Choosing an arbitrary calibration period for hydrologic models: How much does it influence water balance simulations?. Issue 2 (18th February 2021)

• Record Type: Journal Article
• Authors: Myers, Daniel T.; Ficklin, Darren L.; Robeson, Scott M.; Neupane, Ram P.; Botero‐Acosta, Alejandra; Avellaneda, Pedro M.
• Is Part Of: Hydrological processes. Volume 35:Issue 2(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-02-18
• Subjects: calibration -- evapotranspiration -- hydrology -- model -- nonstationarity -- parameter -- runoff -- snowmelt; Hydrology -- Periodicals; Hydrology -- Research -- Periodicals; Hydrologic models -- Periodicals; Hydrological forecasting -- Periodicals; 631.432
• DOI: 10.1002/hyp.14045
• Languages: English
• ISSNs: 0885-6087

Abstract

Abstract: The selection of calibration and validation time periods in hydrologic modelling is often done arbitrarily. Nonstationarity can lead to an optimal parameter set for one period which may not accurately simulate another. However, there is still much to be learned about the responses of hydrologic models to nonstationary conditions. We investigated how the selection of calibration and validation periods can influence water balance simulations. We calibrated Soil and Water Assessment Tool hydrologic models with observed streamflow for three United States watersheds (St. Joseph River of Indiana/Michigan, Escambia River of Florida/Alabama, and Cottonwood Creek of California), using time period splits for calibration/validation. We found that the choice of calibration period (with different patterns of observed streamflow, precipitation, and air temperature) influenced the parameter sets, leading to dissimilar simulations of water balance components. In the Cottonwood Creek watershed, simulations of 50‐year mean January streamflow varied by 32%, because of lower winter precipitation and air temperature in earlier calibration periods on calibrated parameters, which impaired the ability for models calibrated to earlier periods to simulate later periods. Peaks of actual evapotranspiration for this watershed also shifted from April to May due to different parameter values depending on the calibration period's winter air temperatures. In the St. Joseph and Escambia River watersheds, adjustments of the runoff curve number parameter could vary by 10.7% and 20.8%, respectively, while 50‐year mean monthly surface runoff simulations could vary by 23%–37% and 169%–209%, depending on the observed streamflow and precipitation of the chosen calibration period. It is imperative that calibration and validation time periods are chosen selectively instead of arbitrarily, for instance using change point detection methods, and that the calibration periods are appropriate for the goals of the study, considering possible broad effects of nonstationary time series on water balance simulations. It is also crucial that the hydrologic modelling community improves existing calibration and validation practices to better include nonstationary processes. Abstract : We investigated how much the choice of calibration period can affect water balances in Soil and Water Assessment Tool models of three United States watersheds. We found that this choice can cause substantial changes in snowmelt, evapotranspiration, surface runoff, soil water, and groundwater flow simulations. Thus, any study that is relying on these unmeasured components (e.g., water quality, climate change impacts, and best management practice studies) should choose calibration periods selectively and carefully.