The source of Reykjadalsá is from the roots of the glacier Ok and it flows through Hálsasveit and Reykholtsdal by historical places like Reykholt and Deildartunguhver. It merges Flókadalsá and they have the same estuary into Hvítá shortly above Svarthöfði. The river total length is 38 km and it´s catchment area with tributaries is 290 km. Quite a bit of hot spring water used to fall into Reykjadalsá, but has reduced significantly with activation of Deiltartunguhver, for the District heating of Akranes & Borgarfjörður. Considerable fluctuations have been in the salmon fishing in Reykjadalsá, from being about 30 salmon and all the way up to 300. 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. Many good fishing spots/pools are in the river, one of the best known being Klettafljót that suits extremely well for fly fishing. Other pools to be mentioned are Mjóanesáll and Tunnufljót.