oxbow lake eei

Life after cutoff

Understanding the physiochemical evolution of oxbow lakes

Project summary

The Challenge

Oxbow lakes support a wealth of ecosystem services yet we know little about how they attain and sustain their physical and chemical characteristics

The Approach

Measuring the physiochemical characteristics of oxbow lakes using a range of in-situ sensing approaches and sediment core and water chemistry analysis

The Outcome

We will quantify the spatial and temporal variability in oxbow lake physiochemistry and understand the key controls on these characteristics

Lead academics

Funded by

Project partners

Loughborough University

Universidad Autónoma del Beni 

The Challenge

Meandering river systems naturally mediate the flux of water, nutrients, and sediment through the landscape, attenuating floodwaters and filtering contaminants within the floodplain, while supporting a suite of floral and faunal species. However, the combined effects of climate change and land-use alteration will change the natural functioning of these environments, which will threaten the survival of riverine communities across the world.

Synonymous with meandering rivers are oxbow lakes – arcuate lakes formed by the termination of river bends as they collide into one another, or are bypassed by the river in favour of a shorter, steeper flow path. These lakes form specialist habitats for aquatic species and essential nutrient and contaminant filters, removing them from the river and burying them in the lake bed. Despite widespread knowledge of oxbow lakes as landforms, little is known about their physical and chemical characteristics, particularly in space and time. 

Understanding how the lakes function now is essential for learning how they will respond to changes in the future
Dr Josh Ahmed

Dr Josh Ahmed

Leverhulme Trust Research Fellow

To truly forecast how these aquatic systems will change in the future, we need to understand how they function now. Rivers in the Amazon Basin – particularly near the Andes mountain range in Bolivia – provide a unique opportunity for us to measure the physical and chemical characteristics of oxbow lakes in a relatively unaltered setting. Moreover, because these rivers evolve so quickly (migrating at 10s of metres per year, and creating oxbow lakes over annual to decadal timescales, we can observe the full evolutionary process; from inception to terrestrialisation, where the lake is completely filled and converted back to land.

The full research team

The Approach

The project is divided into two distinct phases: phase one is focused on understanding the controls on lake hydrology exploiting a 40-year satellite imagery archive to monitor and quantify water surface area changes through time and the key controls on this behaviour. Understanding the controls on lake hydrology will help identify the provenance of lake physiochemistry, thus allowing forecasts of how these characteristics may change in the future. Phase two is focused on field validation and measurement, collecting in-situ measurements of lake physiochemistry and reconciling measurements with remote sensing imagery to widen the findings to the catchment scale.

Josh Ahmed EEI Oxbow
Dr Josh Ahmed deploying sensors in the Amazon

Phase two will be undertaken by a multidisciplinary team of academics from Loughborough University, CIRA, and led by the Energy and Environment Institute. The team will explore three lakes on the Mamore River in Bolivia, collecting measurements of water chemistry, bathymetry, flow characteristics, and lake-bed sediment composition, to understand how these lakes develop their unique physiochemical characteristics. Every year, seasonal rainfall causes river water levels to rise, temporarily reconnecting the lakes back to the channel and allowing for the exchange of water, nutrients, sediments, contaminants, and wildlife. Measurements will be collected of water chemistry and flow velocity during this crucial mixing period to establish its effect on lake evolution.

The Impact

A deeper understanding of the processes controlling the evolution of these rich riparian habitats will enable us to protect them – and the communities they sustain – in the future, in both the Amazon, and across the world. Our measurements will reveal how lake physiochemistry varies across the lake and how these characteristics change seasonally. Combining these changes with the remote sensing analysis will allow us to predict how future changes in hydrology, driven by climate change and human modifications, will impact lake physiochemistry, and thus the communities they support,

Working with the Royal Geographical Society we will disseminate our novel findings to thousands of students through educational curricula, while communicating our findings to local communities through our project partners. The results will create a step-change in our understanding of oxbow lakes, allowing us to actively develop methods for protecting these habitats in the future.