Sponges or wicks? What is the role of bogs in hydrological response on the Bogong High Plains?

摘要

In 2005, the Victorian government cancelled all licences to graze cattle in alpine areas of the state. One of the goals of this change is to allow the bogs and fens of the high country (above 1000m) to recover from grazing damage; however, there is concern that this recovery could have implications for catchment hydrology. Since the 1950s, alpine bogs have had a reputation as 'sponges' that store water and release it. as base flow. In this paper we summarise analyses of hydrological data from the Bogong High Plains that aimed to further understand the role of bogs in the hydrology of the High Plains and to assess the hydrological sensitivity to changes in the extent or condition of bogs. The hydrology of Bogong High Plains reflects a wet environment with high runoff coefficients and evapotranspiration rates. Snow plays a critical role in storing winter precipitation and contributing to the seasonal runoff peak in late spring. Stream flow is sustained through the summer months by strong baseflows. Groundwater flows are critical to sustaining stream flow during summer and the baseflow volume indicates that the majority of baseflow must originate from hillslope groundwater systems rather than from water stored in the peat bogs of these catchments. The analyses undertaken address potential impacts of changing peatland area or condition on catchment hydrology. The results indicate that the catchment hydrology is likely to have a low sensitivity to changes in peatland area or condition in small catchments. As catchment size increases when streams leave the high plains, the sensitivity further reduces due to the reducing areal proportion of peat in the larger catchments.