Vl. Backlund et al., EFFECT OF AGRICULTURAL DRAINAGE ON WATER-QUALITY IN HUMID PORTION OF PACIFIC-NORTHWEST, Journal of irrigation and drainage engineering, 121(4), 1995, pp. 289-291
Agricultural drainage first began in Washington State around 1830 and
in Oregon around 1840. The first efforts to drain soils for agricultur
al use began by constructing shallow ditches spaced 18-20m apart to re
move excess surface waters from croplands. Farming of poorly drained s
oils was done by these systems of beds until the 1930s. These beds int
erfered with the use of modern machinery and in the 1930s the establis
hment of beds was diminishing in favor of subsurface tile systems. Bet
ween 1930 and 1980 there was a substantial increase in subsurface-tile
-drainage activity, which peaked during the 1960s. Since 1985, install
ations of subsurface and surface drainage have gradually diminished, a
nd constuction of drainage systems has been limited to replacement of
failed or deteriorated systems. By reducing saturated soil conditions
through subsurface drainage, surface-water quality has benefited by re
ductions of nutrients and pesticides associated with surface runoff. W
ith the increase of agricultural (dairy) waste applications to croplan
d, additional research is needed to quantify the impacts of subsurface
drainage on ground- and surface-water quality.