Learn Spanish (Latin America): A causa de la sequía, restringirán demasiado el agua. - Because of the drought, they will restrict the water too much.

Porque translates to "because" and needs to be followed by a conjugated verb (as in "because there is a drought"). A causa de means "because of" or "due to" and is followed by a noun phrase. In this sentence, it is followed directly by the noun la sequía (the drought).

Why doesn't demasiado change to demasiada to match the feminine word agua?

In this sentence, demasiado is acting as an adverb meaning "too much," and it describes the verb restringirán (how much they will restrict it). Adverbs never change their endings. If it were describing the water itself rather than the action (like "they have too much water"), it would act as an adjective and change to match the feminine noun: demasiada agua.

I thought water was a feminine word. Why does it say el agua?

Agua is indeed a feminine noun! However, because it starts with a stressed "a" sound, saying la agua would sound awkward as the two "a" sounds blend together. To make it easier to pronounce, Spanish uses the masculine article el. If you were to add an adjective, it would still show up as feminine, like el agua fría (the cold water).

Who exactly is restringirán referring to here since there is no subject pronoun like ellos?