Senent‐Aparicio et al. (2022) Recent precipitation trends in Peninsular Spain and implications for water infrastructure design

Identification

• Journal: Journal of Hydrology Regional Studies
• Year: 2022
• Date: 2022-12-19
• Authors: Javier Senent‐Aparicio, Adrián López-Ballesteros, Patricia Jimeno‐Sáez, Julio Pérez‐Sánchez
• DOI: 10.1016/j.ejrh.2022.101308

Research Groups

• Department of Civil Engineering, Universidad Católica de Murcia (UCAM), Murcia, Spain
• Department of Civil Engineering, Universidad de Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Spain

Short Summary

This study updates precipitation trends in Peninsular Spain from 1951 to 2019 and assesses the impact of recent extreme rainfall on water infrastructure design flows, revealing a general decrease in annual precipitation but significant increases (30-40%, up to double) in design flows when recent high-intensity events are incorporated.

Objective

• To update the trends in the magnitude and seasonality of precipitation in Peninsular Spain from 1951 to 2019 at different time scales (annual, seasonal, monthly, number of rainy days, maximum daily precipitation).
• To analyze how extreme precipitation events recorded in recent years modify water infrastructure design flows, specifically assessing the effect of incorporating high-intensity rainfall events on flows used for infrastructure design according to Spanish methodologies.

Study Configuration

• Spatial Scale: Peninsular Spain (continental part, 493,515 square kilometers). Gridded dataset with a resolution of 5 kilometers. Design flow analysis focused on 12 selected small basins, each with an area less than 50 square kilometers.
• Temporal Scale: Precipitation data analyzed for the period 1951–2019. Design flow calculations compared a baseline period (1951–1990) with the recent period (1951–2019).

Methodology and Data

• Models used:
  • Modified Mann–Kendall test (from "modifiedmk" R package) for trend detection.
  • Sen’s slope estimator for trend magnitude.
  • SQRT-ET max distribution for statistical analysis of annual maximum daily rainfall (PCPmax).
  • Modified Rational Method (MR) from Norm 5.2-IC of the Spanish Highway Instruction for estimating maximum annual flow (Qmax) in small basins.
  • EasyBasin: An open-source QGIS plugin developed in Python 3 for optimizing MR application and design flow calculations.
• Data sources:
  • Daily rainfall data (1951–2019) from the second version of the national gridded dataset developed by the Spanish Meteorological Agency (AEMET), derived from 3236 rainfall stations with a 5-kilometer resolution.
  • Köppen climate classification map for basin selection.
  • Specific maps and parameters for Spain (initial runoff threshold map, torrentiality index map, regional classification map of the runoff correction factor) integrated into the EasyBasin plugin, based on Norm 5.2-IC and Ferrer Juliá et al. (2004).

Main Results

• Annual precipitation shows a decreasing trend in 18% of the territory, with less than 1% showing an increasing trend (primarily in the north).
• Seasonally, precipitation decreases are concentrated in summer and, to a lesser extent, autumn. Monthly, significant reductions were observed in March (27% negative trend) and June (65% negative trend), while April and September showed generally positive trends (7%).
• The number of rainy days exhibited a general decreasing trend across most of the country, with 76.39% of grid points showing a significant negative annual trend. June was particularly affected, with over 80% of points indicating a significant negative trend.
• Maximum daily rainfall (PCPmax) showed a predominantly positive annual trend in 29.47% of the territory, with only 1.39% showing a decrease. This positive trend was observed seasonally, except in summer.
• Overall, the study indicates a decrease in the number of rainy days but an increase in the intensity of rainfall events.
• Incorporating recent high-intensity rainfall data (1951-2019 period) into design flow calculations resulted in significant increases in maximum annual flow (Qmax) compared to using older data (1951-1990 period).
  • Qmax increased by 3.6% to 69.5% for a 10-year return period.
  • Qmax increased by 9.9% to 115.1% for a 100-year return period.
  • Qmax increased by 9.1% to 128.6% for a 500-year return period.
• Average increases in design flows were approximately 30-40%, reaching double the baseline values in some basins, highlighting a severe underestimation risk if outdated rainfall data is used.

Contributions

• Provided an updated and comprehensive analysis of precipitation trends (magnitude and seasonality) across Peninsular Spain from 1951 to 2019 at multiple temporal scales.
• Quantified for the first time the direct impact of incorporating recent high-intensity storm events on water infrastructure design flows in Spain, demonstrating significant underestimation risks with older data.
• Developed and released the open-source EasyBasin QGIS plugin, a practical tool for calculating design flows in small basins according to Spanish regulations, making the methodology more accessible and efficient.
• Offered a robust technical basis for competent authorities to formally consider updating current water infrastructure design standards and flood maps to account for recent climate change impacts.

Funding

• European Union’s Horizon 2020 Research and Innovation Programme (Grant Agreement No. 101017861)
• Spanish Ministry of Science and Innovation (Grant PID2021-128126OA-I00)
• Ministry of Education, Culture and Sport of Spain (FPU grant FPU17/00923 for Adrián López-Ballesteros)

Citation

@article{SenentAparicio2022Recent,
  author = {Senent‐Aparicio, Javier and López-Ballesteros, Adrián and Jimeno‐Sáez, Patricia and Pérez‐Sánchez, Julio},
  title = {Recent precipitation trends in Peninsular Spain and implications for water infrastructure design},
  journal = {Journal of Hydrology Regional Studies},
  year = {2022},
  doi = {10.1016/j.ejrh.2022.101308},
  url = {https://doi.org/10.1016/j.ejrh.2022.101308}
}