I. Praising for the Rivers
We praise God for the daily blessings He bestows on us. But we must also, the Talmud instructs us, praise Him for His marvelous creations. When you see mountains, valleys or rivers you recite the blessing praising He “who made the act of Creation” (Berakhos 54a). The wonder we experience at seeing such awe-inspiring parts of nature leads to praising God with a special blessing.
But how many people today really feel that way? We see rivers and mountains all the time. We travel the world and see much more incredible natural wonders than the valleys and seas near us. Should we still say this blessing?
II. Not All Rivers
Tosafos (ad loc., sv. al) argues that the blessing on rivers only applies to the four rivers listed in Genesis 2. However, Shulchan Arukh (Orach Chaim 228:2) seems to reject this view. The Magen Avraham (228:3) adopts a slight variation on Tosafos’ view. He rules that we only recite the blessing on big rivers, like those listed in Genesis. Arukh Ha-Shulchan (ad loc., 2) follows this approach, as does Mishnah Berurah (ad loc., 4) who adds that the rivers must be ancient. Shulchan Arukh (ibid.) adds that the river’s flow must remain natural, not having been artificially deviated by man.
Another ruling of Tosafos is also relevant. Tosafos (Berakhos 57b sv. ha-ro’eh) states that these types of blessing are not recited by people who regularly see the objects generating the practice. Someone who has seen a river within the past 30 days may not recite the blessing. The Eliyahu Rabbah (cited in Mishnah Berurah 224:3) goes even further and rules that someone who lives in a place where the objects are common does not recite the blessing even if he has not personally seen it recently. Since such a sight does not invoke wonder to residents, he presumably also is unafffected.
III. Not All Sightings
R. Simcha Rabinowitz (Piskei Teshuvos 228:2) argues that we do not normally recite the blessing on rivers because their flow may have been artificially deviated (based on Responsa Be-Tzel Ha-Chokhmah 2:10). However, R. Eliezer Melamed (Peninei Halakhah, Berakhos, Harchavos 15:4) points out that the above Magen Avraham implies we recite the blessing on big rivers, even without specific knowledge about their origins. Additionally, he asks, why were the Sages of the Talmud unworried about this concern? How would they know whether the rivers they saw had been artificially deviated?
Instead, R. Melamed (Peninei Halakhah, Berakhos 15:4) distinguishes between seeing and viewing. When driving past a sight, particularly when commuting, you generally focus on your destination rather than your environment. You barely even notice your surroundings, much less feel inspiration from them. On such a sighting you do not recite the blessing.
However, when hiking or sightseeing you engage with nature. You look around at the world and experience its beauty and wonder. On viewing a river in such a circumstance (and barring other detailed conditions such as the above), you recite the blessing even if you personally are not impressed. When in a context of appreciating nature, you bless its Creator.
R. Asher Bush (Sho’el Bi-Shlomoh, no. 10) adopts a different approach. He points out that the blessing is optional (based on Eruvin 40b). People today generally only recite the blessing on remarkable sights, such as Niagara Falls. If seeing a particular river (taking into account the various details) inspires you, then recite the blessing. If not, it is up to you since the blessing is optional.