Climate change impacts model parameter sensitivity – implications for calibration strategy and model diagnostic evaluation
2021
Abstract. Hydrological models are useful tools for exploring the impact of climate change. To prioritize parameters for calibration and to evaluate hydrological
model functioning, sensitivity analysis can be conducted. Parameter
sensitivity, however, varies over climate, and therefore climate change could
influence parameter sensitivity. In this study we explore the change in
parameter sensitivity for the mean discharge and the timing of the discharge,
within a plausible climate change rate. We investigate whether changes in sensitivity propagate into the calibration strategy and diagnostically compare three hydrological models based on the sensitivity results. We
employed three frequently used hydrological models (SAC, VIC, and HBV) and explored parameter sensitivity changes across 605 catchments in the United
States by comparing GCM(RCP8.5)-forced historical and future
periods. Consistent among all hydrological models and both for the mean
discharge and the timing of the discharge is that the sensitivity of snow parameters decreases in the future. Which other parameters increase in
sensitivity is less consistent among the hydrological models. In 45 %
to 55 % of the catchments, dependent on the hydrological model, at
least one parameter changes in the future in the top-5 most sensitive
parameters for mean discharge. For the timing, this varies between
40 % and 88 % . This requires an adapted calibration strategy
for long-term projections, for which we provide several suggestions. The
disagreement among the models on the processes that become more relevant in
future projections also calls for a strict evaluation of the adequacy of the
model structure for long-term simulations.
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