May one recite a blessing upon dipping his hands in a river?[1]
If the river is an invalid Mikveh [i.e. made of rainwater[2]] then one may not say a blessing over the washing until he pours the water on his hands.[3] If however the river is considered a valid Mikveh [i.e. made of spring water[4]] then one may dip his hands with a blessing, and then re-wash again later, as explained in the next Halacha.[5] A typical river is made of spring water and is hence valid for the blessing.[6]
[1] This follows the ruling of Admur in the Siddur which equates the laws of the morning washing to the laws of washing for bread. However, according to Admur in Kama 4:2 and the other Poskim [Michaber ibid; M”A ibid] a blessing may always be said over dipping the hands in a river for the morning washing and this ruling here is only relevant in a case that one is washing for bread.
[2] Yoreh Deah 101:2; If it is made of majority rainwater and minority spring water then according to the Ashkenazi custom one may dip with a blessing. [Rama ibid; Ketzos Hashulchan 34 footnote 2] However according to the Michaber ibid one may not say a blessing. [Kaf Hachaim 159:84] If it is made of majority spring water according to all it is a valid Mikvah and a blessing may be said. [ibid]
[3] 159:22 regarding washing for bread in moving rainwater. There Admur rules that it is questionable whether it is valid, and hence a blessing should not be said due to Safek Brachos Lihakel. Now, the Siddur states that morning washing follows same laws as washing for bread and hence also regarding the morning washing no blessing is recited; An additional reason and source is from Basra 4:2 which states:“only purified if one pours on them”. This implies no impurity is removed through pouring and hence a blessing may not be recited as according to Basra [and Siddur] the removal of impurity is part of the reason behind the blessing [see previous footnotes for explanation]
Ruling of Siddur: In the Siddur Admur does not mention whether one may dip his hands in a river and rather simply states that if a vessel is not available one may dip his hands in a Mikvah and recite a blessing and if he then finds a vessel he is to rewash properly.
[4] See previous footnotes regarding if it is majority rainwater.
[5] As stated in the next Halacha regarding dipping in a Kosher Mikvah, and so rules Ketzos Hashulchan 34 footnote 2 regarding washing for bread.
[6] Ketzos Hashulchan 34 footnote 2; Piskeiy Teshuvos 159:23 regarding washing for bread.