EGU2020-13704, updated on 12 Jun 2020
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Maintenance of high peatland water levels by subsurface water regulation

Merten Minke, Ann Christin Sieber, Arne Tegge, and Heinrich Höper
Merten Minke et al.
  • State Authority for Mining, Energy and Geology Lower Saxony, Hannover, Germany (

About 30% (0.4 Mha) of German peatlands are located in Lower Saxony and about 65% of these peatlands are used for agriculture, mainly grassland. These peatlands are drained for agricultural use, which creates huge GHG emissions. Grasslands on carbon rich soils are responsible for seven percent of the GHG budget of Lower Saxony. Raising the annual water level to 30 cm below surface or higher should substantially reduce peat oxidation and GHG emissions from such sites, while allowing grassland management or other ways of peatland utilization under wet conditions. Such water levels, however, may be difficult to achieve by high ditch water levels alone, because the low hydraulic conductivity of the degraded peat does not allow sufficient water movement to compensate for evapotranspiration in summer. We hypothesize that subsurface water regulation may allow constant high peatland water levels, because the applied submerged drains form conduits from ditches into the peat that should improve the water exchange.

We tested subsurface water regulation at 1 ha plots on a fen and bog grassland in NW-Germany. Both sites included three treatments: (1) blocked ditches with subsurface water regulation, (2) blocked ditches without subsurface water regulation, and (3) conventional drainage (control). Ditches in treatments (1) and (2) were filled with surface water up to 15 cm below land surface during the growing season using a solar pump. Over a period of three years, we monitored ditch and peatland water levels along transects. We analyzed effects of treatments, ditch water levels, climatic water balance, and saturated water conductivity (kf) on peatland water levels and changes of surface elevation.

Our results show that subsurface water regulation allowed for a better control of peatland water levels as compared to ditch blocking and conventional drainage. In the winter, subsurface water regulation improved drainage, so that water levels within the site were not much higher than the ditch water levels. In the summer, subsurface water regulation allowed to maintain peatland water levels of 30 to 40 cm below surface, more than 20 cm higher compared to both other treatments. Furthermore, subsurface water regulation reduced subsidence. However, despite a narrow drain spacing of four to five meters, it was difficult to maintain the target peatland water levels during very dry summer months albeit the tested years were atypically dry and hot. The differences between ditch water levels and peatland water levels were closely related to the climatic water balance, and the slope of the linear function depended on saturated water conductivity (kf) of the peat. Based on climatic water balances, weir adjustment can be optimized to achieve high and stable peatland water levels. The results help in understanding and analyzing the hydrology of degraded peatlands. This information will prove extremely useful for planning water management measures, which are necessary to reduce the GHG emissions from drained peatlands.

How to cite: Minke, M., Sieber, A. C., Tegge, A., and Höper, H.: Maintenance of high peatland water levels by subsurface water regulation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13704,, 2020


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displays version 1 – uploaded on 05 May 2020
  • CC1: Comment on EGU2020-13704, Ko van Huissteden, 07 May 2020

    Hi Merten, nice experiment. I am involved in peat conservation efforts in the Netherlands, also using subsurface drainage and ditch blocking. I see a very large difference in the effectiveness of ditch blocking between the two sites. Could this be related to the peat characteristics?

    • AC1: Reply to CC1, Merten Minke, 07 May 2020

      Dear Ko,

      the main reason for the difference seems to be the kf (water saturated hydraulic conductivity). The peat of the fen is more dense, and kf below 10 cm / day. That of the bog is more loose and kf above 10 cm / day. When analysing the summer water table in relation to the distance to the ditch, we found that at the bog the water taable at 10 m distance was only about 20 cm below the ditch, but at the fen the difference is about 50 cm.


      • CC2: Reply to AC1, Ko van Huissteden, 07 May 2020

        Hi Merten, thanks!

        • AC2: Reply to CC2, Merten Minke, 07 May 2020

          Dear Ko,

          I was glad to receive your question and to read that you also work with ditch blocking and subsurface water regulation. Let us exchange experiences on this.

          Best wishes


  • CC3: Comment on EGU2020-13704, Ko van Huissteden, 07 May 2020

    Sure, my e-mail is still; I will forward you also to Jim Boonman who also presented today