Ipnu Rivulet — ruling 1

If a Desert has an ability with a cost of "Sacrifice a Desert," you can sacrifice that Desert to pay the cost for its own ability.

Ipnu Rivulet — ruling 2

Desert is a land subtype with no special meaning. It doesn't grant the land an intrinsic mana ability. Other cards may care about which lands are Deserts.

Ipnu Rivulet : règles, fonctionnement et interactions (MTG)

Ipnu Rivulet is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

: Add . , Pay 1 life: Add . , , Sacrifice a Desert: Target player mills four cards. (They put the top four cards of their library into their graveyard.)

How it works : Ipnu Rivulet

Original English text — Wizards of the Coast / Scryfall

#1July 14, 2017· Wizards of the Coast
If a Desert has an ability with a cost of "Sacrifice a Desert," you can sacrifice that Desert to pay the cost for its own ability.
No other card is named in this ruling.
#2April 18, 2017· Wizards of the Coast
Desert is a land subtype with no special meaning. It doesn't grant the land an intrinsic mana ability. Other cards may care about which lands are Deserts.
No other card is named in this ruling.