Browsing by Author "Nandagiri, L."

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A Penman-Monteith evapotranspiration model with bulk surface conductance derived from remotely sensed spatial contextual information
(Taylor and Francis Ltd. michael.wagreich@univie.ac.at, 2020) Shekar N C, S.; Nandagiri, L.
A novel approach involving the use of the contextual information in a scatter plot of Moderate Resolution Imaging Spectrometer (MODIS) derived Land Surface Temperature versus Fraction of Vegetation (LST vs. Fv) has been proposed in this study to obtain pixel-wise values of bulk surface conductance (Gs) for use in the Penman-Monteith (PM) model for latent heat flux (?ET) estimation. Using a general expression for Gs derived by assuming a two-source total ?ET (canopy transpiration plus soil evaporation) approach proposed by previous researchers, minimum and maximum values of Gs for a given region can be inferred from a trapezoidal scatter plot of pixel-wise values of LST and corresponding Fv. Using these as limiting values, Gs values for each pixel can be derived through interpolation and subsequently used with the PM model to estimate ?ET for each pixel. The proposed methodology was implemented in 5 km × 5 km areas surrounding each of four flux towers located in tropical south-east Asia. Using climate data from the tower and derived Gs values the PM model was used to obtain pixel-wise instantaneous ?ET values on six selected dates/times at each tower. Excellent comparisons were obtained between tower measured ?ET and those estimated by the proposed approach for all four flux tower locations (R2 = 0.85–0.96; RMSE = 18.27–33.79 W m–2). Since the LST- Fv trapezoidal method is simple, calibration-free and easy to implement, the proposed methodology has the potential to provide accurate estimates of regional evapotranspiration with minimal data inputs. © 2019, © 2019 Informa UK Limited, trading as Taylor & Francis Group.
An analysis of rainfall variability in Dakshina Kannada District, Karnataka State, was made using historical monthly rainfall data of 31 raingauge stations. For the 25 year period considered, annual and monsoon rainfall totals of individual stations did not deviate much from their mean values, but considerable spatial variations were observed. Analysis of the dependence of spatial variability on station elevation indicated that this factor alone could explain only 55% of the observed variations in annual rainfall. Considering other location dependent parameters, stepwise regression analysis was used to establish relationships between these and rainfall related variables. The regression models so developed were subjected to a validation test and found to comply fairly well. The applicability of the proposed models has been demonstrated by generating an isohyetal map of annual rainfall for the District, using topographical inputs. This map compared fairly well with the isohyetal map drawn using rainfall data. © 1997 Taylor & Francis Group, LLC.
(Location dependent variability of monsoon rainfall in a tropical region) Nandagiri, L.; Thippeswamy, M.; Somanatha, G.S.
1997
Analysis of historical trends in hydrometeorological variables in the upper Cauvery Basin, Karnataka, India
(Indian Academy of Sciences, 2017) Kumar Raju, B.C.; Nandagiri, L.
The present study examines the significance and magnitude of trends in the monthly rainfall, monthly mean maximum and minimum daily temperatures and streamflow in the Upper Cauvery Basin, Karnataka for a 30-year period, i.e. 1981-2010. Using observed data from 33 rain gauges, 6 climate stations and 4 stream gauging sites, statistical parameters -coefficient of variation (CV) and percentage departure have been calculated for average monthly values separately for three decades. As expected, CV of rainfall showed large variations from December to March, while the percentage departure also varies during these months for different decades. Statistically significant trend was observed in maximum temperature for Chikmagalur and Hassan stations. CV of minimum daily temperature showed large variability from November to March for all climate stations and also a significant increasing trend for Hassan and Bengaluru stations, while for Madikeri a decreasing trend was observed with a variation of -0.16°C/year. Not much variation was found for streamflow, except in K. M. Vadi and T. Narasipur gauge sites, which showed significant decreasing trend of -0.778 m3/s/year. Long-range dependence analysis revealed a weak persistence for both rainfall and streamflow of the basin. Results provide information regarding historical climate trends in the Upper Cauvery Basin, which can form the basis for projecting likely future trends and preparing plans for climate change mitigation and adaptation.
Analysis of variability and trends in rainfall over northern Ethiopia
(Springer Verlag service@springer.de, 2016) Kiros, G.; Shetty, A.; Nandagiri, L.
Rainfall is a key component of the hydrological cycle, and its spatiotemporal variability is essential from the both scientific and practical perspectives. This study is focused on analysis of temporal variability and trends in historical rainfall records for stations in the Geba River basin. The Geba catchment is surrounded by the Danakil basin in the east, by the Tekeze River basin in the south, and the Werie River basin in the west which is located in the northern Ethiopia regional state of Tigray between 38° 38? E and 39° 48? E and 13° 18? N and 14° 15? N. The climate over the basin is semi-arid and has large elevation differences varying from 926 to 3301 m above mean sea level. Daily rainfall data of 43 years measured at seven stations in the basin for the period of 1971 to 2013 for annual and seasonal rainfall trends have been processed and used for the analysis. The non-parametric Mann–Kendall test and the Sen’s slope estimator have been used to identify the existence of trends and slope magnitude in rainfall. Results revealed that although there was a mix of positive and negative trends, they were no statistically significant except at one station which showed an increasing trend in annual rainfall. Considering rainfall in different seasons, an increase in rainfall was observed in two stations in the wet season which, however, was not statistically significant. For the remaining stations, a weak decline in wet season rainfall (not statistically significant at 95 % confidence level) for four stations and absence of trend for one station were noticed. Furthermore, no statistically significant trend (positive or negative) was evident for the dry season rainfall. Results of this study may prove useful in the preparation of climate change mitigation and adaptation strategies in rainfed agricultural and water supply systems in the region. © 2016, Saudi Society for Geosciences.
Areal evapotranspiration estimation using several alternative formulations of the CRAE hypothesis
(ASCE, 1997) Nandagiri, L.
Accurate estimation of ET from large irrigated areas is essential for sustainable development of land and water resources. The CRAE hypothesis offers a convenient technique for areal ET estimation using only regularly recorded meteorological data. In this study several alternative models for areal ET are derived from the fundamental CRAE hypothesis and their performances assessed using data of the Everglades Agricultural Area, Florida. Results indicate the feasibility of obtaining acceptable estimates of areal ET from irrigated land using the CRAE concept.
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.
Characterization of climatic parameters in the perspective of irrigated agriculture in Uttar Kannada district of Karnataka, India
(India Meteorological Department mausamps@gmail.com, 2020) Yallurkar, S.; Nayak, S.; Nandagiri, L.
A rainfall and potential evapotranspiration characteristics together determine the agro-meteorological regime of a region and influences decision concerning the magnitudes and timing of irrigation application. In the present study, historical rainfall and climate data pertaining to the study area, Uttar Kannada district, Karnataka, was analyzed with a view to characterizing irrigation water requirements. In addition to rainfall input, an important aspect of the water balance model is the crop evapotranspiration (ETcrop), which is the main factor in determining the irrigation schedule. ETcrop could be estimated by reference evapotranspiration (ET0) and crop coefficient. Atmospheric demand for water is represented by ‘potential evapotranspiration’ (PET) and calculated from climatic variables which is crucial for irrigation planning. It has been reported that the Penman-Monteith method gives more consistently correct ET0 estimates to other ET0 methods. While recognizing the importance of both rainfall and PET, an effective measure is known as the ‘Moisture Availability Index’ (MAI), which is computed as the ratio of 75% dependable rainfall and potential evapotranspiration. An MAI value of 1.00 indicates that dependable precipitation is equal to potential evapotranspiration. An MAI value of 0.33 or less for one month during the crop growing season is considered to be a signal of water deficit resulting reduction in crop yield. The findings of this study on MAI are used to decide the selection of the sowing period of crops so as to avoid water stress during the critical harvesting period. © 2020, India Meteorological Department. All rights reserved.
Characterization of small-scale groundwater irrigation schemes in a humid coastal region of southern India
(2009) Nayak, S.; Nandagiri, L.
Small-scale groundwater irrigation schemes involving large diameter wells are prevalent in the coastal district of Uttara Kannada, Karnataka State, India. A study was conducted to assess the characteristics of these large diameter open wells and the hydraulic properties of shallow aquifers. Field tests were conducted in 19 wells to assess their potential to supply irrigation water requirements of the region. Constant discharge pump tests indicated significant spatial variations in aquifer transmissivity (5.60 to 64.55 m2·day-1) and specific yield (0.063 to 0.95). Low transmissivity values signify poor potential of the aquifer to supply irrigation water needs. Exponential prediction models linking transmissivity and well specific capacity gave a good fit. Implications of spatial variability in aquifer parameters on irrigation development in the region are highlighted.
Characterizing aquifers when using magnetic resonance sounding in a heterogeneous geomagnetic field
(EAGE Publishing BV P.O.Box 18667 Newark NJ 07191-8667, 2011) Vouillamoz, J.M.; Legchenko, A.; Nandagiri, L.
It has previously been reported that the heterogeneity of the geomagnetic field disturbs the currently-measured free induction decay signal of magnetic resonance sounding (MRS). To overcome the limitation of MRS in a non-homogeneous geomagnetic field, we adapted the spin-echo methodology usually used at the laboratory scale and in boreholes. We present examples of measurements carried out in a sandy aquifer in southern India. The 15-25 m thick sand deposit overlays a gneissic basement. Two sources of geomagnetic field heterogeneity have been identified at this site, both affecting the geomagnetic field within the sandy aquifer: the gneissic bedrock and an intruded dyke into the bedrock. Spin-echo and free induction decay signals have been recorded at six locations. We found that the groundwater content, the thickness of the saturated aquifer and its transmissivity calculated with free induction decay measurements are underestimated compared to those derived from spin-echo measurements. The closer to the dyke the higher the underestimation. Time-domain electromagnetic measurements indicate that the aquifer is rather homogeneous at the site scale, as suggested by spin-echo results. We also found that a small heterogeneity of the geomagnetic field can go unnoticed, thus leading to an unknown mis-estimate of aquifer properties when using free induction decay measurements. Thus spin-echo measurements can be used to improve the accuracy of aquifer characterization when using MRS in geological contexts where geomagnetic field heterogeneity exists. © 2010 European Association of Geoscientists & Engineers.
Climate analysis for regional irrigation planning
(2010) Nandagiri, L.; Nayali, S.
Rainfall characteristics and potential evapotranspiration together determine the agro meteorological regime of a region and influence decisions concerning the magnitudes and timing of irrigation applications. In addition to rainfall input, an important aspect of the water balance model is the crop evapotranspiration (ETcrop), which is a main factor in determining irrigation schedule. The procedure for estimation of ET rates from agricultural crops is well established and involves as a first step, computation of reference crop evapotranspiration (ETcrop) using regular climatologically recorded data. ETcrop could be estimated by reference evapotranspiration (ET) and crop coefficient. ‘Moisture Availability Index’ (MAI), which is computed as the ratio of 75% dependable rainfall and potential evapotranspiration is used as an index to indicate dry and wet periods. An MAI value of 1.00 indicates that dependable precipitation equals potential evapotranspiration. A value of MAI of 0.33 or less for one month during the crop-growing season is considered to be a signal of water deficit, causing crop production to fall below an economic level. Obtained information on MAI is used to decide the selection of sowing period of crops so as to avoid water stress during crucial harvesting period. © 2010 Taylor & Francis Group, LLC.
Developing regression models for predicting pan evaporation from climatic data - A comparison of multiple least-squares, principal components, and partial least-squares approaches
(2007) Kovoor, G.M.; Nandagiri, L.
Regression models for predicting daily pan evaporation depths from climatic data were developed using three multivariate approaches: multiple least-squares regression (MLR), principal components regression (PCR), and partial least-squares (PLS) regression. The objective was to compare the prediction accuracies of regression models developed by these three approaches using historical climatic datasets of four Indian sites that are located in distinctly different climatic regimes. In all cases (three approaches applied to four climatic datasets), regression models were developed using a part of the data and subsequently validated with the remaining data. Results indicated that although performances of the regression models varied from one climate to another, more or less similar prediction accuracies were obtained by all three approaches, and it was difficult to identify the best approach based on performance statistics. However, the final forms of the regression models developed by the three approaches differed substantially from one another. In all cases, the models derived using PLS contained the smallest number of predictor variables; between two to three out of a possible maximum of six predictor variables. The MLR approach yielded models with three to six predictor variables, and PCR models included all six predictor variables. This implies that the PLS regression models are the most parsimonious in terms of input data required for estimating epan from climate variables, and yet yield predictions that are almost as accurate as the more data-intensive MLR and PCR models. © 2007 ASCE.
Development of daily gridded Penman-Monteith reference crop evapotranspiration data for Karnataka State, India
(Taylor and Francis Ltd., 2024) Niranjan, S.; Nandagiri, L.
Reference crop evapotranspiration (ET0) estimates are often unavailable at fine spatial resolutions due to the lack of dense climatic networks. The present study was taken up to develop a methodology for obtaining a gridded Penman-Monteith (PM) ET0 dataset for Karnataka State, India, through spatial interpolation of estimates obtained at climate stations. Three interpolation techniques, Inverse Distance Weighted (IDW), Kriging, and Point-Based Sentinel Hospitals Area Distance (P-BSHADE), were employed to derive PM ET0 estimates. Considering the historical climate records of 67 stations located in Karnataka State for the period of 2006–2016, the interpolation methodologies were evaluated using a cross-validation procedure. Results showed that the performance of IDW was better with significant error reduction at validation sites. Subsequently, the IDW algorithm was used to derive daily PM ET0 values at 0.25° × 0.25° grids over the Karnataka State, India. Finally, the comparative analysis of developed PM ET0 gridded data product against three global ET0 products indicated the developed gridded ET0 to be most accurate across different agroclimatic zones. Web links of the developed product have been created in an effort to share the data on ET0, which is a critical input in a variety of studies in earth sciences. © 2023 Indian Society for Hydraulics.
Effect of local calibration on the performance of the hargreaves reference crop evapotranspiration equation
(IWA Publishing, 2021) Niranjan, S.; Nandagiri, L.
Obtaining accurate estimates of reference crop evapotranspiration (ET0) using limited climatic inputs is essential in data-short situations where the preferred FAO-56 Penman–Monteith (PM) equation cannot be implemented. Among several available for ET0 estimation, the empirical temperature-based Hargreaves–Samani (HG) equation remains a popular alternative. However, accurate HG estimates can be obtained by local calibration and replacing the mean daily temperature with the effective daily temperature. Therefore, the present study was taken up to evaluate the effects of site-specific calibration of model parameters and the use of effective air temperature on the accuracy of ET0 estimates by the HG model. For this purpose, climate records for the historical period 2006–2016 of 67 stations located across 10 agro-climatic zones of Karnataka State, India, were used and the analysis was carried out using a monthly time step. Calibration and statistical performance evaluation was performed using FAO-56 PM ET0 estimates as a reference. Overall results showed significant improvement in HG estimates across all zones with the use of locally calibrated parameters, whereas the use of effective air temperature did not lead to any significant gain in prediction accuracies. The derived information on the spatial distribution of calibrated parameters will help obtain accurate ET0 estimates with only air temperature inputs. © 2021 The Authors.
Evaluating uncertainty of the soil and water assessment tool (SWAT) model in the upper cauvery basin, Karnataka, India
(CAFET INNOVA Technical Society 1-2-18/103, Mohini Mansion, Gagan Mahal Road, Domalguda, Hyderabad 500029, 2015) Kumar Raju, B.C.; Nandagiri, L.
Quantification of uncertainties associated with hydrological models are essential for accurate assessment of water balance components and optimal planning and management of water and land resources at basin-scale. The present study was taken up to evaluate the uncertainties associated with the Soil and Water Assessment Tool (SWAT) model using for two different techniques: i) Generalized Likelihood Uncertainty Estimation (GLUE) and ii) Sequential Uncertainty Fitting (SUFI-2) techniques. The study was carried out in the Upper Cauvery River basin (36,682 km2) located in the humid to sub-humid region of Karnataka State, India. The calibration of the model was carried out using the Nash – Sutcliffe (NS) coefficient as the objective function for both GLUE and SUFI-2 techniques. The P-factor was 67% and 71% of observed streamflow data bracketed by the 95% prediction uncertainty (95PPU) for GLUE and SUFI-2 respectively during calibration period and corresponding values of 54% and 61% during validation period. Overall results indicate the applicability of SWAT model with moderate levels of uncertainty in large basins located in the humid tropics. The calibrated SWAT model can be used for assessment of water balance components and land use management scenarios in the Upper Cauvery Basin. © 2015 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.
Extraction of Nonlinear Trends in Time Series of Rainfall Using Singular Spectrum Analysis
(American Society of Civil Engineers (ASCE) onlinejls@asce.org, 2020) Aswathaiah, U.; Nandagiri, L.
Characterization of nonlinear trends in time series of hydroclimatic variables exhibiting nonstationarity is necessary for more realistic projections of climate change and for optimal design of hydraulic structures. The present study was conducted to demonstrate the applicability of a novel Monte-Carlo-based singular spectrum analysis (SSA) to characterize nonlinear trends in historical time series of rainfall characteristics. Long-term (1960-2015) rainfall records for 17 gauges located in the Malaprabha River Basin, India, were used to analyze spatiotemporal variabilities of trends in rainfall totals and number of rainy days for annual and seasonal time periods. While the traditional Sen's Slope and Mann-Kendall (MK) trend tests indicated statistically nonsignificant decreasing monotonic trends at most gauge stations, SSA revealed the existence of steep nonlinear trends and distinct change points in the direction of the trend over the period of record for both rainfall and rainy days. Results of this study demonstrate the potential for SSA to extract crucial information on the trajectories of nonlinear trends and change points in time series of hydroclimatic variables that exhibit nonstationarity. © 2020 American Society of Civil Engineers.
Groundwater prospective mapping: Remote sensing and a GIS based index model approach
(2008) Shetty, A.; Nandagiri, L.; Padmini, R.
The present study is concerned with the development and test of an integrated remote sensing and GIS based methodology for identification of groundwater potential areas in a humid tropical river basin. Indian Remote Sensing Satellite (IRS 1C-LISS-III) data along with other collateral data such as existing maps and field observations was utilized to extract information on the hydro-geomorphic features of the terrain. The study involves two components: (a) demarcation of groundwater potential zones (b) validation of sites with yield data. In order to demarcate potential groundwater zones, six pertinent thematic layers were integrated and assigned appropriate rankings. Layers considered were: geology, geomorphology, drainage density, slope, rainfall with infiltration factor and land cover map. The layer parameters were also rated according to their importance relative to other classes in the same theme. All the layers were superimposed and analyzed in ARC GISÂ® environment. A linear additive model based on the DRASTIC model concept was used to find the groundwater potential index (GPI). The map comprised of six categories of groundwater yield. To carry out more focused investigations on the potential zones, lineament maps were superimposed over it. The validity of different potential zones identified using the GIS-based model was compared with available borewell yield data and found to be in good agreement. The map generated can be used in future as a preliminary screening tool in selecting well sites and as a basic tool in land use planning for groundwater protection. Â© 2008 SPIE.
Historical development of irrigated agriculture under the Malaprabha Project, Karnataka, India
(Indian Academy of Sciences, 2020) Aswathaiah, U.; Nandagiri, L.
The present study analyses the historical development of irrigated agriculture in the command area of the Malaprabha irrigation project located in a semi-arid region of Karnataka, India. Considering the historical period from 1965 to 2014, spatio-temporal changes in irrigated area, cropping patterns, crop and irrigation water requirements using CROPWAT model and sources of irrigation water were characterized relative to the pre-project period at decadal time-step. Overall results indicate an increase in irrigated area, depar-ture from the planned cropping pattern and a shift towards cultivation of water-intensive cash crops, canal releases not conforming to estimated irrigation water requirements and an increase in groundwater-based irrigation in the command area of the project. The findings of this study can be used to formulate more effective management strategies to improve the efficiency of the project and promote sustainable development of natural resources. © 2020. All rights reserved.
Latent heat flux estimation using trapezoidal relationship between MODIS land surface temperature and fraction of vegetation-application and validation in a humid tropical region
(Taylor and Francis Ltd., 2014) Laxmi, K.; Nandagiri, L.
The present study was taken up with the objective of developing a methodology for estimation of actual evapotranspiration (AET) using only satellite data. Accordingly, an algorithm based on the popular Priestley-Taylor method was developed. While previous studies have assumed a triangular relationship between land surface temperature (LST) and fraction of vegetation (FV) to calculate the Priestley-Taylor parameter (?), a trapezoidal relationship was adopted in the present study to enable applications in forested regions in the humid tropics. The developed algorithm was applied to the humid tropical Mae Klong region, Thailand, and latent heat flux (ET) estimates were validated with measurements made at a flux tower located at the centre of the region. Moderate Resolution Imaging Spectroradiometer (MODIS) remote sensing satellite data products corresponding to the study area were used to derive various inputs required by the algorithm. Comparison of estimated and measured fluxes on five cloud-free days in 2003 yielded root mean square error (RMSE) of 64.73 W m-2 which reduced to 18.65 W m-2 when one day was treated as an outlier. The methodology developed in this study derived inputs only from satellite imagery and provided reasonably accurate estimates of latent heat flux at a humid tropical location. © 2014 Taylor & Francis.
Modeling actual evapotranspiration using the advection aridity model
(Blue Eyes Intelligence Engineering and Sciences Publication, 2019) Ananya, S.G.; Nandagiri, L.
Evapotranspiration is a major process in the hydrological cycle. Between 40 to 60% of precipitation is returned back to the atmosphere in the form of evapotranspiration. Therefore, estimation of Actual Evapotranspiration (AET) is important in studies related to hydrology, agriculture and climate. However, due to the fact that calculation of AET using conventional methods require data pertaining to climate, vegetation/crop and soil moisture levels, estimation of spatial AET becomes a very tedious task. The Complementary Relationship Areal Evapotranspiration (CRAE) hypothesis has been proposed as a simpler alternative to estimate AET from large spatial domains using only routinely observed meteorological data thereby circumventing the need for data on soil-vegetation. The objective of the present work was to apply the CRAE hypothesis in Karnataka State, India and evaluate the accuracy of estimates using MODIS satellite-derived AET estimates. The Advection Aridity (AA) model which is based on the CRAE hypothesis was chosen to estimate AET using historical climate records of the Afzalpur and Hungund stations. The AA model uses the Penman equation to estimate the Potential ET and the Priestley-Taylor equation to estimate Wet Environment ET which are needed to estimate AET. Accuracy of AET values obtained from the AA model were validated using the MODIS MOD16A2 evapotranspiration product, which provides an 8-day composite AET estimate at 500 m resolution. AET estimated by the AA model compared favorably with MOD16A2 with the average Coefficient of determination (R2)for the two stations being 0.8095. While the results of this study have shown that the AA model provides reasonably accurate AET estimates with minimum data, further studies need to be carried out to improve the accuracy through local calibration of parameters. ©BEIESP.
Modelling soil moisture under different land covers in a sub-humid environment of Western Ghats, India
(Indian Academy of Sciences, 2011) Venkatesh, B.; Nandagiri, L.; Purandara, B.K.; Reddy, V.B.
The objective of this study is to apply and test a simple parametric water balance model for prediction of soil moisture regime in the presence of vegetation. The intention was to evaluate the differences in model parameterization and performance when applied to small watersheds under three different types of land covers (Acacia, degraded forest and natural forest). The watersheds selected for this purpose are located in the sub-humid climate within the Western Ghats, Karnataka, India. Model calibration and validation were performed using a dataset comprising depth-averaged soil moisture content measurements made at weekly time steps from October 2004 to December 2008. In addition to this, a sensitivity analysis was carried out with respect to the water-holding capacity of the soils with the aim of explaining the suitability and adaptation of exotic vegetation types under the prevailing climatic conditions. Results indicated reasonably good performance of the model in simulating the pattern and magnitude of weekly average soil moisture content in 150 cm deep soil layer under all three land covers. This study demonstrates that a simple, robust and parametrically parsimonious model is capable of simulating the temporal dynamics of soil moisture content under distinctly different land covers. Also, results of sensitivity analysis revealed that exotic plant species such as Acacia have adapted themselves effectively to the local climate. © Indian Academy of Sciences.