Monitoring Water-Related Ecosystems with Earth Observation Data in Support of Sustainable Development Goal (SDG) 6 Reporting

Raha Hakimdavar,Amy Pickens,Brandon Smith,David Lagomasino,Sushel Unninayar,Matthew Hansen,Margaret Hurwitz,Argyro Kavvada,Nima Pahlevan,Stephanie Schollaert Uz,Frederick Policelli,Mark Carroll,Temilola Fatoyinbo,Alfred Hubbard,Danielle Wood

doi:10.3390/rs12101634

Abstract

Lack of national data on water-related ecosystems is a major challenge to achieving the Sustainable Development Goal (SDG) 6 targets by 2030. Monitoring surface water extent, wetlands, and water quality from space can be an important asset for many countries in support of SDG 6 reporting. We demonstrate the potential for Earth observation (EO) data to support country reporting for SDG Indicator 6.6.1, ‘Change in the extent of water-related ecosystems over time’ and identify important considerations for countries using these data for SDG reporting. The spatial extent of water-related ecosystems, and the partial quality of water within these ecosystems is investigated for seven countries. Data from the Moderate Resolution Imaging Spectroradiometer (MODIS) and Landsat 5, 7, and 8 with Shuttle Radar Topography Mission (SRTM) are used to measure surface water extent at 250 m and 30 m spatial resolution, respectively, in Cambodia, Jamaica, Peru, the Philippines, Senegal, Uganda, and Zambia. The extent of mangroves is mapped at 30 m spatial resolution using Landsat 8 Operational Land Imager (OLI), Sentinel-1, and SRTM data for Jamaica, Peru, and Senegal. Using Landsat 8 and Sentinel 2A imagery, total suspended solids and chlorophyll-a are mapped over time for a select number of large surface water bodies in Peru, Senegal, and Zambia. All of the EO datasets used are of global coverage and publicly available at no cost. The temporal consistency and long time-series of many of the datasets enable replicability over time, making reporting of change from baseline values consistent and systematic. We find that statistical comparisons between different surface water data products can help provide some degree of confidence for countries during their validation process and highlight the need for accuracy assessments when using EO-based land change data for SDG reporting. We also raise concern that EO data in the context of SDG Indicator 6.6.1 reporting may be more challenging for some countries, such as small island nations, than others to use in assessing the extent of water-related ecosystems due to scale limitations and climate variability. Country-driven validation of the EO data products remains a priority to ensure successful data integration in support of SDG Indicator 6.6.1 reporting. Multi-country studies such as this one can be valuable tools for helping to guide the evolution of SDG monitoring methodologies and provide a useful resource for countries reporting on water-related ecosystems. The EO data analyses and statistical methods used in this study can be easily replicated for country-driven validation of EO data products in the future.

Highlights

According to the first Sustainable Development Goal (SDG) 6 Synthesis Report released in 2018, the world is not on track to achieve the SDG 6 targets by 2030
Due to the higher spatial resolution of Landsat vs. Moderate Resolution Imaging Spectroradiometer (MODIS), Landsat-based data are able to capture smaller water bodies that may otherwise be missed by MODIS, during years when cloud cover is not a significant issue, Landsat-based estimates of surface water will likely be higher than MODIS-based estimates, as illustrated here
We argue that identifying the type of mangrove gain is an especially critical piece of information for country reporting on SDG Indicator 6.6.1, and one that can be obtained via Earth observation (EO)

Summary

Introduction

According to the first Sustainable Development Goal (SDG) 6 Synthesis Report released in 2018, the world is not on track to achieve the SDG 6 targets by 2030. Lack of available and reliable national data for SDG 6 reporting is listed among the main reasons for this. 60% of the 193 member states do not have adequate data available to meet the reporting requirements of a majority of the SDG 6 indicators [1]. SDG Indicator 6.6.1, ‘Change in the extent of water-related ecosystems over time’, is one of the most data limited. 20% of countries have submitted data on the spatial extent, quantity, and quality of their water-related ecosystems [1]. Assessments have highlighted the potential for countries, where comprehensive ground-based information is lacking or limited, to use satellite-based Earth observation (EO) data in support of Indicator 6.6.1 reporting [1,2,3]

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