It has a capacity of 20 million m³ at a depth of 2 m. Immediately to the south, where the artificially constructed conduit of the river Hase flows into the Alfsee lakes, there is a small auxiliary basin (Absetzbecken) in front of the actual reservoir, from which water flows into the lake via a roughly 330 m long overflow dam.

Roughly north of the town of Bramsche an artificial channel branches off the Hase that takes water from the south for about 4.5 km to the lakes of the Alfsee.

The water draining from the Alfsee runs over a similar artificial drainage channel, about 1.3 km long, directly west of the reserve basin north of the Alfsee, where it flows along the 2.5 km long canalised lower reaches of the Ueffelner Aue, which passes the Alfsee to the west running in a south to north direction west of Alfhausen, before flowing back into the Hase.

Today this has holiday homes, several campsites and sports pitches as well as a boating harbour with a sailing school and a waterskiing area.

As well as holiday makers and water sports enthusiasts, the Alfsee is popular with anglers, particularly because of the presence of tench.