Worldwide, water resources are increasingly under pressure. The Water accounting approach of the System of Environmental-Economic Accounting (SEEA) has been developed to inform decision-makers on water supply, use, and quality. However, a critical issue in water accounting is finding data and models to populate SEEA water accounts. In particular, there are challenges in aligning hydrological models with accounting principles. Also, there is a need to test further how the SEEA water accounts can be connected to policy uses. The objective of this study is to develop water accounts with the use of a hydrological model. Specifically, we apply the SWAT hydrological model in the Buyuk Menderes Basin in Turkey to estimate the key hydrological parameters required for water accounting. To adapt and link SWAT to SEEA water accounts, we develop supply and use tables and asset accounts following the SEEA water for the year 2014 and explore how water accounts can inform policymaking. This article provides new insights into the added value of using a hydrological model in constructing water accounts for better water resources management.