Hydrologic characterization and restoration of a mountain fen-complex, Drakesbad Meadow, Lassen Volcanic National Park, Cascade Range, California

Patterson, Lindsay

Two pilot projects were undertaken to restore these hydrologic modifications; the historic off-site hydrologic regime was re-established by digging channels across the road at areas identified as spring discharge points. Installation of cross channels that re-connected the major flowpaths from the spring complex to the wetland caused dramatic changes in depth of the water table at many well sites. Areas closest to the road re-wetted first and in many wells the water table rose from greater than 70 cm to less than 10 cm below the soil surface. To reverse the effects of one main drainage ditch, five sheet metal dams were installed perpendicular to the direction of flow. Installation of the dams resulted in a rapid rise in the water table downslope of the dams. Similar to the response of areas impacted by the road, areas impacted by the drainage ditch showed a rise in water table from greater than 60 cm below the soil surface to less than 10 cm. Restoration activities increased the correlation between organic soil depth and late July water table depth, suggesting that the hydrologic regime was successfully restored. One year following restoration, the percent canopy cover of peat forming species Carex simulata, Carex utriculata and Scirpus microcarpus increased, while the percent cover of the grass species Deschampsia cespitosa, Hordeum brachyantherum and Poa pratensis decreased. To complete restoration of the Drakesbad Meadow fen-complex and re-establish peat accumulating process, drainage ditches, including areas not addressed during this study, should be filled in with soil and allowed to re-vegetate. Likewise, the impacts of the water tank road must be limited or eliminated. This can be accomplished through appropriately installed and maintained culverts, or by eliminating the road and re-grading the hillslope. Active restoration efforts such as these are necessary to prevent further degradation of the Drakesbad Meadow fen-complex, since fens of this region are extremely sensitive to, and unable to persist under, drought-like conditions created by hydrologic modifications.

Hydrologic characterization and restoration of a mountain fen-complex, Drakesbad Meadow, Lassen Volcanic National Park, Cascade Range, California

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