code: def _qmed_from_area(self):
          
          try:
              return 1.172 * self.catchment.descriptors.dtm_area ** self._area_exponent()  # Area in km²
          except (TypeError, KeyError):
              raise InsufficientDataError("Catchment `descriptors` attribute must be set first.")
docs: Return QMED estimate based on catchment area.
  
          TODO: add source of method
  
          :return: QMED in m³/s
          :rtype: float