Functional Performance of Parallel Drain Subsurface System in Waterlogged Paddy Field

Waterlogging induced salinity is a common problem in many command areas of irrigation projects. Subsurface drainage improves the productivity of poorly drained soils by decreasing the water table, providing greater soil aeration, improving root zone soil salinity and enhancing the crop yield. A pilot study has been conducted to explore the functional performance of the parallel drain subsurface system in waterlogged paddy field by considering the lateral drain spacing and drain depth are the factors influences the soil properties. This experiment was carried out in farmers’ field at Sembari village, Lalgudi, Tamil Nadu, India in waterlogged paddy field during October 2020 to February 2021. Treatments of this study consisted the combination of three lateral drains spacing of 7.5 m, 10.0 m and 12.5 m and two drain depths of 60 cm and 80 cm and a control plot. This study investigated the changes in soil properties, depth to water table, drainage coefficient and crop behaviors after installation of the system. Reduction in Soil pH, removal of slats in drain water, lowering the depth to water table and higher drainage coefficient recorded for narrow lateral drain spacing and deeper drain depth treatment has improved the root zone environment for crop growth. Paddy has been established very well in terms of plant height and number of tillers per plant in S1D2 (7.5 m drain spacing and 80 cm drain depth) treatment which was also reflected in grain yield and straw yield over undrained paddy field yield. Based on the results, it is recommended to install parallel drain subsurface system at 7.5 m drain spacing and 80 cm drain depth in the study area.

Hydrodynamic model of the formation of horizontal drainage runoff on drainless and slightly drained irrigated lands in the dry steppe zone of Ukraine

The article presents the results of the research, which are the basis of making a hydrodynamic model of the formation of drainage runoff of closed horizontal drainage on drainless and slightly drained irrigated lands in the dry steppe zone of Ukraine. The relevance of the research is in their need when designing the systems of horizontal drainage, determining drain spacing, modes of operation and the evaluation of drainage efficiency during its operation when irrigating with the use of modern sprinklers from a closed farm network. The objective of the research is to develop a generalized hydrodynamic model of formation of closed horizontal drainage runoff when irrigating from a closed farm network on drainless and slightly drained lands, which are typical for the watershed plains and coastal lowlands of the dry steppe zone of Ukraine. The task of the research to determine the basic conditions and factors of formation of horizontal drainage runoff, to specify the structure of groundwater inflow to the drains when having optimal drain spacing in the closed farm network and to define the prospects and areas of further research. Research methods and techniques: long-term (1975-2020) field experiments on drained areas with different drain spacing in typical hydrogeological conditions for watersheds and coastal lowlands; water balance studies; theoretical research methods (analysis and synthesis, comparison, generalization, zoning); to determine the structure of groundwater inflow to the drains, the method of electrohydrodynamic analogies when using the laboratory integrator EGDA 9/60 was applied. As a result of the research it was determined that in the conditions of a closed water farm network it is possible to increase drain spacing from 120-220 m to 240-400 m. When studying all the conditions of drainless and slightly drained watershed plains and coastal lowlands, the main sources forming the regime of groundwater and drainage runoff are the precipitation of 420 mm or 55.0% of water input, irrigation water - 340 mm or 45.0%, including 266 mm or 35,0% from irrigation and 75 mm or 10,0% from filtration from the canals. The analysis of the hydrodynamic model of drainage runoff formation shows that when having drain spacing as 240-400 m, the inflow from the zone located above the bottom of the drain is 2.6-4.8% of the total inflow to the drain. The ascending flow under the bottom of the drain enters it at an average angle of 600 and in all variants of drain spacing is 95.2-97.2% of the total inflow. When drain spacing increases from 240 to 300-400 m, the horizontal inflow from the area located below the bottom of the drain decreases with a corresponding increase in the ascending flow under the bottom of the drain. The average width of the ascending flow to the drain at the edge of the active zone of groundwater (9.0-10.0 m below the drain) is 13.0-20.0 m. The resulting model complements the existing theoretical and methodological knowledge base for designing horizontal drainage and is necessary in perspective researches on the formation of expert systems for optimization of the parameters and modes of irrigation and drainage functioning when applying modern broadcast sprinkler equipment irrigating from the closed farm network.

Simulation of Soil Salinity using DRAINMOD-S Model under Subsurface Drainage System in Arid and Semi-arid Regions of Punjab, India

Water management simulation model DRAINMOD-S was calibrated (1995-96) and validated (1997) using 3-year experimental field data (1995-1997) from the installed subsurface drainage system at 1.8 m drain depth with 40, 60, and 80 m drain spacing at Golewala watershed, Faridkot, Punjab, India. Sensitivity analysis of the model parameters revealed that lateral saturated hydraulic conductivity, drain depth, and drain spacing are the most effective parameters in changing the model output. The root means square error, efficiency, and coefficient of determination between observed and simulated soil salinity ranged from 0.01to 0.06 dS.m-1, 0.647 to 0.834 dS.m-1, and 0.957 to 0.999 dS.m-1 for three drain spacings (40, 60, and 80 m), respectively, during calibration and validation period. The calibrated and validated model was used to predict the soil salinity (EC) for five consecutive years (1998-2003). The average soil salinity of root zone (300-600 mm), (600-900 mm), and (900-1200 mm) decreased from January 1998 to December 2003. The predicted values of soil salinity were found to decrease from 2.23, 2.34, and 1.92 dS.m-1 to 1.68 dS.m-1, 1.70, and 1.42 dS.m-1 for 40 m drain spacing at root zone depth of 300-600 mm, 600-900 mm, and 900-1200 mm, respectively. Similarly, the salinity values for the same period and root zone depth were found to decrease from 2.20, 2.31, and 1.90 dS.m-1 to 1.75,1.78, and 1.74 dS.m-1 for 60 m drain spacing; and 2.21, 2.31, and 1.93 dS.m-1 to 1.80,1.82, and 1.48 dS.m-1 for 80 m drain spacing, respectively, at the end of five years. DRAINMOD-S model was reliably applicable for predicting soil salinity under sub-surface drainage system in arid and semi-arid region of Punjab, India

Computation of subsurface drain spacing in the unsteady conditions using Artificial Neural Networks (ANN)

Artificial neural networks are a tool for modeling of nonlinear systems in various engineering fields. These networks are effective tools for modeling the nonlinear systems. Each artificial neural network includes an input layer, an output layer between which there are one or some hidden layers. In each layer, there are one or several processing elements or neurons. The neurons of the input layer are independent variables of the understudy issue, and the neurons of the output layer are its dependent variables. Artificial neural system, through exerting weight on inputs and by suing an activation function attempts to achieve a desirable output. In this research, in order to calculate the drain spacing in an unsteady state in a region situated in the north east of Ahwaz, Iran with different soil properties and drain spacing, the artificial neural networks have been used. The neurons in the input layer were: Specific yield, hydraulic conductivity, depth of the impermeable layer, height of the water table in the middle of the interval between the drains in two-time steps. The neurons in output layer were drain spacing. The network designed in this research was included a hidden layer with four neurons. The distance of drains computed via this method had a good agreement with real values and had a high precision in compare with other methods.

Modeling Subsurface Drainage in Compacted Cultivated Histosols

Reclaiming histosols in Montéregie region, Québec, Canada, increases peat decomposition and compaction rate and decreases the effectiveness of subsurface drainage. The objective of this paper was to use HYDRUS-2D to model the behavior of subsurface drainage systems, in order to evaluate the compaction effect on drain depth and spacing, and to determine the compact layer thickness and saturated hydraulic conductivities (Ksat) resulting in an improvement of subsurface drainage]. The drainage model was calibrated [Nash-Sutcliffe efficiency coefficient (NSE) = 0.958, percent bias (PBIAS) = −0.57%] using Ksat, meteorological data, and matric potential (h) data measured on the project site from June 10 to July 19, 2017. The calibrated and validated model was used to analyze the variation of h values (Δh in cm d−1) as a function of drain spacing (2–7 m) and drain depth (1 and 1.2 m) and to identify the response surface of Δh to various compact layer thickness and Ksat combinations. The results showed that Δh was on average 58% greater below the compact layer than above it and that reducing drain spacing or increasing drain depth does not improve the drainage rate. The analysis of the compact layer thickness and Ksat effect on Δh showed that for a Δh of 40 cm d−1, Ksat actual values in the two uppermost layers should be multiplied by 50 for compact layer thickness varying from 12 to 35 cm. Water percolation in the soil is reduced by the compact layer. Soil management methods for improving Ksat should therefore be better than deepening the drains or and reducing the spacing.

Evaluation of Parallel Pipe Subsurface Drainage System in a Waterlogged Paddy Field

Inadequate natural drainage facilities and flat lands causes, some of the Cauvery river basin command are suffering waterlogging and alkalinity problems during the canal water supply and period of excess rainfall. Subsurface drainage system is the method to lower the depth to groundwater level below the root zone and creates a favorable environment for crop growth. A study aimed to evaluate the performance of the parallel pipe subsurface system installed in farmers’ field at Sembari village, Lalgudi Taluk, Trichy District, Tamil Nadu in a waterlogged paddy field from October 2020 to February 2021. The field experiment was conducted with the combination of three lateral drain spacing (7.5, 10.0 and 12.5 m) and two drain depths (60 and 80 cm). 63 mm PVC perforated pipes wrapped with coir envelope were laid as lateral drains at a grade 0.3%. Inspection chambers connected with collector drains laid at a grade of 0.6% were used to measure the drain water discharge, observation wells installed midway between lateral pipes drains were used for measuring the depth to groundwater level. Hydraulic properties of soil, depth to water level, discharge collected in drain pipe were used as evaluation parameters. This study revealed that soil hydraulic conductivity had been increased to 30%, pH, EC and ESP has been reduced to 12, 54 and 20%, respectively. The system has performed well to alleviate the waterlogged condition in 7.5 m lateral drain spacing and 80 cm drain depth treatment by observing the higher rate of decrease in depth to water of 0.3 to 0.4 m and a drainage coefficient of 0.069 to 0.29 cm/day.