Question: The River Ancholme in Lincolnshire in the east of England ends in which estuary?

Context paragraphs:
Horkstow Bridge: Horkstow Bridge is a suspension bridge that spans the New River Ancholme near the village of Horkstow in North Lincolnshire.  It was designed by Sir John Rennie as part of the River Ancholme Drainage Scheme, completed in 1836, and is a Grade II* listed building.

Worlaby: Worlaby is a village and civil parish in North Lincolnshire, England, 6 mi south-west from Barton-Upon-Humber and 5 mi north-east from Brigg.  The population of the civil parish at the 2011 census was 547.  It lies on the B1204, and to the east of the River Ancholme.  It is one of the five "Low Villages" – South Ferriby, Horkstow, Saxby All Saints, Bonby, and Worlaby – between Brigg and the River Humber, named so because of their position below the northern edge of the Lincolnshire Wolds.  Worlaby was previously part of South Humberside administrative district, and before that, the North Lindsey division of Lindsey, Lincolnshire.

Read's Island: Read's Island is an island situated just outside the Ancholme sluice, on the Humber Estuary in England.  The Lincolnshire Trust suggest it is an artificial island, and a report from 1979 says that it was reclaimed.  However, the site was for many years a large sandbank going by the name of "Old Warp" and is shown on the 1734 Customs Map of the Humber where Read's Island now lays, and extending further downstream.

River Rase: The River Rase is 16 mile (25km) long tributary of the River Ancholme that flows through Lincolnshire, in the east of England.

Ferriby Sluice: Ferriby Sluice is a hamlet situated near the lock complex on the Humber and River Ancholme, Lincolnshire, England.

Brigg: Brigg () is a small market town in North Lincolnshire, England, with a population of 5,076 in 2,213 households (2001 UK census), the population increasing to 5,626 at the 2011 census.  The town lies at the junction of the River Ancholme and east–west transport routes across northern Lincolnshire.  As a formerly important local centre, the town's full name of Glanford Brigg is reflected in the surrounding area and local government district of the same name.  The town's urban area includes the neighbouring hamlet of Scawby Brook.

River Ancholme: The River Ancholme is a river in Lincolnshire, England, and a tributary of the Humber.

Hibaldstow Bridge: Hibaldstow Bridge is an iron arch bridge that spans the River Ancholme, near the villages of Hibaldstow, in North Lincolnshire, and North Kelsey, in the West Lindsey district of Lincolnshire.  A plaque mounted in the centre of the bridge reads "Erected By JTB Porter & Co. 1889 Lincoln".

Horkstow: Horkstow is a village and civil parish in North Lincolnshire, England, 4 mi south-west from Barton-Upon-Humber, 1 mi south from South Ferriby and 9 mi north from Brigg.  It lies on the B1204, and 1 mi east from the navigable River Ancholme.  It is one of the five "Low Villages" - Worlaby, Bonby, Saxby All Saints, Horkstow and South Ferriby - between Brigg and the River Humber, so-called because of their position below the northern edge of the Lincolnshire Wolds.  Horkstow was previously part of South Humberside administrative district, and before that, the North Lindsey division of Lindsey, Lincolnshire.

Caistor Canal: The Caistor Canal was a 4-mile (6.4 km) canal in Lincolnshire, England, constructed between 1793 and 1798.  It fell into disuse sometime after 1850 and was legally abandoned in 1936.  It ran from the River Ancholme, near South Kelsey toward Caistor through six locks, terminating at Moortown, 3.5 miles (5.6 km) away from its intended terminus at Caistor.  Parts of it were dredged in 2010, to aid flood defences in South Kelsey.

Supporting paragraphs: Read's Island River Ancholme
Answer: Humber Estuary