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Tracking the health of Africa’s lakes and reservoirs has long been a challenge; traditional monitoring methods are costly, inconsistent, and often leave huge data gaps. To bridge that divide, Digital Earth Africa has developed the Water Quality SDG Notebook, a practical tool that helps countries assess and report on Sustainable Development Goal Indicator 6.6.1 using satellite-derived data. Built on top of DE Africa’s existing Waterbodies Service and leveraging globally recognised methodologies, the notebook gives governments and environmental managers a ready-made workflow to evaluate turbidity and trophic state across their national waterbodies. In this Q&A, we explore the thinking behind the notebook, standout findings, and how this work is evolving into a full-fledged Water Quality Service for the continent.
What inspired the development of the Water Quality SDG Notebook, and what gap or challenge were you aiming to address?
As a continuation of the work on monitoring waterbodies, DE Africa is building on the Waterbodies Service to create the Water Quality Service (WQS). This service aims to generate information on water quality for users across Africa. Assisting national governments to report on the SDG Indicator 6.6.1 is a key use case where DE Africa can assist by managing the EO data and providing the processing workflow and tools. The logical first step in this use case was to implement the recommended SDG 6.6.1 methodology using the Copernicus Land Service Lake Water quality products now available through the DE Africa platform. The notebook demonstrates how to calculate national-scale statistics for lake Turbidity and Trophic State using the SDG Indicator 6.6.1 default methodology.
How did you select the indicators or EO datasets used in the notebook, and how do they align with the SDG 6 targets?
In this notebook, we want to give countries the ability to take full control of their SDG reporting for Indicator 6.6.1, based on the default methodology (i.e. the currently documented method that can be used globally). The default methodology specifies Trophic State and Turbidity of lakes as indicators so we produce those. It also uses the Copernicus Global Land Service (CGLS) 300m resolution 2002-2012, 2016-2024 and 2024-present Lake Water Quality products. The default methods are used to measure water quality for 4,200 lakes globally. Approximately 311 of these are in Africa, however this is a tiny fraction of all the waterbodies in Africa. In the future, we aim to extend these analyses to use DEAfrica’s water quality products to support more flexible monitoring and reporting at a higher resolution and for waterbodies as small as 1 Ha.
Could you share a few standout insights or findings from the notebook that might be surprising or especially relevant to policymakers or environmental managers in Africa?
Between 2021 (the most recent year shown in in the SDG 6.6.1 app) and 2024, Rwanda’s lakes show a marked improvement in trophic state conditions. The proportion of waterbodies classified as affected by high trophic state declined from 25% in 2021 to 0% in 2024. However, the proportion of lakes affected by high turbidity has not changed over the period, holding steady at 12.5%.
You mentioned you’re working on the Water Quality Service. How does this build on the notebook, and what can users expect from the service?
The WQS aims to generate information on water quality for the areas identified as water bodies in the DE Africa water bodies service. This information includes:
- State of the waterbody, such as its trophic state classification or general turbidity levels
- Trend in water quality; whether the WQ appears to be improving, declining, or constant
- Change in water quality; whether the WQ appears to have changed, relative to a baseline period
This information will be consistent with the reporting frameworks of the sustainable development goals (SDGs) and can support national SDG reporting. The user will be able to access water quality data on a regular and more frequent time-base compared to the national reporting for waterbodies of specific interest.
What are the opportunities for integrating this water quality notebook with other SDG indicators across DE Africa e.g land degradation/agric etc?
The outputs generated by the SDG 6.6.1 water quality notebook provide both critical outputs and validation datasets for a wide range of other indicators. This is because the Sustainable Development Goals (SDGs) were intentionally designed to be integrated and indivisible, a concept that extends to their methodologies. For instance, water quality measurements are used to determine if current agricultural practices are causing pollution, which is a key component of SDG Indicator 2.4.1 (sustainable agriculture). The excessive use of fertilizers results in nitrogen and phosphorus runoff from farm fields, washing into waterbodies and causing eutrophication. Furthermore, changes in water quality provide evidence of pressures like soil erosion, which impacts freshwater ecosystems and is directly relevant to land degradation indicators such as SDG 15.3.1 (proportion of degraded land) and 15.1.2 (freshwater biodiversity).
Are there particular countries or water bodies in Africa that offer strong examples of how EO data is being used, or could be used, for water quality monitoring and decision-making?
We are aware of some countries that are seeking to be able to report on SDG 6.6.1 and we hope that they will be able to adopt this notebook. A different example is Water Hyacinth, which is a problem across a number of rift lakes including Lake Victoria and Hartbeespoort dam in South Africa where it poses a significant risk to boaters. One potential use of a water quality service is to support managers to monitor the rapidly changing extent of Water Hyacinth and to plan warnings and interventions.
What has been your experience collaborating across teams on this initiative, and how important is that partnership for scaling impact?
As with other continental services such as the Waterbodies Service that we produce, the Water Quality Service is designed and developed in collaboration with our implementing partners across the continent. This collaboration ensures ownership and proper use by stakeholders and decision-makers.
Lastly, how do you envision EO-based tools like this notebook supporting governments, communities, and researchers in their efforts to combat water pollution and address climate-driven water challenges?
Gathering data on water quality is difficult, and Earth observation is a rich source of information. EO data allows people to measure water quality for entire areas, and also to visualise and communicate changes (think of the spread of turbid plumes flowing into a lake). We are aiming to empower governments, communities and researchers with information that they can use to understand, communicate and take action.
This notebook is a start. It provides decision makers, water managers and water users in both the private sector and civil society with a reusable and reproducible workflow that can be applied to any African nation to give up-to-date information on the state of individual waterbodies and condition of all waterbodies in the country. This removes the need for them to develop the skills and systems to produce the information themselves.
Links:
- SDG Indicator 6.6.1 methodology: https://worldbank.github.io/sdg-metadata/metadata/en/6-6-1a/
- Water Quality Notebooks: