In response to a need for enhanced water governance, water institution reforms are taking place around the world. Common among these reforms is a shift from monocentric to polycentric governance systems, bridging multiple scales of stakeholders through a mix of institutional arrangements. Benefits of a polycentric approach are commonly associated with higher performance in diverse contexts through better adaption to changing conditions, customized rules that meet local needs and a sense of trust amongst stakeholders. However, even though water reforms identify probable benefits from a polycentric approach, the ability to predict which type of institutional arrangement is likely to yield desired outcomes remains a challenge. This study applies the institutional resource regime framework and transaction cost economics to evaluate the current water regime in British Columbia and identify if an alternative water governance arrangement can promote sustainable outcomes through minimized transaction costs. First, I perform an assessment of the water regime in British Columbia from 1859 to 2016 to identify how and why institutions have changed over time. Second, I compare the perception of transaction costs associated with a watershed agency and a regional district alternative arrangement to the current system to identify if an alternative arrangement can improve coherence through more efficient organizational structures. Third, I assess the perceived transaction costs for a watershed arrangement from respondents in the Okanagan region compared the rest of the province. Data were collected through document analysis and 36 surveys and 5 semi-structured interviews with government officials. Results confirm a complex water regime in British Columbia. Transaction costs under both watershed agency and regional district alternative arrangements were perceived higher compared to the current system, in contrast to what the literature would suggest. In addition, perceived transaction costs do not significantly differ between respondents in the Okanagan region compared to the rest of the province suggesting no additional coherence associated with a watershed agency arrangement in the Okanagan basin. I conclude that the current system is evolving towards integration, but remains complex due to incomplete Aboriginal rights and title to water, jurisdictional and organizational fragmentation and undefined water yield quotas and water quotas.