The spelling of the word "rivero" can be explained using the International Phonetic Alphabet (IPA). The first sound in "rivero" is /ɹ/, which is the "r" sound in English. The next two sounds are vowels: /ɪ/ and /v/. These are the vowel sounds in "pit" and "vest" respectively. The fourth sound is a consonant, /ɛ/, which is the "e" sound in "bet". Finally, the word ends with the "r" sound again, /ɹ/. Therefore, "rivero" is spelled with an "r", two vowels, a consonant, and another "r".