Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_name_81 (in_state_area VARCHAR, outlet VARCHAR, basin VARCHAR)

### Question ###
What is the in-state area with an outlet of South Platte River and Big Thompson river as the basin?

### Accurate SQL ###

SELECT in_state_area FROM table_name_81 WHERE outlet = "south platte river" AND basin = "big thompson river"