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The US Midwest is expected to experience higher intensity rainfall events along with an increased chance of drought during the mid- and late 21st century under projected future climate scenarios. Development of strategies to mitigate the impact of these projected changes on agricultural production and environmental quality is important for ensuring agricultural resiliency to future climate. This study used the DRAINMOD hydrologic model to simulate subsurface drainage discharge at a field site in the headwaters of the Western Lake Erie Basin using future climate patterns projected by 20 general circulation models. Despite projected increases in rainfall, by the late twenty-first century, subsurface discharge was projected to decrease 7% and 11% under representative concentration pathway (RCP) 4.5 and RCP 8.5, respectively. Reductions in subsurface discharge were attributed to increased temperature and evapotranspiration. The performance of controlled drainage was not projected to change on an annual basis throughout the next century. The benefits of controlled drainage systems as an agricultural best management practice were still evident under the projected climate change of the next century. The role of controlled drainage as a means to potentially retain more crop available water in the soil profile could become critically important under future climate conditions. [ABSTRACT FROM AUTHOR]

Water quality research and monitoring programs often form the basis from which related legislation is derived. Yet, no standard, protocol, or method is available for guiding the selection of a water quality sampling strategy for runoff from fields and small watersheds. The objective of this study was to develop a methodology that provides guidance in the selection of a water quality sampling strategy for headwater streams (drainage areas less than 2500 ha; 6,177 ac). The developed method is based on the dimensionless unit hydrograph and relationships of measured pollutant concentrations to discharge hydrographs. The methodology was designed for storm events with a specific return interval and a selected acceptable level of error in pollutant load. Nine input parameters (hydraulic length, watershed slope, curve number, drainage area, runoff coefficient, 10-year, one hour precipitation amount, 100-year, one hour precipitation amount, 10 year, 24 hour precipitation amount, and recurrence interval) were used to develop the design hydrograph. Both time- and flow-paced sampling techniques were considered. A global sensitivity analysis of the method indicated that time-paced sampling was primarily sensitive to parameters included in the time of concentration calculation (hydraulic length, watershed slope, and curve number). Flow-paced sampling showed some sensitivity to all nine input parameters. An example application illustrates the utility of the method. Use of the method should facilitate the selection of water quality sampling strategies for field and small watershed scale studies and aid in budgetary planning for sample collection and analysis. The measurements taken based on the recommended sampling strategy will provide more confidence in the pollutant storm load estimates. [ABSTRACT FROM AUTHOR]

Impacts of watershed scale conservation practice adoption on sediment, nutrient, and pesticide losses and adjacent stream biota are not well understood. The objective of this study was to examine the suitability of selected paired watersheds to quantify hydrology, chemical, and ecology effects of conservation practice implementation for channelized and unchannelized watersheds in Upper Big Walnut Creek watershed, Ohio. Channelized watersheds were more similar in watershed characteristics than the unchannelized watersheds. One hydrology, eight water chemistry, and five fish community response variables were measured. Most response variables in both watershed pairs were moderately correlated (r > 0.6), but the minimum percent change required to detect a response difference was greater for the unchannelized watersheds. Detectable temporal trends in the difference between like response variables for the channelized and unchannelized watershed pairs were minimal. These results validate the paired watershed design and suggest that conservation practice induced changes in hydrology, water quality, and fish communities can be quantified. [ABSTRACT FROM AUTHOR]

Recent evidence suggests that turfgrass nutrients in runoff and subsurface flow pose potential risks to surface water quality. Research on water quality associated with turfgrass has generally focused on surface runoff, not subsurface flows. Quantifying the delivery of nutrients, nitrate nitrogen (NO3-N) and dissolved reactive phosphorus, to streams from subsurface drainage features on managed turf sites, and relating the transport to fertility management and season is important for many urban managers, especially those under regulatory scrutiny. NO3-N and dissolved reactive P concentrations from two French drains located on the Morris Williams' Municipal Golf Course in Austin, Texas, were measured over a four-year period (March, 1999 to March, 2003). Time series statistics were used to analyze and relate NO3-N and dissolved reactive P concentrations to weather and management. A weak statistical relationship (r² = 0.55) was detected between discharge and NO3-N concentration at one of the two drains. The relationship between discharge and dissolved reactive P concentration was not significant. Median NO3-N concentrations from the two drains were 1.27 mg L-1 and 0.32 mg L-1 NO3-N loading from the drains was 2.7 kg ha-1 (2.4 lb ac-1). The NO3-N concentrations and load from the turf area were approximately 10 percent of those values reported for typical row crop agriculture. Median dissolved reactive P concentrations were o.11 mg L-1 and 0.09 mg L-1 while dissolved reactive P loading was 0.46 kg ha-1. Significant (α = 0.05) seasonal tendencies were found with respect to NO3-N and dissolved reactive P. A strong correlation was evident between the timing of peak NO3-N losses and nitrogen application; and between the timing of peak NO3-N losses and air temperature. There was a similar correlation between the timing of peak dissolved reactive P losses and phosphorus application. Our results suggest NO3-N transport in subsurface drainage from this golf course is not a water quality issue. However, our findings suggest significant dissolved reactive P transport through the drains and a need for an integrated (turf, nutrients, and water) management plan that includes consideration of subsurface drainage fluxes. [ABSTRACT FROM AUTHOR]