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ARS Home » Midwest Area » St. Paul, Minnesota » Soil and Water Management Research » Research » Publications at this Location » Publication #330319

Title: Open inlet conversion: Water quality benefits of two designs

item Feyereisen, Gary
item FRANCESCONI, WENDY - International Center For Tropical Agriculture (CIAT)
item Smith, Douglas
item Schneider, Sharon
item Wente, Christopher - Chris

Submitted to: International Drainage Symposium
Publication Type: Proceedings
Publication Acceptance Date: 4/18/2016
Publication Date: 9/7/2016
Citation: Feyereisen, G.W., Francesconi, W., Smith, D.R., Papiernik, S.K., Wente, C.D. 2016. Open inlet conversion: Water quality benefits of two designs. In: Strock, Jeffrey S. editor. Proceedings of the Tenth International Drainage Symposium. September 7-9, 2016, Minneapolis, Minnesota.

Interpretive Summary:

Technical Abstract: Open surface inlets that connect to subsurface tile drainage systems provide a direct pathway for movement of sediment, nutrients, and agrochemicals to surface waters. This study was conducted to determine the reduction in drainage effluent total suspended sediment (TSS) and phosphorus (P) concentrations and loads when open surface inlets were replaced with blind (in gravel capped with 30 cm of soil) or gravel (in very coarse sand/fine gravel) inlets. In Indiana, a pair of closed depressions in adjacent fields was fitted with open inlet tile risers and blind inlets in 2005 and monitored for flow and water chemistry. Paired comparisons on a storm event basis during the growing season for years 2006 to 2013 showed that TSS loads were 40.4 and 14.4 kg ha-1 event-1 for tile risers and blind inlets, respectively. Total P (TP) and soluble reactive P (SRP) loads were 66 and 50% less for the blind inlets, respectively. In Minnesota, TSS and SRP concentrations were monitored for 3 yr before and after modification of 24 open inlets to gravel inlets in an unreplicated large-field on-farm study. Median TSS concentrations were 97 and 8.3 mg L-1 and median SRP concentrations were 0.099 and 0.064 mg L-1 for the open inlet and gravel inlet periods, respectively. Median TSS and SRP concentrations were elevated for snowmelt vs. non-snowmelt seasons for open and gravel inlets. Both replacement designs reduced suspended sediment and P concentrations and loads. The Indiana study suggests blind inlets will be effective beyond a 10-yr service life.