment was conducted during maize growing season. Three furrow irrigation methods; conventional furrow irrigation, fixed alternate furrow irrigation and variable alternate furrow irrigation were considered to collect field data and, then, to evaluate the performance of WinSRFR (surface irrigation model). This model was calibrated and evaluated based on the experimental data with Zero-Inertia (ZI) and Kinematic Wave (KW) solutions. The sensitivity analysis of WinSRFR showed that the most sensitive parameters were inflow rate, cutoff time and parameters of the infiltration equation, respectively. There was a small difference between ZI and KW to estimate advance time, runoff and infiltration due to high field slope. The minimum absolute error for estimation of advance times was obtained about 1.5% (0.8 minute). The minimum absolute error in estimating runoff and infiltration were 5.7 and 5.0%, respectively. Using operations analysis of WinSRFR, the iso-performance contour plots of furrow irrigation system was obtained to optimize cutoff time and inflow rate under maximizing of application efficiency and distribution uniformity and minimizing of runoff and deep percolation. Application efficiency iso-performance contour plot of fixed alternate furrow irrigation, indicated by managing of cutoff time and inflow rate, application efficiency could be increasing from 54.5% in current evaluation to 74%, provided water supply of Dreq. Also based on this contour plot, increasing of application efficiency more than 74% was impossible provided water supply of Dreq, under current furrow geometry parameters and it was possible with changing furrow geometry parameters.
V. R. Verdinejad; H. Ebrahimiam; H. Ahmadi
Abstract
A transient drainage simulation model, SWAP, was used to evaluate the performance of subsurface drainage system. SWAP model was calibrated by measured daily data including water table depth, drain discharge rate and soil and water drain salinity collected from Behshahr Ran drainage system for 120 days ...
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A transient drainage simulation model, SWAP, was used to evaluate the performance of subsurface drainage system. SWAP model was calibrated by measured daily data including water table depth, drain discharge rate and soil and water drain salinity collected from Behshahr Ran drainage system for 120 days during 1385. Calibration of SWAP model was done by inverse modeling via linking with WinPEST model. In order to calibrate drainage quantity parameters, two objective functions were defined to minimize difference between measured and simulated values of the water table depth and drain discharge rate, simultaneously. To calibrate drainage quality parameters, another objective function was also defined to minimize difference between measured and simulated values of soil salinity. There were good agreements between measured and simulated values of drain discharge rate and water table depth. The absolute error of estimation was 7 and 4 % for water table depth and drain discharge rate, respectively. Measured cumulative drainage was 7.5 % (5.3 mm) greater than its simulated value. The SWAP model could also simulate soil and drainage water salinity with a reasonable accuracy. The results of this study indicated that the performance of the SWAP model could be considerably improved using inverse modeling.
H. Ebrahimian; B. Ghanbarian-Alavijeh; F. Abbasi; A. Hourfar
Abstract
چکیده
نفوذ، مهمترینترین و مشکلترین پارامتر ارزیابی سامانههای آبیاری سطحی است. اهمیت دانستن معادله نفوذ جهت تشریح هیدرولیک آبیاری سطحی، همراه با مشکلات تخمین قابل ...
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چکیده
نفوذ، مهمترینترین و مشکلترین پارامتر ارزیابی سامانههای آبیاری سطحی است. اهمیت دانستن معادله نفوذ جهت تشریح هیدرولیک آبیاری سطحی، همراه با مشکلات تخمین قابل اطمینان پارامترهای آن، موجب صرف وقت و هزینه زیادی برای طراحی یک سامانه آبیاری میشود. هدف از این مطالعه، ارزیابی روشهای مختلف تخمین پارامترهای نفوذپذیری و ارائه روش دو نقطهای جدیدی براساس معادله نفوذ فیلیپ است. در این راستا از هفت سری داده صحرایی با شرایط مختلف مزرعهای از جمله طول، شیب و دبی ورودی استفاده گردید. همچنین با استفاده از مدل هیدرودینامیک نرم افزار SIRMOD و با تخمین پارامترهای معادله نفوذ به روش پیشنهادی و روشهای دو نقطهای الیوت و واکر، پیشروی بِنامی و اُفِن، یک نقطهای شپارد و همکاران و یک نقطهای والیانتزاس و همکاران، مراحل پیشروی و پسروی آبیاری شبیهسازی شدند تا دقت روشهای مختلف تخمین پارامترهای معادله نفوذ مورد بررسی قرار گیرد. نتایج نشان داد که در برآورد میزان آب نفوذیافته به خاک در آبیاری نواری روش پیشنهادی (8/4درصد) و در آبیاری جویچهای روش شپارد و همکاران (9/13درصد) و روش پیشنهادی (2/14درصد) دارای کمترین خطای نسبی میباشند. در پیشبینی مرحله پیشروی در آبیاری جویچهای و نواری به ترتیب روش پیشروی بنامی و افن (5/19درصد) و روش پیشنهادی (6/6درصد) و در پیشبینی مرحله پسروی در آبیاری جویچهای و نواری به ترتیب روش شپارد و همکاران (3/1درصد) و روش پیشنهادی (2/2درصد) دارای کمترین خطای استاندارد بودند.
واژههای کلیدی: روش دو نقطهای، تخمین پارامترهای نفوذ، آبیاری جویچهای، آبیاری نواری
H. Ebrahimian; A. Liaghat; M. Parsinejad; M. Akram
Abstract
Abstract
By evaluating the performance of the current drainage systems and exploration of their strengths and weaknesses a comprehensive perspective can be given to designers and organizers for optimum design and implementation of drainage systems for future plans. This study was conducted to evaluate ...
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Abstract
By evaluating the performance of the current drainage systems and exploration of their strengths and weaknesses a comprehensive perspective can be given to designers and organizers for optimum design and implementation of drainage systems for future plans. This study was conducted to evaluate the performance of subsurface drainage systems using rice husk as envelope in Behshahr, a coastal region in the northern part of Iran. For this purpose, eleven piezometers were installed between two subsurface drains designated as S3PD14 and S3PD15. Subsurface drainage system was monitored during rainfall seasons in 1383 and 1385. Parameters such as daily water table fluctuations and drain discharge rate were recorded. The overall conclusion was that subsurface drainage system performance was not satisfactory due to poor control of water table depth and low water discharge, which was mainly because of the drain envelope clogging. Therefore, the Hooghoudt’s equation should not be used for evaluation of design parameters, due to the fact that this equation is only valid for normal conditions (envelope without clogging).
Key words: Subsurface drainage, Rice husk envelope, Water table, Discharge rate, Behshahr, Iran