We have developed a simple method of illustrating river flow quantity using an index at 21 stream gauging stations across Alberta. The challenge was developing a comparable method to assess the relative flow conditions in rivers that range from essentially natural to those that are regulated by structures or subject to large abstractions or both. The recorded data is not directly comparable due to the varied mixture of both climatic and anthropogenic effects in observed flows between natural and managed systems. The indicator is based on the assumption that a natural average flow regime is defined to occur about 90 per cent of the time; and during the other 10 per cent of the time, the river regime will be naturally at an above average or below average state. Based on the indicator, the longer- term trend for most rivers in Alberta is normal (within historic natural range). However, many major rivers in southern Alberta during the summer are below normal or stressed. The Belly, Waterton, St. Mary and lower Bow rivers are most severely affected by flow regulation and water withdrawals in May to September to support irrigation. The occurrence of long-term below normal rankings in the Oldman and South Saskatchewan Rivers also indicates a cumulative human impact, although not to the same degree as their tributaries. Impacts of flow regulation for hydropower production are observed in the Bow River above Calgary, the North Saskatchewan River, and especially the Peace River. The Athabasca, Beaver, Clearwater, Hay, Pembina and Smoky Rivers are considered essentially natural; this means they are free of significant withdrawals and flow regulation.