The Tiffin Watershed (HUC 04100006) covers approximately 670 square miles in north-central Ohio. It is primarily an agricultural watershed with some urban development. The topography is generally flat with several small streams flowing into the Sandusky River. The area experiences a humid continental climate with an average annual precipitation of 36 inches. The watershed receives most of its precipitation during the spring and summer months. The snowpack is typically minimal due to the relatively mild winters. Surface water quality is generally good, but agricultural runoff can cause elevated levels of nutrients and sediment. The largest reservoir in the watershed is Tiffin City Reservoir #1, which is used for drinking water. There are no notable trends in climatic data for the Tiffin Watershed.