In the last decades, policy reforms, new instruments development, and economic resources investment have taken place in water sanitation in Mexico; however, the intended goals have not been accomplished. The percentage of treated wastewater as intended in the last two federal water plans has not been achieved. The creation of River Basin Commissions and the decentralisation process have also faced challenges. In the case of Tlaxcala, the River Basin Commission exists only on paper and the municipalities do not have the resources to fulfil the water treatment responsibilities transferred to them. This lack of results poses the question whether the context was sufficiently considered when the reforms were enacted. In this research, we will study the Tlaxcala Atoyac sub-basin, where water treatment policy reforms have taken place recently with a more context sensitive approach. We will apply the Governance Assessment Tool in order to find out whether the last reforms are indeed apt for the context. The Governance Assessment Tool includes four qualities, namely extent, coherence, flexibility, and intensity. The assessment allows deeper understanding of the governance context. Data collection involved semi-structured in-depth interviews with stakeholders. The research concludes that the observed combination of qualities creates a governance context that partially supports the implementation of the policy. This has helped to increase the percentage of wastewater treated, but the water quality goals set by the River Classification have not been achieved. With the last reforms, in this hierarchical context, decreasing the participation of municipal government levels has been shown to be instrumental for improving water treatment plants implementation policy, although many challenges remain to be addressed.