Abstract
Artificial subsurface (tile) drainage is used to increase trafficability
and crop yield in much of the Midwest due to soils with naturally poor
drainage. Tile drainage has been researched extensively at the field
scale, but knowledge gaps remain on how tile drainage influences the
streamflow response at the watershed scale. The purpose of this study is
to analyze the effect of tile drainage on the streamflow response for 59
Ohio watersheds with varying percentages of tile drainage and explore
patterns between the Western Lake Erie Bloom Severity Index to
streamflow response in heavily tile-drained watersheds. Daily streamflow
was downloaded from 2010-2019 and used to calculated mean annual peak
daily runoff, mean annual runoff ratio, the percent of observations in
which daily runoff exceeded mean annual runoff (TQmean), baseflow versus
stormflow percentages, and the streamflow recession constant.
Heavily-drained watersheds (> 40 % of watershed area)
consistently reported flashier streamflow behavior compared to
watersheds with low percentages of tile drainage (< 15% of
watershed area) as indicated by significantly lower baseflow
percentages, TQmean, and streamflow recession constants. The mean
baseflow percent for watersheds with high percentages of tile drainage
was 20.9 % compared to 40.3 % for watersheds with low percentages of
tile drainage. These results are in contrast to similar research
regionally indicating greater baseflow proportions and less flashy
hydrographs (higher TQmean) for heavily-drained watersheds. Stormflow
runoff metrics in heavily-drained watersheds were significantly
positively correlated to western Lake Erie algal bloom severity. Given
the recent trend in more frequent large rain events and warmer
temperatures in the Midwest, increased harmful algal bloom severity will
continue to be an ecological and economic problem for the region if
management efforts are not addressed at the source. Management practices
that reduce the streamflow response time to storm events, such as buffer
strips, wetland restoration, or drainage water management, are likely to
improve the aquatic health conditions of downstream communities by
limiting the transport of nutrients following storm events.