| Timeline | From October 2023 to 30 October 2027 |
|---|---|
| Theme | Resource security |
| Countries | Zimbabwe |
| Funded by | NWO |
Water hyacinths: Use them or lose them? Improving human and ecosystem health by bringing the science to the people of Lake Chivero, Zimbabwe (WHYimprove)
Water hyacinth (WHY) is an invasive species in (sub-)tropical inland waterbodies that clogs waterways and intakes and affects aquatic life and human activities, and may facilitate the spread of diseases. On the other hand, WHY can be exploited for biofuel production and other sources of income. A sustainable solution to water hyacinth infestation “uses” WHY instead of only attempting to “lose” them. This project uses scientific studies of data collected on site, in the lab and from satellites, combined with stakeholder experiences to co-create such solutions for Lake Chivero, the main source of drinking water to Harare, capital of Zimbabwe.
Figure 1: Schematic of the holistic approach of the WHYimprove project (pictograms by flaticon.com)
To be both effective and sustainable, new strategies to manage WHY need to be developed with a holistic view that accounts for humans, society and the ecosystem; users and managers; scientists and stakeholders. Our approach is composed of four elements:
These elements are addressed in six work packages:
The first step in a systematic study of causes and effects of water hyacinth (WHY) is monitoring of the plants’ occurrence on Lake Chivero. The free-floating plants are highly variable in space and time, therefore, occasional ground-based observations, for example from the dam wall, are not sufficient; and mapping out the vegetation on the lake by boat is cumbersome. Fortunately, WHY can be clearly distinguished by remote sensing instruments, like MSI on ESA’s Sentinel-2 mission.
Who: Finn Münch (PhD student), Marloes Penning de Vries (co-promotor), Daphne van der Wal (promotor), Timothy Dube, Cletah Shoko (advisors).
Within the framework of WP1, Finn Münch is developing an algorithm to detect and monitor WHY from space. There are a number of vegetation indices available for vegetation monitoring, but the new Aquatic Macrophyte Index is more adept at separating WHY from algal blooms, which also occur frequently in eutrophic water bodies like Lake Chivero. The work was presented at the EGU conference in Vienna (Münch et al., 2025) and is currently being prepared for publication.
Each new satellite algorithm requires rigorous testing and benchmarking against reference data: validation. However, the variability of WHY makes the collection of ground-based reference data, for example, from a boat, difficult to achieve. Within the time it takes to map out WHY mats for the whole extent of the Lake, the patterns may have changed noticeably. Observations by airborne imaging instruments offer a solution. Therefore, a field campaign to perform UAV measurements over Lake Chivero is planned during the dry season in August/September 2025.
The validated algorithm will finally be used to create timeseries of WHY occurrence. These will be used in WP2 to investigate the drivers of WHY patterns on Lake Chivero. The same timeseries are required for the statistical analysis planned in Work Package 4, which will explore a correlation between WHY and occurrence of diseases.
An important output of WP1 is the global AMI timeseries, which will be published in an open-access form, so that researchers of inland waters affected by WHY or other macrophytes worldwide can use the AMI for their projects. The link to the dataset will be posted here as soon as the data becomes available.
What influences the WHY patterns? Which drivers cause it to thrive or move about, and which inhibit its proliferation? Improving the understanding of the variability of WHY allows the development of a model to describe WHY occurrence patterns. Models can be used to predict future patterns based on information regarding the main drivers. This could be used to inform stakeholders in advance where WHY may build up so that it can be harvested (see WP5) or avoided by fishermen. In combination with the findings from WP4, it can be used as a tool for early warning of disease.
Who: Finn Münch (PhD student), Marloes Penning de Vries (co-promotor), Daphne van der Wal (promotor), Timothy Dube, Cletah Shoko, Lisette de Senerpont Domis (advisors)
This work package forms the second half of Finn Münch's PhD project. After creating a WHY timeseries in WP1, he will examine the relationships between meteorological and other environmental data sets on the one hand, and WHY patterns on the other. This will lead to the identification of the main drivers of WHY variability. Another focus will be the co-variability of WHY and algal blooms.
Figure 2.1. One major driver of WHY variability is wind. The image shows drift monitoring on 2022-07-25 by SuperDove at 9:40 AM, Landsat 9 at 10 AM and Sentinel-2 at 10:15 AM East African Time (EAT). The WHY areas indicated by Sentinel-2 and Landsat 9 were classified using the AMI. Based on the SuperDove’s False Color Composite (FCC) the WHY cover can be estimated. Image by Finn Münch.
The causes and drivers identified from the timeseries will be used as foundation for the development of a WHY occurrence model. Previous research indicates that besides climatological data also hydrological as well as data on the riparian land cover needs to be considered to model the WHY propagation and distribution. Accordingly, the model proposed for this thesis will use a variety of environmental variables and additionally incorporate a surface flow model to account for the drift of WHY.
The WHY occurrence model will be adapted for use as a tool to support policy making and decision taking by stakeholders. It will be integrated into the WHY dashboard (Fig. 2.2) that is being created by Zimbabwe’s Environmental Management Agency, EMA.
Figure 2.2. Sketch of the proposed WHYimprove dashboard. The schematic of the dashboard is based on the EMA air quality dashboard (https://www.ema.co.zw/AirQ/home.html).
The main question this WP seeks to answer is: how are people affected by the occurrence of water hyacinth on Lake Chivero from a Water-Energy-Food nexus perspective? This question is addressed both “bottom-up”, i.e., by surveying stakeholders. And in a “top-down” approach, by examining the satellite data from WP1 .
In the course of the project, it was decided to integrate the topics of WP3 into WP4, for the bottom-up view and WP2, for the top-down view.
Figure 3.1. Water hyacinth near the shores of Lake Chivero (Photo by Marloes Penning de Vries)
Lake Chivero is the main freshwater supply for Harare and nearby towns, a source of income and food for local communities, a recreational area for people from the region and is situated in a nature reserve known for its large game. A deterioration in water quality and accompanying invasion of the lake by water hyacinths is expected to have effects on human health, societal health, and ecological health. These can be investigated in an objective manner, using satellite and other data; but it is similarly important to understand the perspective of different stakeholders.
The main question this WP aims to address is:
How are water quality, water hyacinth and human health connected? Should we encourage stakeholders (from communities to policymakers) to “use” water hyacinth or “lose” them?
This workpackage forms the PhD project of Mgcini Ncube.
Who: Mgcini Ncube (PhD student), Marloes Penning de Vries (co-promotor), Lisette de Senerpont Domis (promotor), Carmen Anthonj, Timothy Dube, Thomas Marambanyika, Ntandokamlimu Nondo, Frank Osei (advisors)
To map out the perspective of stakeholders on the risks related to the use of Lake Chivero (with a focus on fishing), a field campaign is planned for August-September, 2025. Working closely with project partner Environmental Management Agency (EMA), Mgcini Ncube will conduct surveys and interviews among different stakeholders, such as communities (fishermen, vendors and consumers of fish), environment regulators and environmental health practitioners such as parks managers, clinics and local authorities.
The second sub-objective is understanding the role of Lake Chivero in removal of nutrients and pollutants from wastewater. Effluent from the surrounding (urban) regions is discharged into the Lake with little prior treatment. Subsequently, water is abstracted from the Lake to be used as drinking water. By characterizing the temporal variation in microbial load within the lake and across the lake–urban water cycle, we aim to assess the lake’s capacity to regulate pathogen presence and to estimate its role as an ecological determinant in the transmission dynamics of water-related diseases.
Finally, the relationship between WHY, water quality, and the occurrence of cholera, will be investigated. For this, the satellite data produced in WP1 will be used in conjunction with disease records from the hospitals and the Ministry of health by means of statistical epidemiological analysis. If a robust correlation between the state of the Lake (WHY or algae cover fraction) and cholera occurrences can be established, the findings will be used to create a disease prediction model that can be used to issue early warnings of enhanced cholera risk to local authorities and clinics.
Figure 4.1. Personnel of a clinic near Lake Chivero explaining the work and facilities to the WHYimprove team. Photo by Marloes Penning de Vries.
Water hyacinths are not only a pest: they can be used in fertiliser or fodder, as biofuel or created into disposables or handicrafts that may be used directly or sold to generate income. Within WP5, the possibilities of WHY valorisation are investigated for the particular case of Lake Chivero.
Who: Onalenna Gwate (postdoctoral researcher), Timothy Dube (supervisor), Piet Lens (supervisor), Ntandokamlimu Nondo, Marloes Penning de Vries (advisors)
A number of studies concerning WHY valorisation in various parts of the world have been performed in the past. Onalenne Gwate is currently preparing a scoping review of the literature that will aid in the identification of a suitable strategy for Lake Chivero.
The opportunity of digestion or fermentation of WHY will be investigated during Onalenna Gwate’s 6-month research stay at IHE Delft, under supervision of Professor Piet Lens. In a laboratory setting, they will compare anaerobic digestion and lactic acid fermentation of collected water hyacinth biomass: yields, residue characterisation, process time, need for pretreatment, optimal C/N ratio, etc. The survival of pathogens during the anaerobic digestion and lactic acid fermentation of collected water hyacinth biomass, including faecal bacteria, viruses and plant parasites will be monitored.
Following the study, the anaerobic digestion and lactic acid fermentation of collected water hyacinth biomass will be optimised by modifying the water content and carbon to nitrogen (C/N) ratio by cofermentation of locally available nitrogen-rich biomass, e.g. chicken manure.
The findings from the laboratory will be tested on-site with small-scale pilot projects.
Figure 5.1. Water hyacinth from Lake Chivero. Photo by Marloes Penning de Vries.
A long-term WHY management strategy will be developed within WP 6 that addresses the needs of the various stakeholders and has its roots in scientific findings from all other WPs. The strategy will include adaptation, mitigation, and exploitation measures that will bring benefits to all stakeholders and ensure societal uptake beyond the lifetime of the project. The relevance of the strategy will be ensured by involving stakeholders in the creation process from the start. Moreover, including stakeholders in pilot projects and citizen science activities, clearly communicating decisions and keeping stakeholders informed of progress increases likelihood of them taking up and contributing to the successful implementation of developed strategies. It also allows the academic partners to gain broader perspectives and avoid scientific locked-ins.
Who: Timothy Dube, Marloes Penning de Vries, Carmen Anthonj, Onalenna Gwate, Thomas Marambanyika, Finn Münch, Mgcini Ncube, Ntandokamlimu Nondo, Frank Osei, Lisette de Senerpont Domis, Cletah Shoko, Daphne van der Wal
Three stakeholder consultation meetings are planned throughout the project: one at the beginning, one at midterm, and one at the end. The first stakeholder meeting was held on February 26, 2024; the second is tentatively planned to take place in February/March, 2026. The first workshop assessed the terms of reference of interacting and identify the various stakeholders’ needs and wishes. Based on a stakeholder mapping exercise, we invited communities, policymakers and numerous different types of stakeholders to a conversation on human, ecosystem and societal health around Lake Chivero. The meeting featured self-moderated break-up sessions in which topics were discussed amongst participants from a future-thinking perspective. For example: how do you want Lake Chivero to look in 30 years’ time? The findings of the workshop are currently being prepared for publication by PhD student Mgcini Ncube.
Figure 6.1. Group photo of participants of the stakeholder consultation meeting held in Harare, Zimbabwe, 26 February 2024.
This comprehensive training course is designed by Thomas Marambanyika to equip participants with essential knowledge and practical skills in water quality monitoring. The focus is on understanding the impact of water hyacinths on Lake Chivero and other water bodies. Also, sustainable solutions to enhance human and ecosystem health will be explored.
Participants will gain a thorough understanding of water quality parameters as well as detection of coliform bacteria as indicators for faecal-oral disease transmission and diarrheal disease occurrence, through interactive sessions and hands-on training. They will learn to measure these parameters using both traditional methods and advanced water quality sensors, including the maintenance and use of these sensors for reliable data collection. A key component of the course is the Water Hyacinth Dashboard application, which provides real-time data visualisation and analysis. Participants will receive training in using this application to monitor water quality, interpret data, and share findings with the community and scientific network.
At the end of the project, an international meeting, tentatively entitled “Strategies to improve human and ecosystem health in and around lakes of Southern Africa”, will be organised to discuss our findings and strategies with scientists from Africa and around the world. This ensures that our project’s various outputs, particularly the scientific articles and data sets, are known and can be used, applied, and improved by scientists working on aspects of sustainable lake management.
Our project will impact the health of the lake ecosystem and the well-being and living conditions for people relying on lakes and reservoirs. This will lead to increased resilience of the ecosystem and its resident communities. Specifically, we aim for three domains of impact:
By integrating scientific findings from satellite and empirical data from local communities with stakeholders’ perspectives and recommendations, we will contribute to more resilient lake socio-ecosystems. Linking the health of humans, animals, and their environment (like in the One Health approach) can be useful in mitigating and preventing water-related diseases. The mobile phone applications and the WHY management dashboard are schematically depicted in Fig. 2.4. Together with the WHY management strategies, the MSU undergraduate course, and citizen science projects developed within WP6, they form the main output of the project.
