Gnomish
nen(n)
noun. water; river
asc
noun. water
sîr
noun. river
There are more words but they are from Tolkien's earlier conceptional periods. Tolkien likely changed these words as he evolved the aesthetics and completeness of the languages. You may even find languages that Tolkien later rejected. Do not mix words from different time periods unless you are familiar with the phonetic developments.
Below: Tolkien's Late Period (1950–1973). These are from Tolkien's late conceptual period — his most settled forms of the languages. Prefer these over the earlier ones above when composing new text.
A noun glossed “water” appearing in the Official Name List for the Lost Tales of the 1910s, probably based on the early root ᴱ√ASAKA which was used for words meaning “waterfall” (PE13/101).