Final answer:
Nepal has been divided into seven provinces according to the 2015 constitution, not particularly based on rivers but with rivers marking some boundaries.
Step-by-step explanation:
The country of Nepal has been divided into seven provinces or states which were formed by grouping the existing districts; this division is not based specifically on the distribution of rivers, but rivers do play an important role in delineating the provinces to some extent. In 2015, a new constitution was adopted, which led to the creation of these provinces as part of a federal system of government. Each province has its own government and certain autonomous powers.