Abstract
AbstractGlobal hydrological models (GHMs) have become an established tool to simulate water resources worldwide. Most of the GHMs are however uncalibrated and typically use a set of basic hydrological parameters, that could potentially lead to unrealistic projections of the terrestrial water cycle. The calibration of hydrological models is usually performed by using and comparing modeled to observed discharge. Accurate station data and reliable time series data of discharge are, however, often not available for many parts of the world and classic calibration approaches are therefore not feasible. In this paper, we aim to develop a new calibration approach that requires no additional data, is easy to implement, and substantially improves model performance, especially in regions where uncalibrated model performance is rather poor. This is achieved by using the Budyko framework, which provides a conceptual representation of the long‐term water and energy balance. We use a state‐of‐the‐art GHM and calibrate the model within nine river catchments of different sizes and characteristics. Since observed river discharge is available for these catchments, we are able to compare the Budyko‐based calibration approach to a classic discharge‐based calibration scheme and the uncalibrated model version. In all catchments, the Budyko‐based calibration approach decreases biases and increases model performance compared to the uncalibrated model version although performance improvements obtained through a classic calibration approach are greater. Nonetheless, a Budyko‐based calibration is a valuable, intermediate approach between use of a basic set of a priori hydrological parameters and classical calibration against discharge data.
Highlights
The Budyko-based calibration approach decreases biases and increases model performance compared to the uncalibrated model version performance improvements obtained through a classic calibration approach are greater
Using the Budyko framework enables us to ensure a good representation of the basic characteristics of the long-term coupled water and energy balance, and we argue that, given its simplicity and data requirements, an implementation into existing calibration tools is easy and efficient
Instead of determining a parameter set best representing observed discharge, the overarching goal of this study is to show the potential of calibrating a parameter set that best represents the Budyko curve, including variability in ω, thereby ensuring a model setup that provides a reasonable estimate of the long-term water balance as a function of climatic aridity
Summary
Global hydrological models (GHMs) have become a common tool to assess the large-scale dynamics of surface and subsurface hydrological processes, ranging from more classical hydrologic modeling approaches focusing on small catchment areas, up to continental-basin scales. Using the Budyko framework enables us to ensure a good representation of the basic characteristics of the long-term coupled water and energy balance, and we argue that, given its simplicity and data requirements, an implementation into existing calibration tools is easy and efficient We hypothesize that this approach will reduce runoff biases but not the subdaily to seasonal modeling of high and low flows and that it will provide a major and simple step toward more reliable large-scale hydrological modeling in data-scarce and ungauged regions. Instead of determining a parameter set best representing observed discharge, the overarching goal of this study is to show the potential of calibrating a parameter set that best represents the Budyko curve, including variability in ω, thereby ensuring a model setup that provides a reasonable estimate of the long-term water balance as a function of climatic aridity. After presenting the results (section 4), we discuss the advantages and possible limitations of the Budyko-based calibration approach (section 5) before outlining the potential for future developments and further improvements (section 6)
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