Climate change and human-induced influences are threatening the Mekong Delta. Private wells and excessive use of groundwater have caused the water table to drop, the land to sink and fresh water resources to be lost through salinisation. These are the issues that scientists from four KIT institutes are looking to tackle in the CLIENT II project "ViWaT-Engineering". Working with local partners, they are developing concepts, strategies, and measures to stop these processes that ultimately threaten living conditions in the region.

Economically, the Mekong Delta is an very important region for Vietnam. The study area of the Ca Mau Peninsula is one of the most important rice growing and shrimp breeding areas in the country. However, due to climate change and human influences, the delta in its current form and function is threatened. Intensive overexploitation of groundwater has led to a sharp drop in groundwater levels and progressive land subsidence. In conjunction with the continuing rise in sea levels, this has been followed by rapid land loss in coastal areas. "These processes are accompanied by increasing salinisation of surface waters and groundwater," says Dr. Nicolas Börsig from the Institute of Applied Geosciences at the Karlsruhe Institute of Technology (KIT). This endangers the quality and regional availability of existing water resources.

From characterising water quality and land subsidence processes, ecosystem assessment and water demand analysis, to concepts for water treatment, further training of specialists and the development and construction of coastal protection measures, the Karlsruhe scientists from four KIT institutes – in cooperation with German companies and local partners – are taking a broad approach to develop sustainable coastal protection and water management in the research project "ViWaT-Engineering".

The project is focused on developing and implementing sustainable strategies, concepts, and technical measures to counteract the negative development in southern Vietnam. "The land subsidence is serious", says Börsig: "In some areas it is happening at a rate of more than two centimetres per year while the area is only about one metre above sea level". This is also clearly visible on roads or buildings, which now have structural deficiencies. In addition, the groundwater level continues to fall – also due to many private wells.

The first technical implementation measures are underway, despite COVID-19

Thanks to a KIT doctoral student on site who travelled to his family in Vietnam – and from there to the project area – the scientists in the working group have been able to remain in constant exchange via chat and video conferences – and be quasi "on site". Despite the effects of the COVID-19 pandemic, it was therefore possible to start the drilling for a first 235-metre deep groundwater well for monitoring water quality. Further wells will follow. These will be integrated into the existing monitoring network of the Vietnamese authorities, "to a certain extent extending the network of measuring points", explains Börsig: "This will also enable us to identify at what depth groundwater of what quality is present and draw conclusions about which areas are affected and how". After all, the Mekong Delta – larger than Baden-Württemberg – is a huge labyrinth of rivers, canals and swamps, in which over 20 million people live – between floating markets and rice fields. "Water is there", says Börsig, "life also takes place on the water – but the quality of the water is crucial".

Forecasting models are being developed from the data

In addition to developing coastal protection measures, one of the main objectives of the project is to gain a comprehensive insight into the temporal and spatial dynamics and variability of surface and groundwater quality. On the basis of the newly acquired and existing data from the Vietnamese partner organisations, prediction models will be developed, "with the help of which forecasts of future developments can be made and those areas can be identified which are severely threatened by inadequate groundwater quality or quantity", Börsig emphasises: "This is helped, among other things, by the newly established groundwater measuring points which enable the continuous and high-resolution measurement of salinisation and relevant water parameters such as pH value, oxygen content and redox potential".

The concepts and guidelines developed in the research project for sustainable use and supply through alternative water resources instead of groundwater can also be specifically adapted to regional conditions. Possible options here are the treatment of surface water, the remote supply through the Mekong or the local storage of rainwater for the dry season. At the same time, the methods developed and knowledge gained can also be transferred to other regions in Vietnam and comparable delta regions worldwide.