Replication of ecologically relevant hydrological indicators following a modified covariance approach to hydrological model parameterization

Abstract

Abstract. Hydrological models can be used to assess the impact of hydrologic alteration on the river ecosystem. However, there are considerable limitations and uncertainties associated with the replication of ecologically relevant hydrological indicators. Vogel and Sankarasubramanian's 2003 (Water Resources Research) covariance approach to model evaluation and parameterization represents a shift away from algorithmic model calibration with traditional performance measures (objective functions). Using the covariance structures of the observed input and simulated output time series, it is possible to assess whether the selected hydrological model is able to capture the relevant underlying processes. From this plausible parameter space, the region of parameter space which best captures (replicates) the characteristics of a hydrological indicator may be identified. In this study, a modified covariance approach is applied to five hydrologically diverse case study catchments with a view to replicating a suite of ecologically relevant hydrological indicators identified through catchment-specific hydroecological models. The identification of the plausible parameter space (here n≈20) is based on the statistical importance of these indicators. Evaluation is with respect to performance and consistency across each catchment, parameter set, and the 40 ecologically relevant hydrological indicators considered. Timing and rate of change indicators are the best and worst replicated respectively. Relative to previous studies, an overall improvement in consistency is observed. This study represents an important advancement towards the robust application of hydrological models for ecological flow studies.

Calibration of hydrological models for ecologically relevant streamflow predictions: a trade-off between fitting well to data and estimating consistent parameter sets?

“…River flow is the cornerstone of freshwater ecosystems, the ecological integrity of which relies on natural fluctuations in the river flow regime (Poff et al, 1997). A long history of human alterations of the river flow regime for water supply, irrigation, flood protection, or hydropower threatens water security and freshwater biodiversity in many regions of the world (Vörösmarty et al, 2010). Richter et al (1997) raised the overarching research question: "How much water does a river need?".…”

eFLaG: enhanced future FLows and Groundwater. A national dataset of hydrological projections based on UKCP18

“…EdGE delivered an ensemble comprising of two GCMs and four 'impact' models (gridded land surface and hydrological models at a 5x5km scale) for the whole of Europe. Visser-Quinn et al (2019) analysed future river flow drought risk in this ensemble, using a similar approach to Collet et al (2018), and found similar results in terms of the spatial distribution and magnitude of future changes in droughts, albeit with some differences arising from the use of different scenarios, GCMs and hydrological models.…”

EURO-CORDEX: A Multi-Model Ensemble Fit for Assessing Future Hydrological Change?

“…It is well-established that hydrological models alone are incapable of modeling all, or even multiple, facets of the flow regime concurrently (Blöschl and Montanari, 2010;e.g., magnitude and timing). These difficulties are highlighted in recent efforts by the hydrological modeling community to replicate specific ecologically relevant "hydrological indicators" (Pool et al, 2017;Visser-Quinn et al, 2019b).…”