Faculty Publications

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Author: search.filters.author.Nandagiri, L.Subject: search.filters.subject.watershed

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    Soil water fluxes under different land covers - A case study from Western Ghats, India
    (2011) Venkatesh, B.; Nandagiri, L.; Purandara, B.K.
    Knowledge of soil water fluxes is essential in hydrologic studies related to infiltration, runoff, ground water recharge and water uptake by vegetation. Previous studies have investigated the role played by soil and atmospheric factors on soil water fluxes in the unsaturated zone, but few studies have investigated the role played by vegetation or land cover. The present study was taken up understand the effect of land cover on soil water fluxes through long-term field measurements made in three experimental watersheds located in Western Ghats mountain ranges covering a portion of Uttara Kannada District, Karnataka State, India. Soil and climatic conditions were the same for the selected watersheds but they possessed different land covers - natural forest, degraded forest and acacia plantation. In addition to measurements of hydro-meteorological parameters, soil matric potential measurements were made at 4 locations in each of the watersheds up to a depth of 150 cm at an interval of 50 cm. Measurements were made for a period of 2 years (2007-2008) at weekly time intervals Depth-wise soil matric potential measurements were used to estimate soil water fluxes using Darcy's equation for unsaturated porous media. The estimated values of soil water fluxes were analyzed for their temporal distribution and stability. Results indicated that there is an improvement in soil moisture holding under the acacia plantation in comparison to degraded watershed. The estimated deviation of the soil water flux from the field average values indicate that the points located on milder slopes are representative of watershed mean soil water flux. Results also indicated the temporal persistence of soil water fluxes. © 2011 CAFET-INNOVA technical society. All right reserved.
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    Assessment of variable source area hydrological models in humid tropical watersheds
    (Taylor and Francis Ltd. michael.wagreich@univie.ac.at, 2018) Kumar Raju, B.C.K.; Nandagiri, L.
    The objective of this study was to compare the performances of hydrological models that incorporate the Variable Source Area (VSA) mechanism of runoff generation with that of the Soil and Water Assessment Tool (SWAT), which uses the infiltration-excess mechanism. One of the VSA-based model used, SWAT–VSA, has been proposed as a re-conceptualization of the SWAT and uses a topography-based wetness index to identify source areas. In this study, the topography-based wetness index was replaced with a Modified Normalized Difference Water Index (MNDWI) derived from satellite imagery resulting in the SWAT–MNDWI model. Model performances were evaluated through their application in two humid tropical watersheds (Hemavathi–2974 km2; Harangi–538.8 km2) located in the Upper Cauvery River Basin, India. Using relevant data inputs, the three models were applied separately to both watersheds. Models were calibrated for the historical period 2000–2003 and validated for the period 2004–2006 using observed daily observed streamflow records at the watershed outlets. Overall, the SWAT–MNDWI model was the best one in simulating daily streamflow with Nash–Sutcliffe efficiency of 0.85, coefficient of determination of 0.88, percentage bias of 13.2% and root mean square error of 37.48 m3/s for the Hemavathi watershed and corresponding values of 0.88, 0.88, 1.09% and 16.67 m3/s for the Harangi watershed. The spatial patterns of surface runoff generation were similar for the SWAT–VSA and SWAT–MNDWI models, but completely different for the SWAT model. Overall results have demonstrated that models incorporating VSA hydrology, and in particular the proposed SWAT–MNDWI model, provide accurate and convenient tools for distributed hydrologic modelling in humid tropical watersheds. © 2017 International Association for Hydro-Environment Engineering and Research.