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Effect of Replacing Surface Inlets with Blind or Gravel Inlets on Sediment and Phosphorus Subsurface Drainage Losses
Author(s) -
Feyereisen Gary W.,
Francesconi Wendy,
Smith Douglas R.,
Papiernik Sharon K.,
Krueger Erik S.,
Wente Christopher D.
Publication year - 2015
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2014.05.0219
Subject(s) - inlet , tile drainage , hydrology (agriculture) , sediment , snowmelt , environmental science , total suspended solids , effluent , suspended solids , drainage , geology , environmental engineering , soil science , geotechnical engineering , geomorphology , soil water , sewage treatment , chemical oxygen demand , wastewater , snow , ecology , biology
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.