Nitrate pollution occurs usually as a result of agricultural practices (fertilizer). Intensive agriculture practices developed during the past century have helped improve food security for many people but have also added to nitrate pollution in surface and ground waters. New research has looked at water quality measurement over the last 140 years to track this problem in the Thames River basin. The Thames River catchment provides a good study example because the water quality in the river, which supplies drinking water to millions of people, has been monitored for the past 140 years, and the region has undergone significant agricultural development over the past century. The nitrate transport route as well as application use was studied for its net effects on the Thames.