Over 85% of the water delivered to AWWU customers comes from Eklutna Lake, nestled high in the mountains of Chugach State Park. Most of the lake water is diverted through a mountain tunnel and penstock to the Eklutna hydroelectric facility located on the Old Glenn Highway north of the lake. AWWU takes a small portion of that water for Municipal Water Supply.

The lake outflow is relatively constant over the year, while inflow is dominated by summer melting of snow and glacier ice. As a result, the water level in the lake varies by as much as 60 vertical feet from a low in spring to a high level in the fall, following the summer melt season. Maximum lake level is controlled by a weir at elevation 871 feet above mean sea level.

Lake levels are monitored by the United States Geologic al Survey. Current lake levels, as well as temperature and precipitation data, are posted on the USGS website.