Irrigation
O. Raja; M. Parsinejad; M. Tajrishi
Abstract
Introduction Surface and groundwater conjunctively interact at different spatial or temporal scales within a plain. In many plain, surface and groundwater resources are used in combination in agriculture. Therefore, it is important to accurately predict the components of groundwater and surface ...
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Introduction Surface and groundwater conjunctively interact at different spatial or temporal scales within a plain. In many plain, surface and groundwater resources are used in combination in agriculture. Therefore, it is important to accurately predict the components of groundwater and surface water balance. Despite the rapid expansion of numerical models over the past two decades, there is still a need for comprehensive and integrated assessment of surface and groundwater components. In particular, the interconnection of both surface and groundwater models is important to connect both surface and groundwater, especially the water balance in the unsaturated root zone. In this study the effect of water recharge due to deep percolation from simultaneous supply of irrigation water from surface and groundwater sources, and rainfall from the SWAT model were used to simulate groundwater balance using the combined MDOFLOW-NWT model.Materials and Methods In this study, the effect of recharge values obtained from the SWAT model was analyzed to simulate the fluctuation of water table, and groundwater balance components using the integrated model of MODFLOW-NWT model in the Mahabad plain. One of the important steps in quantifying the impact of irrigation management, and the change in land-use on the surface and groundwater balance was the simulated recharge due to the deep percolation of rainfall and irrigation water. This was done by the SWAT model, and was used as the boundary condition to the MODFLOW-NWT model. Calibration and validation of groundwater model were also done by trial-and-error and automatic PEST methods. The simulation period was performed for 10 years from the hydrological year of 2009-2010 to 2018-2019, from which 6 and 4 years were used as the period for calibration and validation were from 2009-2010 to 2014-2015 and 2015-2016 to 2018-2019, respectively. Groundwater balance components are naturally different for different years. Therefore, the study was conducted for dry, wet, and normal years. Hydraulic conductivity and specific yield were the used as initial calibration parameters in the MODFLOW-NWT model.Results and Discussion The results showed a higher hydraulic conductivity and specific yield values for the aquifer was in the southern, central, and northeastern areas of the plain, and the lowest values were in the northern and near the outlet of the plain. After the calibration process, the results showed that an average, 9% of rainfall, and 36% of irrigated water percolate to the aquifer. These observations were confirmed based on a satisfactory and acceptable estimate of the water table level of the model for both calibration and validation periods. The statistical RMSE criteria for calibration and validation periods were 0.35 and 0.34 m, respectively. Also, the results of R2 and NSE criteria were estimated as 0.94 and 0.91 for the calibration period, and 0.93 and 0.89 for the validation period, which indicates that the model was properly calibrated and was well able to simulate groundwater level. The groundwater hydrographs developed from piezometers’ readings, show that the recharge values estimated by the SWAT model, considering the change in land use and irrigation management across the plain, were able to properly simulate groundwater level across the aquifer. Specifically, the studies showed a continuous drop in groundwater level created in the southern and southwestern regions of the aquifer (piezometers of Fakhrighah, Gorg tapeh, and Serah Haji Khosh) due to the presence of high-consumption crops such as apple and alfalfa, and the higher number of operation wells.ConclusionThe results of this study showed that the recharge values obtained from the calibrated SWAT model was crucial parameters for proper simulation of groundwater, and can significantly improve the model results. The results of the main components of the groundwater balance for different years showed that the amount of recharge due to the infiltration of rainfall, and irrigation were different for each year. Also, interactions between surface and groundwater resources vary from about 30 to 50 million cubic meters between years, indicating a significant interaction between the water resources. In general, the SWAT-MODFLOW-NWT model can be used as a practical tool for proper management of surface and groundwater resources under different management scenarios.
ghassem aghajani mazandarani
Abstract
Introduction: Better use of water and soil resources in paddy fields, increase in rice production and farmer's income, installation of subsurface drainage system is necessary. The main goalof these systems, are aeration conditions improvement prevention of water logging, yield increase, land use increase ...
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Introduction: Better use of water and soil resources in paddy fields, increase in rice production and farmer's income, installation of subsurface drainage system is necessary. The main goalof these systems, are aeration conditions improvement prevention of water logging, yield increase, land use increase and multiuse of the land. In different countries, installation of subsurface drainage cause yield increase and working condition on the land, but no research has been conducted in different depths and spacing. On the other hand, spacing and depth are the most important parameters in the installation of drainage systems, have a direct effect on incoming water into the drains. The aim of this research, is an investigation of the effect of subsurface drainage with different depths and spacing on discharge rate variation and water table fall, in order to analyze the improvement of water flow movement in the soil. Also, study the effect of different drainage systems on the increase of the canola yield as the second cultivation in these treatments have been compared.
Materials and Methods: To measure hydraulic conductivity in different depths, the auger holes have been dug (excavated). The saturated hydraulic conductivity in these holes wasdetermined using Ernst method (1950) before installation of drainage systems. In the drainage pilot plot of Sari Agricultural Sciences and Natural Resources University three subsurface drainage systems with mineral envelope have been installed. 1- The first one with the 0.9 m depth and 30 m spacing (D90 L30), 2- The second one with 0.65 m depth and 15 m spacing (D0.65 L15) and 3- The third one with 0.65 m depth and spacing (D0.65 L30) and one bi-level system with mineral envelope including four drains of 15 m spacing with 0.9 m and 0.65 m depths were installed alternatively. After auger hole equipment installations, in the middle spacing of two subsurface and water table reading possible, the water table fluctuation and drain outlet discharge rate from farm drains during canola growing season were measured on a daily basis. Also, canola yield during 4 years after drainage systems were monitored.
Results and Discution: The results showed that mean discharge rates of drainage systems have increased with time and in the fourth year it was better than first and second years. Duringthe second year, the highest discharge rate onthe first day was in the low depth treatment and after 3 days the discharge rates become the difference among less. In the third year, the discharge rates of high spacing drains (D0.65 L30) have become higher than of spacing drains (D0.65 L15) discharge rates. But, in the first day its discharge rate was less and one can conclude that it is due to horizontal flow. With passing time and soil structure improvement, one can observe better yield from drains with higher spacing (30 m) also. By performance of drainage and soil conditions improvement in the third and fourth year, the deeper drainage systems have becomes better and water table fall of deep drain discharge rate and soil condition improvement in these systems become higher. In bi-level drainage, by increasing deep percolation, the water table fall in this treatment increased with time. Also, based on monitoring water table, in the first and second years after 5th day and in the third and fourth years after 4th day the water tables of deep drains decreased to lower depth drains. Due to heavy soil in paddy fields and existence of hardpan, the performance of low depth drains in falling water table was better in the first years. With passing time and performance of drainage the conditions for water movement in the soil become better and performance of deep drainage systems improved and at the fourth year, deep drainage systems had better performance in draining water with respect to low depth drainage systems. Also, canola yield as second cultivation, has increased from first to fourth year and along with important of soil aeration conditions and performance of drainage systems, the grain yield hasincreased in different drainage treatments. The results showed a direct relationship between improvement of system performance and increase in grain yield. In the second year, grain yield increased in all treatments. On the other hand, the yield under drainage systems with deeper depth (D0.9 L30) even higher in the 2nd and 4th years than with low depth drain (D0.65 L30). This was because of more fall in water table levels during days after rainfall and also with next rainfall, saturation of soil up to surface layer in the plots with deeper drains were performed later and it may not reach up to thesoil surface.
Conclusion: Due to betterconditions of deep drains and with higher spacing in the improvement of paddy field use and also less environmental harm use of drains with higher spacing are recommended for these lands. On the other hand,a low increase in drain depth from 0.65 m to 0.9 m along with increase in spacing of30 m with respect to 15 m and even with 0.65 m depth, will have less cost. Due to decrease in the costs of drain installation with higher spacing, due to improvement of conditions, the performance of these systems in 2 to 3 years one can have cheaper drainage systems in the longest time and will improve the economic situation of farmers due to higher yield.
S. Hamzeh; AbdAli Naseri; H.A. Kashkuli
Abstract
Two issues of the drainage systems which are less studied in the literature are drainage in layered soils and bi-level derange systems. Hence, it is necessary to do more research in these topics. Therefore the present study was carried out under above conditions in the Imam Khomeini Farming and Industrial ...
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Two issues of the drainage systems which are less studied in the literature are drainage in layered soils and bi-level derange systems. Hence, it is necessary to do more research in these topics. Therefore the present study was carried out under above conditions in the Imam Khomeini Farming and Industrial Lands, located in the north of the Khuzestan province, Iran. In this area based on primary studies, lateral spacing was estimated about 70 m and they were installed at the depth of 2.1m. But after two years of establish these drainage systems, it was observed that due to existence a soil layer with a very low infiltration rate (less than 10 time in compare with its above and below layers) at the depth of 110 to 160 cm, drainage systems in 500ha of these fields had low performance. Then, in order to overcome with this problem, the implementation of bi-level drainage system was proposed. Hence, a new drain line was installed at the depth of 1.2m between the old drain lines. After establishment of these new drains one field was selected to evaluation the performance of this new system. In the selected field three rows of observation wells were installed (in total 20 observation wells). After equipment of these observation wells, water table fluctuation, inflow and outflow water values from the field were measured in 3 irrigation periods. Then the results of field observations were compared with the obtained results from analytical solution in the literature. Results show with establish new drain lines the problem of these fields are solved and the water table profile will drop-off to the below of root zone in less than 36hr. Also it was concluded that the rate of water table decline by moving from the end of field to the open collector of field will be increased and the discharge of deep drains are more than low-deep rains. Results show that analytical solution is not able to predict the water table profile with well accuracy and predicted values by this equation only in a small area of water table profile were consistent with the observed values in the field. The main reason of this difference was the specific situation of layers of the soil.
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.
