La reserva de agua incluye agua embotellada.

Because reserva is a feminine noun in Spanish, so it takes la in the singular.

• la reserva
• las reservas

In this sentence, reserva means something like a reserve, supply, or stock.

Here, de links two nouns and shows what kind of reserve it is or what it consists of.

So reserva de agua means:

• a reserve of water
• a water supply
• a stock of water

This is very common in Spanish:

• botella de vino = bottle of wine
• vaso de agua = glass of water
• depósito de gasolina = petrol tank / gas tank

Because del agua would usually mean of the water, referring to specific water already identified.

But in reserva de agua, the phrase is more general and describes the type of reserve, so Spanish uses de agua without the article.

Compare:

• reserva de agua = water reserve / water supply in general
• la reserva del agua del hotel = the reserve of the hotel’s water

Because Spanish often leaves out the article when talking about something in a general, non-specific way, especially with uncountable nouns like agua.

So:

• incluye agua embotellada = it includes bottled water

This is similar to English, where we usually say includes bottled water, not includes the bottled water, unless we mean a specific bottled water.

If you said incluye el agua embotellada, that would sound more like it includes the bottled water — a specific one.

Because embotellada is an adjective, and it agrees with agua, which is feminine singular.

So:

• agua embotellada
• reserva limitada
• comida preparada

Even though agua sometimes appears with el in the singular, it is still grammatically feminine, so adjectives stay feminine:

• el agua fría
• el agua embotellada

Not el agua frío or el agua embotellado.

Good question. Agua is a feminine noun, but in the singular it often takes el instead of la when it comes directly before the noun, because it starts with a stressed a sound:

• el agua
• el águila
• el arma

This is done for pronunciation, to avoid la agua, which sounds awkward in Spanish.

But that only affects the article directly before the noun. It does not change the noun’s gender. That is why the adjective is still feminine:

• el agua fría
• el agua embotellada

In your sentence, there is no article directly before agua, so we simply get:

• de agua
• agua embotellada

Incluye is the third-person singular present tense of incluir.

So it can mean:

• he/she includes
• it includes
• you include (usted form)

In this sentence, it means it includes, referring to la reserva de agua.

A few useful forms:

• yo incluyo = I include
• tú incluyes = you include
• él/ella/usted incluye
• nosotros incluimos
• ellos/ellas/ustedes incluyen

Yes, very often. It is a close match to the English verb include.

Examples:

• El precio incluye desayuno. = The price includes breakfast.
• La entrada incluye una bebida. = The ticket includes a drink.

So incluye is a very useful verb and often works just as an English speaker would expect.

Yes, you could, but the nuance is slightly different.

• incluye = includes; it is part of what is provided or part of the package
• contiene = contains; it focuses more on what is inside something

So:

• La reserva de agua incluye agua embotellada suggests bottled water is one of the things provided in the water reserve/supply.
• La reserva de agua contiene agua embotellada sounds more like the reserve literally contains bottled water.

Both are possible, but incluye is often better when listing what is provided.

A simple pronunciation guide:

• agua ≈ AH-gwa
• embotellada ≈ em-bo-teh-YA-da

In standard Peninsular Spanish, ll is usually pronounced like y in many modern accents, so:

• embotellada sounds roughly like em-bo-teh-YA-da

The full sentence is roughly:

• la reh-SEHR-ba de AH-gwa een-KLOO-ye AH-gwa em-bo-teh-YA-da

Yes, but the normal, neutral order is:

• La reserva de agua incluye agua embotellada.

That is the most natural way to say it in ordinary Spanish: subject + verb + object.

You could move things around for emphasis in some contexts, but it would be less neutral. For a learner, the standard version is the best one to use.