Assessing human impacts on the Red River system, Vietnam, to enable sustainable management

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The Red River in Vietnam is located in a rapidly developing area of the world's 13th most populous country. The area, which supports 20 million inhabitants, includes a major rice-growing region, the mega-city of Hanoi and a range of industries each of which have expanded in recent decades. The Red River Delta (RRD) delta area of the river which discharges water into the Bay of Tonkin provides crucial ecosystem services including the retention and removal of nutrients and pollutants for groundwater (drinking water) and marine resource protection, carbon processing, flood protection which is heavily managed through a series of agricultural dikes and sediment transport which governs erosion and deposition at the vulnerable coastal zones. However, hydropower dam installation, increasing agricultural fertilizer use, increases in urban wastewater and use of a range of toxic contaminants threaten these ecosystem services and the health and wellbeing of the people who live in this region. The delta region is a complex and highly modified hydrological network which is difficult to model using calibrations developed on more straightforward river basins from temperate regions. Therefore, this proposal aims to improve modelling capabilities through the application of the alternative approach of Materials Flow Analysis which is more suited to complex systems. The project focuses on filling in knowledge gaps in understanding on relationships between hydrology, nutrients, carbon and pollutants in the RRD region for improved model calibration using a combination of stable isotope and organic geochemistry techniques which have rarely been applied in this area. The first part of the project will use stable isotopes of oxygen and hydrogen to quantify precipitation-surface water- groundwater interactions and estimate the extent of saline intrusions upstream from the coastal zone. The second work package will focus on understanding how dam installation alters nutrient and carbon sequestration and removal from the downstream river in order to better inform reservoir management. The third work package will aim to better constrain nutrient cycling in the delta (including carbon, nitrogen, phosphorus and silicon) through the use of stable isotope techniques. The work will be supported by a PhD student project using more recently developed techniques of dual nitrogen isotope analysis (analysing N and O atoms in nitrates) and the application of Silicon-30 which can provide important information on silica cycling, shown to be important in rice paddy areas. The final work package will focus on providing an updated assessment of toxic contaminants from this region because systematic monitoring has not been conducted recently. A broad suite of persistent organic pollutants and heavy metals will be analysed, with a focus on some problem chemicals in this region such as the pesticide DDT and its derivatives which was banned in 1995 but has increased after that time indicating illegal usage, and the dioxin herbicide defoliant "Agent Orange" which was used extensively in the Vietnam War. For the first time we will measure pharmaceutical residues in river sediments and suspended particulates in order to evaluate the distribution and trends of these compounds across the delta. The project will also install facilities for "Microtox" analysis in Vietnam, allowing rapid screening for toxic pollutants in order to pilot the use of this technique for environmental monitoring agencies. The outputs from this project will deliver improved capabilities for MFA modelling of nutrients and hydrology, the carbon budget, the first measures of emerging pollutants (pharmaceuticals), updated measures of legacy and persistent contaminants and a newly establish national capability for toxic pollutant screening.