A Remote Sensing-Based Method to Assess Water Level Fluctuations in Wetlands in Southern Brazil

João P D Simioni,Thiago V Dos Santos,Guilherme A V Mataveli,Gabriel De Oliveira,Laurindo A Guasselli

doi:10.3390/geohazards1010003

Abstract

The characterization of water level fluctuations is crucial to explain the hydrological processes that contribute to the maintenance of the structure and function of wetlands. The aim of this study was to develop a method based on remote sensing to characterize and map the water level variation patterns, evapotranspiration, discharge, and rainfall over wetlands in the Gravataí River basin, Rio Grande do Sul (RS), Brazil. For this purpose, ground-based measurements of rainfall, water discharge, and evapotranspiration together with satellite data were used to identify the apparent water level based on the normalized difference water index (NDWI). Our results showed that the variation of the water level followed the rainfall, water discharge, and evapotranspiration seasonal patterns in the region. The NDWI showed similar values to the ground-based data collected 10 days prior to satellite image acquisition. The proposed technique allows for quantifying the pattern of flood pulses, which play an important role for establishing the connectivity between different compartments of wetlands in the study area. We conclude that our methodology based on the use of satellite data and ground measurements was a useful proposition to analyze the water level variation patterns in an area of great importance in terms of environmental degradation and use of agriculture. The information obtained may be used as inputs in hydrologic models, allowing researchers to evaluate the impact, at both local and regional scales, caused by advance of agriculture into natural environments such as wetlands.

Highlights

Water level fluctuations affect ecological processes and lake patterns [1,2,3,4]
We in note that theofwater for rice cultivation in the Environmental Protection Area of Banhado Grande (EPABG) may influence the dynamics of water level fluctuations
The importance of considering rice cultivation in the characterization of water level fluctuations was discussed by Tassi [40], who modeled the hydroperiod for the Taim marsh, southern Brazil, based on meteorological and water use data for agricultural cultivation

Summary

Introduction

Water level fluctuations affect ecological processes and lake patterns [1,2,3,4]. The characterization of water level fluctuations is the basis for understanding the temporal limnological changes in these environments [5,6]. Oscillatory fluctuations are not the only type of changes in water levels that can occur in wetlands. Water level fluctuations may generate more productive and diversified habitats, they may have negative effects on lake ecosystems and their services, such as eutrophication, cyanobacteria proliferation, and even increased susceptibility to invasive species [1,4,10,12]. Deposition of nutrients from sediments contributes to high yield rates in wetland areas, and for this reason they are considered one of the most productive natural environments [13]

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Discussion

Conclusion