Performance of radial point interpolation method in solving kinematic wave equation for hydrologic modelling

This paper presents the solution of the kinematic wave equation using a meshless radial point interpolation method (RPIM). The partial differential equation is discretized using a Galerkin weighted residual method employing RPIM shape functions. A forward difference scheme is used for temporal discretization, while the direct substitution method is employed to solve the nonlinear system at each time step. The formulation is validated against solutions from conventional numerical techniques and physical observation. In all cases, excellent agreements are achieved and hence the validation of the proposed formulation. Optimum values of the multi-quadrics shape parameters were then determined before the assessment of the performance of the method. Based on the convergence rate, it has been shown that the proposed method performs better than the finite difference method and equivalent to the finite element method. This highlights the potential of RPIM as an alternative method for hydrologic modeling

Performance of vapour pressure models in the computation of vapour pressure and evapotranspiration in ABHA, ASIR region, Saudi Arabia

The FAO-56 Penman-Monteith model is recognized as the standard method for estimating reference evapotranspiration (ETo) which requires daily meteorological data as inputs. Among all input data, vapour pressure deficit (VPD) is one of the critical parameter that drives evapotranspiration (ETo), and is of fundamental importance in crop models. In this study effort has been made to compare six vapour pressure models during four seasons. Three vapour pressure models (Models 1–3) selected as mentioned in Irrigation and Drainage Paper-56 of the Food and Agriculture Organization (FAO-56) and Models 4-6 has been selected from literature survey. Model 1, which uses daily maximum and minimum temperature, relative humidity (RH), is the preferred method to estimate actual air pressure (AE) hence it is used as standard for comparing other models. The effectiveness of vapour pressure models were measured by statistical tools and ranked according to Global Performance Indicator (GPI) where higher value of GPI represent best model. The ranking order using GPI shows that Model 5 resulted in best estimation capability with a GPI of 2.77. Moreover, the effect of variation in wind speed on the performance of the vapour pressure models in ETo estimation is also assessed

Calibration and validation of reference evapotranspiration models in semi-arid conditions

Reference evapotranspiration (ETo) is an important parameter for climatological, hydrological and agricultural management. The FAO56 Penman-Monteith (FAO56-PM) model is one of the most accurate models. But it needs a detailed climate dataset from weather stations. Therefore, empirical reference evapotranspiration models (ETo) that need a reduced set of climate data can become an alternative approach. In this study, nine different evapotranspiration models were calibrated for the 1978-2000 period and validated based on the period between 2001-2017 with respect to standard FAO56-PM method based on the real climatic data obtained from Aseer metrological department, Saudi Arabia. The ranking of all the evaluated models based on the multi-criteria decision making was done in order to get the best alternative to the FAO56-PM Model. The result showed that Mahringer and Trabert models are the most appropriate with RMSE values of 2.13 mm/day and 2.47 mm/day, respectively and the value of percent error were 77.27% and 89.43%, respectively. Moreover, the values of mean bias error were found to be-2.03 mm/day and-2.35 mm/day, respectively. The calibration and validation of different ETo equations tend to increase their performance. Thus, the validated evapotranspiration model that used less climatic parameters could predict the ETo condition accurately for any region

Performance evaluation of mass transfer-based method using global performance index in semi-arid region Saudi Arabia

The standard method for the estimation of reference evapotranspiration (ETo) is FAO-Penman-Monteith(FAO56-PM). However, it requires various climatic parameters which are often hard to achieve due to various reason. In order to bridge this gap an alternative equation has to be find out. The main aim of this research work was to assess the performance of the various mass transfer-based method with respect to standard FAO56-PM. Daily meteorological data from 1980 to 2018 has been used to compute reference evapotranspiration. Daily ETo values were computed. Among the computed values 70% of them were used to calibrate the mass transfer equations under study and remaining 30 % data were used to validate the calibrated equation against the standard method. The calibrated models were analysed and compared using statistical tools and ranked using Global Performance Indicator where a higher value represented a model’s better performance. The models were then arranged using GPI and it was found that Albrecht model resulted in best estimation capability. The results of this study could be used by the water management system, crop cultivators, crop advisors, researchers and students from universities and research centres. Moreover, it is beneficial for the decision maker in the vast field of agriculture, hydrology and environment

Evaluation of mass transfer evapotranspiration models under semiarid conditions using MCDM approach

The selection of suitable reference evapotranspiration (ETo) models in case of climatic data scarcity is a challenging task as it plays a pivotal role in agriculture and water resource management. Therefore, the research work deals with selecting the appropriate mass transfer reference evapotranspiration model using multi criteria decision technique (MCDM) in a semi-arid region of the southern part of Kingdom of Saudi Arabia i.e., Abha. The ten mass transfer methods with ten criteria (statistical indices) using available weather parameters from 1980 to 2018 have been illustrated in this study. Models were calibrated (1980-2006) and validated for the period (2007-2018). The objective weight was computed by criteria importance through inter criteria correlation (CRITIC) method and performance score by weighted sum model (WSM), weighted product model (WPM), weighted aggregates sum product assessment (WASPAS) and evaluation based on distance from average solution (EDAS) methods which in turn rank the evapotranspiration method. The rankings obtained from MCDM techniques were validated with ranking by GPI method using spearman ranking coefficient. The result from MCDM shows that Saif model is the best model and that also GPI yielded same result. The methodology applied in this study can be adopted in any other region which in turns proved to be beneficial for crop cultivators, crop advisors, researchers, and water resource management

Meshless point interpolation formulation of kinematic wave equation for flood routing

This study presents the meshless Point Interpolation Method (PIM) formulation to solve kinematic wave equation for flood routing. It details on Galerkin residual method employing PIM shape functions in discretizing the unsteady partial differential equation. Two nonlinear solvers are considered; Picard and Newton-Raphson. The formulation are verified against both hypothetical data obtained from conventional numerical methods (finite difference and finite element method) and gauged data obtained from an actual river. Close agreements are obtained between the proposed PIM formulation and the conventional methods thus highlight the potential of PIM as an alternative numerical method in the field of hydrologic modelling