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Using Landsat 8 Images for Monitoring Surface Water Temperature in an Urban Tropical Reservoir

Wermuth L, de Sousa LFMF, de Carvalho LAS, de Oliveira N, Silva T (2022)

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Publication Type: Conference contribution

Publication year: 2022

Publisher: International Association for Hydro-Environment Engineering and Research

Pages Range: 5351-5358

Conference Proceedings Title: Proceedings of the IAHR World Congress

Event location: Granada, ESP

DOI: 10.3850/IAHR-39WC2521716X20221047

Abstract

Reservoirs play an important role, especially in urban tropical regions, where they often serve as water supply, energy production, flood prevention and recreational areas. The Pampulha reservoir (surface area 1.97 km2, maximum depth 16.17 m), located in Belo Horizonte, Brazil, is an artificial reservoir. Since the 1970's, the frequency of algal blooms, particularly cyanobacteria, has increased, mainly due to eutrophication caused by the contamination by the input of nutrients from the ongoing urbanization of its tributaries catchments. Water temperature is an important driver for water dynamics, physical and biochemical processes in inland water bodies and its monitoring is desirable for a better understanding of water quality management processes. Remote sensing techniques can be used to monitor surface water temperature (SWT) and provide the opportunity of complementing in situ data. This study aims to assess two methods to retrieve SWT from Landsat 8 (LS8) images of Pampulha reservoir, the Statistical Mono-Window (SMW) algorithm and the Split-Window (SW) algorithm using Google Earth Engine (GEE). A provided code repository of the SMW algorithm within GEE was used directly, whereas the SW algorithm was implemented in GEE by the authors. Both algorithms retrieved water temperature values for dates whenever an applied cloud mask admitted it and CSV-files holding these data were downloaded directly from GEE. Hourly in situ data of Pampulha reservoir were available from January 2015 until November 2017 and were compared to LS8 retrieved SWT values. Results from both SMW (RMSE =2.21 0C, R2 = 0.29) and SW (RMSE = 1.48 0C, R2 = 0.63) algorithms were similar to results found in other studies, however, the later method showed more satisfactory results in Pampulha reservoir. Using the SW algorithm, a time series of SWT in Pampulha reservoir of available LS8 information from 2013 up to 2020 and thermal maps showing the mean monthly SWT were generated to characterize temporal and spatial thermal behavior of the reservoir. The time series showed a seasonal pattern with higher water temperature values during the wet and warm season (November to March) and lower water temperature values during the dry and cold season (June to August). Lower water temperatures can generally be found in more central areas of the reservoir. Derived SWT values of Landsat 8 using the Split-Window algorithm were representative of in situ SWT values and can be used for monitoring urban tropical reservoirs, in particular, eminently polluted ones. Especially in countries with a lack of investment for in situ monitoring such as Brazil, Landsat 8 derived SWT depicts a great source of complementary information regarding water body and resource management.

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How to cite

APA:

Wermuth, L., de Sousa, L.F.M.F., de Carvalho, L.A.S., de Oliveira, N., & Silva, T. (2022). Using Landsat 8 Images for Monitoring Surface Water Temperature in an Urban Tropical Reservoir. In Proceedings of the IAHR World Congress (pp. 5351-5358). Granada, ESP: International Association for Hydro-Environment Engineering and Research.

MLA:

Wermuth, Laura, et al. "Using Landsat 8 Images for Monitoring Surface Water Temperature in an Urban Tropical Reservoir." Proceedings of the 39th IAHR World Congress, 2022, Granada, ESP International Association for Hydro-Environment Engineering and Research, 2022. 5351-5358.

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