Evaluation of methods for estimating the effects of vegetation change and climate variability on streamflow

Abstract

[1] Changes in vegetation cover can significantly affect streamflow. Two common methods for estimating vegetation effects on streamflow are the paired catchment method and the time trend analysis technique. In this study, the performance of these methods is evaluated using data from paired catchments in Australia, New Zealand, and South Africa. Results show that these methods generally yield consistent estimates of the vegetation effect, and most of the observed streamflow changes are attributable to vegetation change. These estimates are realistic and are supported by the vegetation history. The accuracy of the estimates, however, largely depends on the length of calibration periods or pretreatment periods. For catchments with short or no pretreatment periods, we find that statistically identified prechange periods can be used as calibration periods. Because streamflow also responds to climate variability, in assessing streamflow changes it is necessary to consider the effect of climate in addition to the effect of vegetation. Here, the climate effect on streamflow was estimated using a sensitivity-based method that calculates changes in rainfall and potential evaporation. A unifying conceptual framework, based on the assumption that climate and vegetation are the only drivers for streamflow changes, enables comparison of all three methods. It is shown that these methods provide consistent estimates of vegetation and climate effects on streamflow for the catchments considered. An advantage of the time trend analysis and sensitivity-based methods is that they are applicable to nonpaired catchments, making them potentially useful in large catchments undergoing vegetation change.

Impacts of forest changes on hydrology: a case study of large watersheds in the upper reaches of Minjiang River watershed in China

“…However, such an experimental approach is not suitable for large watersheds simply because of the difficulty in locating a comparable control watershed for an impacted watershed. In order to overcome this methodological challenge, various approaches have been explored, including hydrological modeling (Tuteja et al, 2007), statistical analysis (Wei and Zhang, 2010;Zhao et al, 2010), sensitivity tests (Milly and Dunne, 2002) and trend analysis (Wilcox and Huang, 2010).…”

The effects of cumulative forest disturbance on streamflow in a large watershed in the central interior of British Columbia, Canada

“…The greatest challenge is how to separate their relative contributions to hydrology (Zhang et al, 2008;Wang et al, 2009;Zheng et al, 2009;Wei and Zhang, 2010b). Physically-based hydrological modeling is commonly used to assess the relative effects of climate variability and forest change on hydrology (Tuteja et al, 2007;Juckem et al, 2008;Zégre et al, 2010;Zhao et al, 2010). However, this modeling approach is only suitable for the watersheds that are well monitored with extensive, longterm data available on vegetation, soil, topography, land use, hydrology and climate (Wei and Zhang, 2010a, b).…”

Predicting effects of plantation expansion on streamflow regime for catchments in Australia

“…One of the key components of FCFC is the method of Zhang et al (2001) for estimating differences in mean annual streamflow under different degrees of forest cover. The method of Zhang et al (2001) has been widely used (Jackson et al, 2005;Sun et al, 2006) and a number of studies tested its accuracy using data from experimental catchments (Brown et al, 2005;Zhao et al, 2010). Brown et al (2005) compared estimated changes in mean annual streamflow using the method of Zhang et al (2001) with those observed from paired catchment studies, and showed that the method of Zhang et al (2001) yielded good estimates of the changes in mean annual streamflow from catchments involving conifer and eucalyptus.…”

“…Brown et al (2005) compared estimated changes in mean annual streamflow using the method of Zhang et al (2001) with those observed from paired catchment studies, and showed that the method of Zhang et al (2001) yielded good estimates of the changes in mean annual streamflow from catchments involving conifer and eucalyptus. Zhao et al (2010) evaluated methods for estimating the effects of vegetation cover change on streamflow using paired catchment data from Australia, New Zealand, and South Africa. The study showed that the method of Zhang et al (2001) provided consistent estimates of vegetation impact on mean annual streamflow compared with paired catchment method and time-trend analysis method.…”

“…Our understanding of the vegetation impact on mean annual water yield is well advanced, and there are robust methods available for assessing the impact (Bosch and Hewlett, 1982;Zhang et al, 2001;Brown et al, 2005;Zhao et al, 2010;Wei and Zhang, 2010). Recently, a number of studies focused on changes in flow regime following vegetation cover changes and showed different responses in high flows and low flows (Lane et al, 2005;Brown et al, 2006).…”