Learn Hardcore Dutch: We houden altijd een kleine voorraad water in huis. - We always keep a small supply of water at home.

In Dutch main clauses the finite verb must occupy the second position (the “V2 rule”). Since we (the subject) is first and houden (the finite verb) is second, any frequency adverb like altijd follows right after the verb. So the order is:
1) Subject (we)
2) Finite verb (houden)
3) Adverb of frequency (altijd)
4) Object (rest of the sentence)

If you really wanted to start with altijd, you could—then houden still comes second:
“Altijd houden we een kleine voorraad water in huis.”
But in neutral word order with the subject up front, altijd follows the verb.

Why do we use houden here instead of hebben or bewaren? They all seem to translate as “to have” or “to keep.”

Each verb has its own nuance:

houden in the fixed phrase iets in huis houden means “to keep something in the house” as an ongoing stock.
hebben simply means “to have” without emphasizing storage or reserve.
bewaren is more formal and suggests “preserving” or “storing” (often for perishables).

For everyday talk about keeping a supply at home, houden is the most idiomatic choice.

What does een kleine voorraad literally mean, and why does kleine get an -e at the end?

Literally, een kleine voorraad means “a small supply.”
Dutch adjectives take an -e ending when they precede a singular de-word (common gender) with any article—definite or indefinite. Since voorraad is a de-word and we have “een,” the adjective must be kleine (not klein).

Why is there no article before water, like het water or een water?

Water is an uncountable (mass) noun. When you speak of it in general—“water” as a substance—you omit the article. If you need to specify an amount, you use a measure word: een liter water, drie liter water, etc. You only use het water when referring to a specific quantity or previously mentioned body of water.

Is voorraad countable or uncountable in Dutch? Could I say twee voorraden water?

Voorraad is a de-noun and can be countable in the sense of “one supply,” but you rarely pluralize it in normal speech. Saying twee voorraden water would sound odd unless you were talking about separate stockpiles in different places. Usually you just adjust its size (e.g. “een grotere voorraad”).

Why do we say in huis here? Couldn’t we just say thuis?

In huis houden is a set collocation meaning “keep in the house” or “maintain a reserve at home.” Thuis means “at home” more generally as an adverb. You could say We hebben altijd water thuis, but when you want to stress the idea of keeping a stock you use in huis houden.

What’s the difference between we and wij? Can I say Wij houden altijd een kleine voorraad water in huis?

Yes, you can. We is the unstressed, colloquial form of wij, which is used when you want to emphasize the subject or in more formal writing. Using Wij houden altijd… puts a bit more stress on “we” (as opposed to someone else).

Can I rearrange the sentence, for example by starting with altijd or in huis?

Definitely—just keep the V2 rule in mind. Examples:

Altijd houden we een kleine voorraad water in huis. (Emphasizes frequency.)
In huis houden we altijd een kleine voorraad water. (Emphasizes location.)

What about using a diminutive like voorraadje instead of voorraad?

You can say We houden altijd een voorraadje water in huis. The diminutive -je adds a friendly, casual tone and explicitly signals that it’s a small little supply.

Are there any other words I could use instead of voorraad?

Some alternatives:

reserve (you might even say reservevoorraad for extra clarity)
stock (an English loanword used informally by bilingual speakers)
However, voorraad remains the standard, most natural term in Dutch.