Salt intrusion: Understanding the Pearl River Estuary by Modelling and field Experiments (Newton Fund – SUPREME)

Saltwater intrusion in deltas and estuaries results from the complex interaction between water and salt dynamics, and is affected by climate change and human intervention. In the Pearl River Estuary (PRE) in China, these changes endanger freshwater availability affecting over 40 million people.

PRE’s complex shape (geometry and bathymetry) makes salt intrusion processes inherently three-dimensional. However, as previous research was mainly restricted to longitudinal variability, current knowledge is insufficient to unravel the interwoven longitudinal and lateral salt transport mechanisms.

The overall aim of the SUPREME project is to understand these three-dimensional salt transport mechanisms, and their sensitivity to variations in external forcing and local geographic shape. The knowledge and tools developed/applied in this project will help assess the effectiveness of possible measures to alleviate undesired changes in salt intrusion.

We adopt an integrated approach, involving both idealized and numerical modelling, as well as field measurements and data analysis. Idealized models include the essential physics and large-scale geometrical/bathymetrical features in a schematised way. Thus, they are specifically geared to clarify the interactions between governing physical mechanisms. Complex numerical models extend these results to transient forcing conditions and provide site-specific information. The combination of these two approaches provides insight, motivated and validated by new field measurements and existing data.

This joint project between the Netherlands, China and the UK presents a new integrated framework to understand salt dynamics in the PRE and other estuaries. It further provides a more solid scientific basis for estuarine management to prevent damaging saltwater intrusion in these regions. In order to provide more generic and global outlook and applicability to our work, we will compare salt intrusion in the PRE to salt intrusion in two other estuaries: the Mersey (UK) and the Ems (Netherlands/Germany).

The UK contribution of the project will be delivered by the National Oceanography Centre. The main focus of the UK research effort will be to develop and implement a state-of-the-art unstructured grid, numerical model of the PRE and other study areas. This numerical model will be used to conduct prognostic and diagnostic investigations. We will review a range of scenarios of future climate change and human interventions (e.g., sea level rise, river runoff, dredging, and freshwater abstraction). The UK contribution will also include long-term observations for the Mersey estuary, which will act as a pilot study for low-cost, long-term monitoring of salt intrusion in an estuary, thus providing proof-of-concept for a framework, which will be broadly applicable to other estuarine and deltaic systems in the world, including the PRE.