Formation of a Groundwater Table by Trench Irrigation and Evapotranspiration in a Drained Peatland (Soil Physics)

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To evaluate the coexistence of agricultural managements and wetland ecosystem conservation, the Bibai mire, an ombrotrophic mire in Hokkaido, Japan, was selected as an experimental site that had been affected by neighboring agricultural managements. Since the lowering of the level of the groundwater table in the peripheral area of the mire had threatened indigenous vegetations, keeping the groundwater table shallow by trench irrigation seemed to be an effective measure to recover the original vegetation. The objective of the present study was to quantify the amount of water and the effective area of trench irrigation required in a bamboo-invading area in a pristine mire. We constructed a trench 28m long and irrigated at the rate of 2.22m^3 d^<-1> in a bamboo-invading area in the mire. And to analyze the hydro-meteorological conditions under the trench irrigation, we measured the saturated hydraulic conductivity of the peat layer (3.8×10^<-3>cm s^<-1>), the evapotranspiration rate (2.80mm d^<-1>), the depth of the non-irrigated groundwater table (0.15m) and the surface gradient (0.00493). In addition, using the mass conservation equation and Darcy's law, we derived a steady state model of the level of the groundwater table formed by trench irrigation, which required the five parameters mentioned above. The irrigated water spread over a distance of only about 15m to both sides of the trench. The model also estimated that the distance for the irrigated area was 14.6m and we concluded that the irrigated area was limited within a distance of 20m distances to both sides of the trench and that the irrigation rate per unit trench length did not exceed 0.12m^2 d^<-1> for realistic values of the evapotranspiration rate and the saturated hydraulic conductivity in peatland.
社団法人日本土壌肥料学会の論文

Formation of a Groundwater Table by Trench Irrigation and Evapotranspiration in a Drained Peatland (Soil Physics)

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