The source of River Reykjadalsá is the Ok glacier and it flows through Hálsasveit and Reykholtsdal past historical places such as Reykholt and Deildartunguhver. The Reykjadalsá merges with River Flókadalsá and they have the same estuary into River Hvítá shortly above Svarthöfði. The river’s total length is 38 km and its catchment area with tributaries is 290 km. Quite a bit of hot spring water used to feed into Reykjadalsá, but has reduced significantly with activation of Deildartunguhver, for the District heating of Akranes & Borgarfjörður. There have been considerable fluctuations in the salmon fishing in Reykjadalsá, from about 30 salmon and up to 300 salmon. Breeding conditions have been good in the upper part of the river, while they have been worse in the lower part. This happens when the temperature is high on warm days, in drought summers. Reykjadalsá is a late summer river, at its best in late August or even in September. There are many good fishing spots, one of the best known being Klettafljót that is excellent for fly fishing. Other notable pools are Mjóanesáll and Tunnufljót.