Downscaling climate change of water availability, sediment yield and extreme events: Application to a Mediterranean climate basin

Abstract

A robust hydrological impact assessment is indispensable for mitigation and adaptation planning. This study presents an integrated modelling methodology for evaluating climate change impacts on water availability, sediment yield and extreme events at the catchment scale. We propose the use of the spatial–temporal Neyman–Scott Rectangular Pulses (STNSRP) model—RainSim V3 and the rainfall conditioned daily weather generator—ICAAM‐WG, as well as the physically based spatially distributed hydrological model—SHETRAN. The change factor approach was applied for obtaining unbiased rainfall and temperature statistics. The ICAAM‐WG was developed based on the modified Climate Research Unit daily Weather Generator (CRU‐WG). The methodology is proposed to generate synthetic series of hourly precipitation, daily temperature and potential evapotranspiration, hourly runoff and hourly sediment discharge. We demonstrated a possible application in a 705‐km2 Mediterranean climate basin in southern Portugal. The case study showed the evaluation of future climate change impacts on annual and monthly water balance components and sediment yield, annual and seasonal flow duration curves, empirical extreme value distributions and the theoretical fits. It did not consider the possible uncertainty due to the limit of computational resources. The methodology can be well justified as follows: (a) the use of synthetic hourly instead of daily precipitation enables SHETRAN to be more capable of reproducing reliable storm runoff processes and the consequent sediment transport processes; (b) the use of SHETRAN makes possible the impact assessment to be accessible for any model grid square within the study basin; (c) the use of a statistical–stochastic downscaling method facilitates the generation of the synthetic series with unlimited length. It makes possible robust hydrological impact assessments if uncertainties related to the global climate model, regional climate model, greenhouse gas emission scenario, downscaling method, hydrological model and observational data are considered.

Downscaling climate change of mean climatology and extremes of precipitation and temperature: Application to a Mediterranean climate basin

“…Concerning the drought risk for southern Europe, particularly the Mediterranean climate region, the projections of changes in the severity and persistence of dry spells could enable effective and efficient adaptations in water supply management, while simulation of the future occurrence, severity and persistence of hot spells could facilitate effective measures to reduce potential loss of life and economic damage (Guerreiro et al, ). The generated synthetic series of HP and daily PET can also be provided as input to physically based, spatially distributed hydrological models for robust hydrological impact assessments (Zhang et al, ).…”

“…The multi‐site property of RainSimV3 was used in this study, with the model configured to generate synthetic HP series at each rain gauge (Figure ) for future application in storm‐runoff and sediment transport simulations (Zhang et al, ). In order to reproduce mean precipitation climatology and extreme wet and dry events, we selected the following monthly precipitation statistics for RainSimV3 calibration: daily (D) mean ( M DP ) (daily precipitation [DP]) for simulating intra‐annual variation and the total annual precipitation; spatial cross‐correlation among rain gauges (XC DP ) for fitting precipitation correlations among stations; daily variance (Var DP ), skewness (Skew DP ), hourly (H) variance (Var HP ) and skewness (Skew HP ) are for modelling wet precipitation extremes; proportion of dry days (DP < 1.0 mm, Pdry DP1.0 ) and dry hours (HP < 0.1 mm, Pdry HP0.1 ) for fitting probabilities of dry days and hours; and lag − 1 autocorrelation (L1AC DP ) for fitting of persistent events such as long dry spells.…”

“…We configure it with six states (DDD, WDD, WWW, DWW, DW and WD—SIM6) and four states (DD, WW, DW and WD—SIM4) and compare the relative performance of both for the simulation of temperature extremes, including heat waves. Additional tests are made to identify whether RainSimV3 (Burton et al, , see Section 2), which is proposed as the precipitation model component of ICAAM‐WG, and also the temperature component of ICAAM‐WG, can skillfully produce synthetic climate scenarios for robust hydrological impact assessment at middle‐sized basins (Zhang et al, ). To do this, we assess whether the two models reproduce both the mean climatology and realistic extremes at a 705‐km 2 Mediterranean climate basin, in southern Portugal.…”

“…Methodologies presented in Kilsby et al () and Jones et al () are used for construction of control and future climate scenarios with the CF approach used for deriving projections of future precipitation and temperature statistics from RCM outputs. Further, hourly precipitation (HP) series are generated so that statistics of storm‐runoff can be produced more reliably in hydrological modelling (Zhang et al, ).…”

Climate Change Impacts on Soil Erosion and Sediment Yield in a Watershed

“…Several studies have focused on the impacts of climate change on precipitation volume, runoff volume, erosion volume and sediment yield. General Circulation Models (GCMs) have been applied to analyze the impacts of climate change on precipitation characteristic [7][8][9] and river runoff [10,11]. The Soil and Water Assessment Tool (SWAT) model seems to be the most favored by researchers when evaluating the impacts of climate change on flow rate, soil erosion and sediment yield in a The Gaoping River basin is among the worst basins in Taiwan in terms of sediment yield and is highly vulnerable to sediment deposition.…”