Controlled Agricultural Drainage to Maintain Water Quality

Abstract

The effects of land clearing and drainage as well as effect of drainage system design and management upon hydrologic and water quality parameters were determined. The most dramatic effect of agricultural land development on hydrology is the 2–3 fold increase in peak runoff rates. However, there is little effect upon total water efflux. Land clearing for agriculture does significantly increase N and P efflux in drainage water with the magnitude of the increase being dependent upon soil type. Design of the drainage system, particularly with regard to drain spacing and intensity of surface drainage, can have a large influence upon the proportion of outflow that occurs via surface runoff which is fast and that which leaves the field more slowly via subsurface flow. Improvement of subsurface drainage can result in a 10‐fold increase in the