Both vertical and horizontal hydraulic conductivities should be measured in the field before designing the system. High values of horizontal hydraulic conductivity creates the potential for lateral seepage. This allows for a wider drain spacing, which can reduce installation costs. However, losses from the edge of the field may be excessive under these conditions, especially if the adjoining field is drained. Water Supply Available water from a reliable source is a very critical factor for all types of irrigation.
Water is needed most during the driest parts of the growing season.
Streams are often unreliable, because flow rates decrease when water demand is highest. Wells, ponds, and reservoirs are used frequently for irrigation water supply. Net irrigation water requirements in the Midwest depend on crop, location, and weather. Irrigation to meet the evapotranspiration demand for a typical Ohio growing season may require as much as 5 gallons per acre per minute per day. The ability to drain rapidly when rainfall occurs during subirrigation periods is critical.