Mesoscale Hydrologic Model Research Articles

Predictions in a data-sparse region using a regionalized grid-based hydrologic model driven by remotely sensed data

The goal of this study was to assess the feasibility of using Tropical Rainfall Measuring Mission (TRMM) and Moderate Resolution Imaging Spectroradiometer (MODIS) products to drive a mesoscale hydrologic model (mHM) in a poorly gauged basin. Other remotely sensed products such as LandSat and Shuttle Radar Topography Mission (SRTM) were also used to complement the local geoinformation. For this purpose, three data blending techniques that combine satellite with in situ observations were implemented and evaluated in the Mod basin (512 km2) in India. The climate of the basin is semi-arid and monsoon-dominated. The rainfall gauging network comprised six stations with daily records spanning 9 years. Daily discharge time series was only 4 years long and incomplete. Lumped and distributed versions of mHM were evaluated. Parameters of the lumped version were obtained through calibration. A multiscale regionalization technique was used to parameterize the distributed version using global parameters from other gauged basins. Both mHM versions were evaluated during six monsoon seasons. Results of numerical experiments indicated that driving mHM with satellite-based products is possible and promising. The distributed model with regionalized parameters was at least 20% more efficient than that of its lumped version. Initialization conditions must be carefully considered when the model is only driven by remotely sensed inputs.

The effects of spatial discretization and model parameterization on the prediction of extreme runoff characteristics

Summary Water resources management in mesoscale river basins requires, among other things, reliable predictions on extreme runoff characteristics such as magnitude and frequency of floods and droughts. Hydrologic models are increasingly used for these prediction purposes. Outputs of these models, however, are sensitive to various factors like the spatial representation of hydrologic processes, the parameterization method, and the type of estimator used for calibration. This study aimed to investigate the possible effects of these factors on extreme runoff characteristics derived from simulated streamflow. For this purpose, lumped and distributed versions of the conceptual mesoscale hydrologic model (mHM) were implemented in 22 German basins ranging in size from 58 to 4000 km2. The distributed mHM version was, in turn, parameterized with hydrological response units (HRU) and multiscale parameter regionalization (MPR) methods. Free parameters of both model versions were calibrated with three objective functions emphasizing high flows, low flows, and a combination of both. Six extreme runoff characteristics were derived from daily streamflow simulations for winter and summer. Results indicated that the model performance evaluated with both daily streamflow and seasonal runoff characteristics was sensitive to the type of estimator, the spatial discretization, and the parameterization method employed. The lumped version exhibited the highest sensitivity to previous factors and the least performance, whereas the opposite behavior was noticed for the distributed version parameterized with the MPR technique. Furthermore, the efficiency of the model parameterized with MPR were higher than that obtained with the HRU parameterization, in particular, when the model was evaluated in locations not used for calibration.

Basic Considerations on Upscaling for the Evaporation Model

A grid square of a meso-scale or macro-scale hydrological model usually includes various kinds of single land-use surfaces (elements). In order to estimate three fluxes from a grid square, fluxes from each element have to be averaged. For this purpose, Scale Issue has been researched by many researchers.In this paper, numerical simulations were undertaken and considerations about upscaling from micro-scale to meso-scale was also undertaken, focusing on the aerodynamic resistance between the surface and the ‘blending height’. Defining the resistance of a whole grid square by parallel summation of the corresponding elemental resistances, the areal average fluxes were found to be similar.