El riego por goteo usa el depósito de agua.

In Spanish, nouns have grammatical gender. Here:

• riego is masculine, so it takes el
• depósito is masculine, so it also takes el

There is no deep logical reason in most cases—you usually have to learn the noun together with its article:

• el riego
• el depósito

A useful pattern is that many nouns ending in -o are masculine, though this is not a perfect rule.

Riego here is a noun, not a verb. It means irrigation or watering.

It comes from the verb regar = to water / to irrigate.

So:

• regar = to irrigate
• el riego = irrigation

In this sentence, el riego por goteo is the subject.

In riego por goteo, por means something like by means of or through.

So literally, the phrase is roughly:

• irrigation by dripping
• or irrigation through drops

This is the standard Spanish expression for drip irrigation.

So although por often means for, by, or through, here it is part of a fixed expression:

• riego por goteo = drip irrigation

Goteo is a noun that comes from gota = drop.

It refers to:

• dripping
• drip flow
• a dropping action

So in riego por goteo, the idea is irrigation that works by water dripping little by little.

Usa is the third-person singular present tense of usar:

• yo uso = I use
• tú usas = you use
• él / ella / usted usa = he / she / you use

The subject here is El riego por goteo, which is singular, so the verb must also be singular:

• El riego por goteo usa...

It can mean either, depending on context.

Spanish often uses the simple present where English might use either:

• uses
• is using

So usa can mean:

• uses
• is using

If Spanish wants to be very explicit about an action in progress, it can use:

• está usando = is using

But in a general statement like this one, usa is completely natural.

Because el depósito de agua is a direct object, and with things, Spanish normally does not use a preposition before the direct object.

So:

• usa el depósito = uses the tank/reservoir

Spanish only uses the so-called personal a with specific people (and sometimes animals or personified things), for example:

• Veo a María = I see María

But here the object is a thing, el depósito, so there is no a.

Spanish often uses the definite article el / la / los / las in places where English might or might not use the.

Here, el depósito de agua means:

• the water tank
• the water reservoir

Using el usually suggests a specific tank/reservoir that is known from the context.

If you said just depósito de agua without an article, that would usually happen in other structures, for example:

• Necesitan un depósito de agua = They need a water tank
• Tiene depósito de agua = It has a water tank

But in this sentence, el depósito de agua is the natural full noun phrase.

De + noun is very common in Spanish to describe what something is for or what type it is.

So:

• depósito de agua = water tank / water reservoir

This is the normal way to name it.

If you say depósito para agua, it sounds more like:

• a container for water
• with emphasis on its purpose

That is possible in some contexts, but depósito de agua is the standard, idiomatic label.

Yes. Depósito is a broad word and can mean things like:

• tank
• reservoir
• storage container
• deposit
• warehouse/storage space in some contexts

In this sentence, because of de agua, it clearly means a container or reservoir for water.

In Spain, depósito can also be used in other everyday meanings depending on context, so it is a flexible word.

Yes. Utiliza works very well here.

Compare:

• usa = uses
• utiliza = uses / makes use of

Utiliza can sound slightly more formal or technical, while usa is simpler and very common. In a sentence about irrigation systems, both are correct.

Yes, but the original order is the most neutral and natural:

• El riego por goteo usa el depósito de agua.

Spanish word order is flexible, but changing it usually changes the emphasis.

For example:

• El depósito de agua lo usa el riego por goteo.

This puts more focus on the water tank. The extra lo helps mark el depósito de agua as the object.

So yes, word order can change, but the original sentence is the straightforward default.

A simple pronunciation guide:

• riego ≈ RYEH-go
• goteo ≈ go-TEH-o
• usa ≈ OO-sa
• depósito ≈ deh-PO-si-to
• agua ≈ AH-gwa

A couple of useful notes for Spain:

• riego starts with a rolled or tapped r sound, depending on your accent and position
• g in goteo is a hard g because it comes before o
• depósito has the stress on pó

So the sentence stress pattern is roughly:

• El RIEgo por goTEo Usa el dePÓsito de AGua.