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This content will become publicly available on January 19, 2017

Title: High-frequency monitoring of water fluxes and nutrient loads to assess the effects of controlled drainage on water storage and nutrient transport

High nitrogen (N) and phosphorus (P) fluxes from upstream agriculture threaten aquatic ecosystems in surface waters and estuaries, especially in areas characterized by high agricultural N and P inputs and densely drained catchments like the Netherlands. Controlled drainage has been recognized as an effective option to optimize soil moisture conditions for agriculture and to reduce unnecessary losses of fresh water and nutrients. This is achieved by introducing control structures with adjustable overflow levels into subsurface tube drain systems. A small-scale (1 ha) field experiment was designed to investigate the hydrological and chemical changes after introducing controlled drainage. Precipitation rates and the response of water tables and drain fluxes were measured in the periods before the introduction of controlled drainage (2007–2008) and after (2009–2011). For the N and P concentration measurements, auto-analyzers for continuous records were combined with passive samplers for time-averaged concentrations at individual drain outlets. The experimental setup enabled the quantification of changes in the water and solute balance after introducing controlled drainage. The results showed that introducing controlled drainage reduced the drain discharge and increased the groundwater storage in the field. To achieve this, the overflow levels have to be elevated in early spring, before the drain dischargemore » stops due to dryer conditions and falling groundwater levels. The groundwater storage in the field would have been larger if the water levels in the adjacent ditch were controlled as well by an adjustable weir. The N concentrations and loads increased, which was largely related to elevated concentrations in one of the three monitored tube drains. The P loads via the tube drains reduced due to the reduction in discharge after introducing controlled drainage. Furthermore, this may be counteracted by the higher groundwater levels and the larger contribution of N- and P-rich shallow groundwater and overland flow to the surface water.« less
Authors:
 [1] ;  [2] ;  [1] ;  [3] ;  [4] ;  [1] ;  [5]
  1. Deltares, Utrecht (The Netherlands)
  2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  3. Allseas Engineering, Delft (The Netherlands)
  4. VU Univ., Amsterdam (The Netherlands)
  5. TNO Geological Survey of the Netherlands, Utrecht (The Netherlands)
Publication Date:
OSTI Identifier:
1259779
Report Number(s):
LLNL-JRNL--693974
Journal ID: ISSN 1607-7938
Grant/Contract Number:
AC52-07NA27344
Type:
Accepted Manuscript
Journal Name:
Hydrology and Earth System Sciences (Online)
Additional Journal Information:
Journal Name: Hydrology and Earth System Sciences (Online); Journal Volume: 20; Journal Issue: 1; Journal ID: ISSN 1607-7938
Publisher:
European Geosciences Union (EGU)
Research Org:
Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES controlled drainage; water conservation; nutrients; agriculture