Environmental flows are delivered by one or more discrete flow interventions (or watering actions) taking the form of releases from storages, restrictions on diversions, or diversion of water into alternate flow paths and off-stream habitats. Generally, hydrological and ecohydraulic responses are the first link in the causal chain leading to an ecological outcome. Like all ecological intervention monitoring, evaluating hydrological outcomes must address the methodological challenges of detection and attribution. Whilst these challenges may seem trivial for individual discrete watering actions such as pumping water into a wetland, there are serious challenges when hydrological targets are distant from the point of intervention and multiple actions are considered across a large river basin. This presentation discusses these challenges in the context of the Long Term Intervention Monitoring Program for the Commonwealth Environmental Water Office in the 2014-15 water year. We present the methods and outcomes of the commonwealth program including contributions to baseflows, flow freshes and wetland filling across the basin.