- “A unified depth-averaged approach for integrated modelling of surface and subsurface flow systems” by Alok Kumar in Journal of Hydrology Advisor: Dr. Gourabananda Pahar
- “Spatio-temporal variability of soil moisture in a cropped agricultural plot within the Ganga Basin, India” by Ephrem Yetbarek Gedilu published in Agricultural Water Management Advisor: Dr. Richa Ojha
- “Numerical investigation of streamtube approach to model flow in heterogeneous unsaturated sandy soils” by Saurabh Kumar and Ephrem Yetbarek Gedilu published in Journal of Hydrology Advisor: Dr. Richa Ojha
- “A unified depth-averaged approach for integrated modelling of surface and subsurface flow systems” by Alok Kumar in Journal of Hydrology
Advisor: Dr. Gourabananda Pahar
Integrated surface and subsurface flow system
A two-dimensional depth-averaged continuum framework is developed for simulating the interaction of flows outside and within porous media. A unique set of generalized equations applicable to both surface and subsurface systems is derived originating from conservation laws of microscopic variables with first volume-averaging and then integrating vertically. The model is free of ad-hoc coupling as interface conditions are satisfied implicitly owing to the generalized nature of the governing equations. The set of depth-integrated equations (unconditionally hyperbolic) is resolved by employing a Total-Variation-Diminishing MacCormack scheme. The developed model is validated with four one-dimensional experimental test-cases (containing both Darcy and non-Darcy regimes) and applied to a demonstrative two-dimensional scenario having various interface conditions. Results obtained from the proposed framework highlights the potential applicability of the generalized model for diverse time-scales and vertical/ sloping interface conditions.
Read more at:
https://www.sciencedirect.com/science/article/pii/S002216942030799X#f0005
- “Spatio-temporal variability of soil moisture in a cropped agricultural plot within the Ganga Basin, India” by Ephrem Yetbarek Gedilu published in Agricultural Water Management
Advisor: Dr. Richa Ojha
Experimental agricultural plot at IIT Kanpur
Soil moisture dynamics in response to rainfall and irrigation events were examined using data obtained from continuous point measurements carried out under rice and wheat crops for an agricultural plot located within the Ganga Basin, India. Soil moisture data were collected using SM100 and SMEC300 sensors at 18 subplots and at four different depths (0−80 cm) during the period from 5 August 2018 to 31 March 2019. Soil moisture was decomposed into temporal mean and temporal anomalies components, and its variability was characterized considering both absolute soil moisture and temporal anomalies. They exhibited similar patterns at all the depths under rice crop cover. However, it varies with depth under wheat crop cover due to periodic wetting and drying conditions and temporally variable atmospheric demand. Similarly, the spatial variance of absolute soil moisture was decomposed into time-invariant and time-variant components. The results revealed that the time-invariant component contribution was dominant at all the depths (72.49–101.46 %) and the contribution of each component varies with soil wetness and land cover. In addition, temporal stability analysis of soil moisture was carried out. It was observed that the spatial pattern at surface depth cannot be preserved for subsurface depths, and similar subplots were found to be temporally stable at the surface and bottom depths under different crop covers. The results are expected to help improve the understanding of the nature of soil water dynamics in agricultural fields.
Read more at:
https://www.sciencedirect.com/science/article/pii/S0022169420307101
- “Numerical investigation of streamtube approach to model flow in heterogeneous unsaturated sandy soils” by Saurabh Kumar and Ephrem Yetbarek Gedilu published in Journal of Hydrology
Advisor: Dr. Richa Ojha
This study investigates the prediction ability of streamtube approach to model flow in heterogeneous unsaturated sandy soils under a rainfall event at a plot scale. Towards this aim, a numerical model for solving 3-D Richards’s equation was developed and verified for 1-D and 3-D cases. Turning band method was used to generate the random field of soil hydraulic parameters. The 3-D soil field heterogeneity was represented by considering variation in both van Genuchten parameter (α) and Ks. For streamtube models, two cases of heterogeneity were investigated: i) variability in Ks only, and ii) variability in both Ks and α. Both the parameters were assumed to follow a log-normal distribution. For different boundary conditions at the soil surface and varying soil heterogeneity, the average Darcy's flux and mean field-scale soil moisture obtained using streamtube approach were compared with 3-D numerical solutions. The results identify that for high recharge rate at the soil surface, streamtube model is a good approximation of the 3-D heterogeneous soil field, and the average difference in mean soil moisture obtained from 3-D model and streamtube based 1-D model was below 10% when variability in both Ks and α was considered for all timesteps. The inclusion of variability in α leads to improvement in prediction capability of streamtube model. Further, regression equations were developed that can be utilized to predict the mean field soil moisture for heterogeneous 3-D sandy soil fields given the mean field soil moisture obtained from streamtube approach for both the cases. The regressions equations follow exponential model for case-1 and linear model for case-2 with R2 values 0.80 and 0.99, respectively. The developed equations can be reliably used to predict mean field soil moisture for heterogeneous sandy soil fields.
- “Diffusion Wave Approximation of Depth-Averaged Flow Interaction with Porous Media” by Naveed Ul Hassan Bhat published in Journal of Hydrologic Engineering
Advisor: Dr. Gourabananda Pahar
A two-dimensional diffusive wave framework is proposed for modeling interaction between flow through and outside porous media. The depth-integrated parabolic model was developed with an assumption of zero temporal/convective accelerations, making it appropriate for field-scale simulations. The effects of bed shear arising from the bathymetry, roughness, and properties of granular media are consolidated into a single hydraulic diffusivity coefficient. The equation is resolved in a structured finite-volume grid with implicit time stepping. The proposed framework was validated with a standard analytical solution and small-scale experimental results. A synthetic test case containing irregular ground surface demonstrated the capability of the proposed model for real-time simulation.
Read more at:
https://ascelibrary.org/doi/abs/10.1061/%28ASCE%29HE.1943-5584.0002028
