Abstract
Abstract. Most of the forested headwater catchments are an important source of water supply in many parts of the world. A prime example is southeast Australia where forests supply major river systems and towns and cities with water. It is critical for an informed and adaptive water resource management to understand changes in streamflow caused by vegetation changes in these headwater forest catchments. Natural disturbances such as bushfires and anthropogenic activities like forestation, deforestation, or logging alter vegetation, evapotranspiration and soil water status, and may affect water supplies. Although catchment water yield is mainly controlled by climatic conditions, but it is also strongly influenced by land cover changes because of natural disturbances and anthropogenic activities. It is necessary to accurately estimate streamflow in water supply catchments subjected to dramatic land surface changes. This paper summarises the methods commonly used to investigate the impacts of land cover change on water resources, and provides some examples of impacts of afforestation/deforestation and bushfire on water resources in two southeast Australian catchments.
Highlights
There are numerous studies reported in literature which investigate the impacts of land use/land cover change and climate variability on catchment water availability (Vertessy, 1999; Vaze et al, 2004; Zhao et al, 2010; Nangia et al, 2010) and there is sufficient evidence that afforestation can reduce streamflow substantially (Zhang et al, 2001; Jackson et al, 2005; Lane et al, 2005)
Most of the forested headwater catchments are an important source of water supply in many parts of the world
It is important for responsible water resource management to understand changes in streamflow caused by vegetation dynamics in these headwater forest catchments
Summary
There are numerous studies reported in literature which investigate the impacts of land use/land cover change and climate variability on catchment water availability (Vertessy, 1999; Vaze et al, 2004; Zhao et al, 2010; Nangia et al, 2010) and there is sufficient evidence that afforestation can reduce streamflow substantially (Zhang et al, 2001; Jackson et al, 2005; Lane et al, 2005). Streamflow increases immediately following the destruction of mature forest due to the reduction in interception and water use. The streamflow decreases as the forest regrows and increases water use. There is normally an increase in streamflow immediately following deforestation/clearing and this increase varies depending on the forest type and climate zone (Fig. 1a). The decrease in streamflow during the regrowth period following deforestation/bushfire is dependent on the forest type and climate zone but the variability is much higher in the case of bushfire as there can be either a “full recovery” or only a “partial recovery” and it is a function of the severity of the disturbance and area burnt (Fig. 1b). In case of a full recovery after bushfire, we expect the streamflow to decrease to be pretty much same as that of the pre-bushfire period but the recovery time is dependent on the forest type and postbushfire climatic conditions
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