Rodrigues et al. (2025) Estimating Reservoir Evaporation Under Mediterranean Climate Using Indirect Methods: A Case Study in Southern Portugal

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Identification

• Journal: Hydrology
• Year: 2025
• Date: 2025-10-31
• Authors: Carlos Miranda Rodrigues, Rita Cabral Guimarães, Madalena Moreira
• DOI: 10.3390/hydrology12110286

Research Groups

Not explicitly provided in the paper text.

Short Summary

This study assessed reservoir evaporation patterns in southern Portugal using offshore meteorological data and benchmarked five indirect evaporation methods against the Energy Budget method, finding good correlation and small biases for all methods, especially in the dry semester.

Objective

• Assess the reservoir evaporation pattern in southern Portugal from meteorological offshore measures.
• Benchmark various indirect methods for evaluating reservoir evaporation at a monthly scale.
• Provide recommendations on the most suitable indirect method to apply in operational practices.

Study Configuration

• Spatial Scale: Nine reservoirs in the Alentejo and Algarve regions of southern Portugal.
• Temporal Scale: Monthly scale, with results presented as monthly rates and annual averages.

Methodology and Data

• Models used:
  • Energy Budget (Bowen Ratio) method (reference method)
  • Mass Transfer (MT)
  • Penman (PEN)
  • Priestley and Taylor (PT)
  • Thornthwaite (THOR)
  • Pan Evaporation (PE)
• Data sources: Meteorological data collected from floating weather stations on instrumented platforms across nine reservoirs (offshore local measurements).

Main Results

• Monthly evaporation rates across the nine reservoirs ranged from 0.8 mm d⁻¹ in winter to 4.6 mm d⁻¹ in summer.
• The annual average evaporation rate was 2.7 mm d⁻¹.
• Annual evaporation values ranged from 750 mm to 1230 mm, showing a positive gradient from northern Alentejo to southwest Algarve.
• All five studied indirect methods (MT, PEN, PT, THOR, PE) produced estimates with good correlation to the Energy Budget method's results across all reservoirs.
• All methods showed small biases at the monthly scale, particularly in the dry semester.
• The evaporation variability of estimates depended on the specific reservoir.
• A new N function of reservoir superficial area is presented for the Mass Transfer method in Mediterranean climate regions.

Contributions

• First study to make available a significant number of offshore local measurements for reservoir evaporation in a Mediterranean climate region.
• Provides a comprehensive benchmarking of five empirical and semi-empirical evaporation methods against the Energy Budget method using unique offshore data.
• Offers practical recommendations for water managers on selecting suitable evaporation estimation methods based on data availability and reservoir characteristics in Mediterranean climates.
• Introduces a new N function for the Mass Transfer method specifically tailored for Mediterranean climate regions.

Funding

Not explicitly provided in the paper text.

Citation

@article{Rodrigues2025Estimating,
  author = {Rodrigues, Carlos Miranda and Guimarães, Rita Cabral and Moreira, Madalena},
  title = {Estimating Reservoir Evaporation Under Mediterranean Climate Using Indirect Methods: A Case Study in Southern Portugal},
  journal = {Hydrology},
  year = {2025},
  doi = {10.3390/hydrology12110286},
  url = {https://doi.org/10.3390/hydrology12110286}
}