Improving runoff estimates from regional climate models: a performance analysis in Spain

Abstract

An important aspect to assess the impact of climate change on water availability is to have monthly time series representative of the current situation. In this context, a simple methodology is presented for application in large-scale studies in regions where a properly calibrated hydrologic model is not available, using the output variables simulated by regional climate models (RCMs) of the European project PRUDENCE under current climate conditions (period 1961–1990). The methodology compares different interpolation methods and alternatives to generate annual times series that minimize the bias with respect to observed values. The objective is to identify the best alternative to obtain bias-corrected, monthly runoff time series from the output of RCM simulations. This study uses information from 338 basins in Spain that cover the entire mainland territory and whose observed values of naturalised runoff have been estimated by the distributed hydrological model SIMPA. Four interpolation methods for downscaling runoff to the basin scale from 10 RCMs are compared with emphasis on the ability of each method to reproduce the observed behavior of this variable. The alternatives consider the use of the direct runoff of the RCMs and the mean annual runoff calculated using five functional forms of the aridity index, defined as the ratio between potential evaporation and precipitation. In addition, the comparison with respect to the global runoff reference of the UNH/GRDC dataset is evaluated, as a contrast of the "best estimator" of current runoff on a large scale. Results show that the bias is minimised using the direct original interpolation method and the best alternative for bias correction of the monthly direct runoff time series of RCMs is the UNH/GRDC dataset, although the formula proposed by Schreiber also gives good results

Grey water footprint assessment at the river basin level: Accounting method and case study in the Segura River Basin, Spain

“…SIMPA (Gonzalez-Zeas et al, 2012) is a distributed model at a monthly time-scale, used by the water board of the Segura River Basin to establish the natural water resources available (CHS, 2013a). The DSS Optiges is the optimisation module of AquatoolDMA (Paredes-Arquiola et al, 2014), one of the most-frequently-used platforms of water resources management (Salla et al, 2014).…”

Runoff Trends Driven by Climate and Afforestation in a Pyrenean Basin

“…Álvarez et al, 2004). This model estimates ETP by means of a combination of the Thornthwaite and Penman-Monteith methods and also uses a factor that accounts for the vegetation effect (Estrela & Quintas, 1996;González-Zeas et al, 2012). Climate data were raster-type data (i.e.…”

Hydrologic Determinants of Climate Change Impacts on Regulated Water Resources Systems

“…There is a great variability in the results provided by the 10 RCMs. According to a previous study (González-Zeas et al 2012), the most suitable model under current situation for the area of Spain is GKSS, followed by UCM and SMHI. However, considering the existing bias of the climate models, the observed streamflow estimated by SIMPA model has been used to generate the climate change projections.…”