Bhabagrahi Sahoo

Standardization of Reference Evapotranspiration Models for a Subhumid Valley Rangeland in the Eastern Himalayas

AbstractFor efficient irrigation water management and hydro-meteorological studies at both the field and catchment scales, a need exists to evaluate the existing evapotranspiration (ET) estimation methods under varied physiographical and data availability conditions. In this study, using the FAO-56 Penman-Monteith model as the benchmark model, a total of 16 various ET estimation methods were evaluated using both the continuous daily time series and average time series weather data of a subhumid valley cultivated rangeland in the eastern Indian Himalayas. The results revealed that some pan evaporation models have restricted performances. Consequently, for an improved performance, all of these models were standardized using a genetic algorithm–based linear corrector transformation model. Almost all of the models performed reasonably well when using the average daily time series data. Furthermore, the trend analysis of reference ET showed an increasing trend during the months of February to July, including O...

Multilinear Muskingum Method for Stage-Hydrograph Routing in Compound Channels

A multilinear stage-hydrograph routing method based on time distribution scheme is analyzed. The framework of the multilinear method is based on the Muskingum-type routing method, which is used as the linear submodel. The proposed method can implicitly model the nonlinear dynamics of the flood wave propagation by varying the model parameters at each routing time step. The suitability of this flood routing method is verified using a set of laboratory experimental data and the field data of the Tiber River in central Italy.

Field Application of the Multilinear Muskingum Discharge Routing Method

To implicitly model the nonlinear dynamics of flood wave propagation in rivers with floodplains, a multilinear discharge-hydrograph routing method based on time distribution scheme is proposed. The framework of this method is based on the variable parameter Muskingum-type routing method, which is used as the linear sub-model. The applicability limit and suitability of this flood routing method is verified using numerical experiments and field data, respectively.

Rating Curve Development at Ungauged River Sites using Variable Parameter Muskingum Discharge Routing Method

A physically based simplified discharge routing method, namely, the variable parameter Muskingum discharge-hydrograph (VPMD) routing method, having the capability of estimating the stage hydrographs simultaneously in channels with floodplains is presented herein. The upstream discharge hydrograph is routed using this VPMD method in different two-stage symmetrical trapezoidal compound cross section channel reaches. The performance of the VPMD method is evaluated by numerical experiments using the benchmark MIKE11 hydrodynamic model and the field data of the Tiber River in central Italy. The proposed method is capable of accurately routing the discharge hydrographs, corresponding stage hydrographs and synthesizing the normal rating curves at any downstream ungauged river site which is not affected by any downstream effects. This study can be helpful for various planning and management of river water resources in both the diagnostic and prognostic modes.

Evaluation of variable-infiltration capacity model and MODIS-terra satellite-derived grid-scale evapotranspiration estimates in a river basin with tropical monsoon-type climatology

AbstractWith the limited availability of meteorological variables in many remote areas, estimation of evapotranspiration (ET) at different spatiotemporal scales for efficient irrigation water manag...

Estimating Floods from an Ungauged River Basin Using GIUH-Based Nash Model

Among the existing mesoscale rainfall-runoff models, the geomorphological instantaneous unit hydrograph (GIUH) models can predict the streamflow reasonably well in less data availability conditions using the measurable basin geomorphology. In light of this, the rainfall-runoff transformation process of the Baitarani River Basin at Anandapur in eastern India was studied herein using the GIUH-based Nash model. In this model, the gamma function of the Nash model is approximated that does not need the computation of either the complete or incomplete gamma functions. To evaluate the efficacy of this model, four performance evaluation measures of Nash–Sutcliffe efficiency, percentage error in volume, percentage error in peak, and percentage error in time to peak are used. The results reveal that the GIUH-based Nash model performs with the average Nash–Sutcliffe model efficiency of 87.21(±8.05) % with overprediction of the runoff volume by 29.91(±18.76) %. However, this model could estimate the runoff peak more accurately with an average peak error of 3.86 (±2.50) % having an average time to peak error of 2.08(±4.17) %. Hence, overall, the GIUH-based Nash model has the capability of estimating the basin-scale runoff reasonably well.

Impact of LULC change on the runoff, base flow and evapotranspiration dynamics in eastern Indian river basins during 1985–2005 using variable infiltration capacity approach

As a catchment phenomenon, land use and land cover change (LULCC) has a great role in influencing the hydrological cycle. In this study, decadal LULC maps of 1985, 1995, 2005 and predicted-2025 of the Subarnarekha, Brahmani, Baitarani, Mahanadi and Nagavali River basins of eastern India were analyzed in the framework of the variable infiltration capacity (VIC) macro scale hydrologic model to estimate their relative consequences. The model simulation showed a decrease in ET with 0.0276% during 1985–1995, but a slight increase with 0.0097% during 1995–2005. Conversely, runoff and base flow showed an overall increasing trend with 0.0319 and 0.0041% respectively during 1985–1995. In response to the predicted LULC in 2025, the VIC model simulation estimated reduction of ET with 0.0851% with an increase of runoff by 0.051%. Among the vegetation parameters, leaf area index (LAI) emerged as the most sensitive one to alter the simulated water balance. LULC alterations via deforestation, urbanization, cropland expansions led to reduced canopy cover for interception and transpiration that in turn contributed to overall decrease in ET and increase in runoff and base flow. This study reiterates changes in the hydrology due to LULCC, thereby providing useful inputs for integrated water resources management in the principle of sustained ecology.

Modelling the variability of hillslope drainage using grid-based hillslope width function estimation algorithm

Abstract Due to the lack of observed groundwater table data and micro-scale topography of the hillslopes constituting a watershed, quantification of subsurface flow using the existing models becomes very difficult. In this context, a low dimensional hillslope storage dynamic model has been developed in this study to represent the physical behaviour of the watershed at the hillslope-scale. The topographic control of the watershed has been described in terms of the hillslope width function (HWF) involving the D8 algorithm-based stream network delineation. Subsequently, to simplify the complex spatial variability of HWF, the distribution functions of exponential, Fourier and Gaussian are fitted and their implications on the variability of the subsurface drainage are quantified in a real Indian watershed. The results reveal that the Gaussian distribution function estimates the subsurface flow very well as compared to the other functions.

Modelling the dynamics of evapotranspiration using Variable Infiltration Capacity model and regionally calibrated Hargreaves approach

Computation of reference evapotranspiration (ETO) at different spatiotemporal scales is constrained by limited in situ meteorological data availability which, in turn, led to alternate ET estimation methods using the commonly available meteorological data of maximum and minimum temperatures. In this study, the Hargreaves–Samani model and the water budget approach of the Variable Infiltration Capacity (VIC-3L) land surface model was evaluated for grid-scale actual ET estimation using the benchmark FAO-56 Penman–Monteith (PM) equation and crop coefficient relationships. These approaches were field-tested in the Kangsabati River basin in eastern India, a tropical monsoon-type climate region with dominant paddy land uses. The results revealed that the VIC model could estimate the grid-scale ET reasonably well; however, the corresponding estimates by the Hargreaves method were highly overestimated. To enhance the field applicability of the Hargreaves method for data-scarce regions, this method was coupled with a genetic algorithm-based bias correction approach that improved the Nash–Sutcliffe efficiency significantly. Hence, this study reveals that there is a need for regional-scale standardization of the Hargreaves ET estimates using the FAO-56 PM, lysimeter data or the VIC-3L model.