The moisture regime of the natural soil is thought to be the most important attribute affecting vineyard establishment and maintenance (Roach and Arnold 1971). Drainage is influenced by many factors including texture, depth to imprevious layer, slope and landscape position. Additional inferences can be made about soil permeability, runoff and seasonably high water tables. There are 4 basic hydrologic classes A to D, with A being the best drained and D being the least. There are large areas in the county that are poorly drained, especially in the south. Most of the well drained soils are in the middle or northern parts of the county. There are small pockets of well drained soil along both lake shores.
| Hydrologic
Soil Group |
Criteria for placement in hydrologic soil group |
| A | Saturated hydraulic conductivity is very high or in the upper half of high and the internal free water occurance is very deep. |
| B | Saturated hydraulic conductivity is in the lower half of high or in the upper half of moderately high and the internal free water occurance is deep or very deep |
| C | Saturated hydraulic conductivity is in the lower half of moderately high or in the upper half of moderately low and the internal free water occurance is deeper than shallow. |
| D | Saturated hydraulic conductivity is below the upper half of moderately low and the internal free water occurance is shallow or very shallow and transitory through permanent. |