An intestinal hormone that stimulates the pancreas to release watery secretion that is rich is bicarbonate ions is

The intestinal hormone that stimulates the pancreas to release a watery secretion that is rich in bicarbonate ions is secretin. 

Secretin is a hormone produced by the small intestine, specifically in the duodenum. Secretin is released when acidic chyme from the stomach enters the duodenum. Secretin then acts on the pancreas to stimulate the release of a bicarbonate rich fluid into the small intestine. This bicarbonate-rich fluid helps neutralise the acidic chyme from the stomach, creating a suitable pH environment for the action of digestive enzymes in the small intestine.

(1) Gastric inhibitory peptide (GIP) is a hormone released by the small intestine in response to the presence of nutrients, especially glucose and fat, in the digestive tract. GIP helps inhibit gastric acid secretion and slows down gastric emptying to allow for proper nutrient absorption.

(2) Enterokinin (enterocrinin) is a hormone secreted by the duodenum, and its primary function is to activate crypts of Lieberkuhn.

(4) Cholecystokinin (CCK) is a hormone produced by the small intestine in response to the presence of fatty acids and amino acids in the duodenum. CCK stimulates the gallbladder to release bile, which aids in the digestion and absorption of fats. It also simulates the secretin of pancreatic enzymes.