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.

In this study, we characterize the snowmelt hydrological response of nine nested headwater watersheds in southeast Wyoming by separating streamflow into three components using a combination of tracer and graphical approaches. First, continuous records of specific conductance (SC) from 2016 to 2018 were used to separate streamflow into direct runoff and baseflow components. Then, diurnal streamflow cycles occurring during the snowmelt season were used to graphically separate direct runoff into quickflow, representing water with the shortest residence time, and throughflow, representing water with longer residence time in the soil column and/or regolith layers before becoming streamflow. On average, annual streamflow was comprised of between 22% to 46% baseflow, 7% to 14% quickflow, and 46% to 55% throughflow across the watersheds. We then quantified hysteresis at both annual and daily timescales by plotting SC versus discharge. Annually, most watersheds showed negative, concave, anti-clockwise hysteretic direction suggesting faster flow pathways dominate streamflow on the rising limb of the annual hydrograph relative to the falling limb. At the daily timescale during snowmelt-induced diurnal streamflow cycles, hysteresis was negative, but with a clockwise direction implying that quickflow peaks generated from the concurrent daily snowmelt, with shorter residence times and lower specific conductance, arrive after throughflow peaks and preferentially contribute on the falling limb of diurnal cycles. Slope aspect and surficial geology were highly correlated with the partitioning of streamflow components. South-facing watersheds were more susceptible to early season snowmelt at slower rates, resulting in less direct runoff and more baseflow contribution. Conversely, north-facing watersheds had longer snow persistence and larger proportions of direct runoff and quickflow. Watersheds with surficial and bedrock geologies dominated by glacial deposits had a lower proportion of quickflow compared to watersheds with large percentages of metasedimentary rocks and glaciated bedrock.