The boundary of the district in the west borders the River Trent, and meets Nottinghamshire (Bassetlaw) and North Lincolnshire at East Stockwith, close to Wildsworth. On the other side of the Trent is Gunthorpe, Lincolnshire. It deviates from the Trent, to the east along the River Eau at Scotter, where it meets Messingham in North Lincolnshire. The boundary deviates southwards near Scotton, then at Northorpe follows the B1205 eastwards, crossing the A15 at Waddingham. It follows the Sallowrow Drain to the Old River Ancholme at South Kelsey, which it follows northwards. At North Kelsey, it deviates from the Old River Ancholme, following the North Kelsey Beck eastwards. This crosses the B1434 then the Newark-Grimsby railway line, where at Searby cum Owmby it follows a drain parallel to the railway line northwards, and at Bigby it follows Kettleby Beck westwards across the railway line back to the Old River Ancholme, which it follows for almost a mile towards Brigg. The Bigby parish is the northern part of West Lindsey that skirts the southern edge of Brigg, crossing the A1084 and the railway line.