Pervasive social and ecological water crises in Mexico remain, despite over two decades of legal and institutional backing for Integrated Water Resources Management (IWRM) as a policy tenet. In this article we apply a socialshed analysis to uncover and understand the geographical and jurisdictional forces influencing the social construction and simultaneous fragmentation of the San Miguel Watershed (SMW) in the state of Sonora, in Mexico's water-scarcity bulls-eye. Specific insights derived from an empirical analysis include that water management (WM) is socially embedded in dense networks of family and friends, farmers and ranchers, citizens and local government - all to varying degrees sharing information about local water crises. Irrigation water user representatives (WUR) are connected across communities and within their own municipalities, but interwatershed social links with other WUR are virtually nonexistent, despite high levels of awareness of crossmunicipality WM problems. Implementation of IWRM as a federal policy by a single agency and the creation of basin councils and subsidiary technical committees for groundwater management have not been sufficient for technical - much less social - integration at the watershed level. This study shows that the SMW socialshed remains fragmented by local jurisdictions; without coordinated agency-jurisdiction-local action fomenting social connections, a socialshed will not emerge.