The predominantly agricultural Mekong Delta region will be profoundly affected by the effects of climate change, such as rising temperatures, sea level rise, and salinization. But recent studies show that other factors, such as sand mining and groundwater exploitation, will also largely contribute to future pressures, particularly through land subsidence. Alongside the fight against climate change, this makes it necessary to design strategies and policies for subsidence mitigation, not only at the individual level (mainly farmers), but also at the institutional level (province and region). Indeed, in the Vietnamese Mekong Delta (VMD), local provinces play a crucial role in the choice and implementation of strategies for the exploitation of natural resources, such as water or sand. However, the VMD is also a complex system in which the decisions of one province can have indirect effects on the other 12 provinces, especially because some provinces share common agro-ecological regions and aquifer areas. This chapter aims to explore, through simulation of an integrated model, the economic impact on farmers of the adaptation strategies chosen by the provinces under a number of climatic and economic scenarios. It thus builds on the adaptation options evaluated in Part 3 of the report. In particular, one objective is to understand which conditions of inter-province coordination on groundwater exploitation in common agro-ecological areas could improve the economic situation of farmers. To this end, the LUCAS model (an agent-based model for land-use change adaptation strategies in the context of climate change) [ Truong et al.,2021 ] was extended to take groundwater use by farmers into account, as  well as the subsidence dynamics and macroeconomic trends from the GEMMES model. In the updated model, called LUCAS-GEMMES, subsidence-related adaptation strategies chosen at the provincial level and their interactions with individual decisions were also introduced. The simulation is performed with 4 experiments including (i) No provincial adaptation strategies and ignorance of subsidence dynamics; (ii) No adaptation strategies while subsidence impacts the benefit of land-use production; (iii) Individual adaptation strategies combined with the impact  of subsidence; (iv) Province and individual adaptation combine with the impact of subsidence. The results show that decisions in early response to low-level subsidence bring many positive results in resource management, such as  significantly reducing water use in the dry season, and reducing the vulnerability area from subsidence and climate  change. The results also show a decrease in incomes in case of adaptation. Therefore, it is necessary to have investment solutions (technical support in shrimp farming, studying for new upland crops in the dry season) for new land-use types that could compensate for the economic benefits lost when applying policies that restrict people in the use of resources.