Assessing the relations between aquatic habitat indicators and forest harvesting at watershed scale in the interior of British Columbia

2019

Forests

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Climatic variability and cumulative forest cover change are the two dominant factors affecting hydrological variability in forested watersheds. Separating the relative effects of each factor on streamflow is gaining increasing attention. This study adds to the body of literature by quantifying the relative contributions of those two drivers to the changes in annual mean flow, low flow, and high flow in a large forested snow dominated watershed, the Deadman River watershed (878 km2) in the Southern Interior of British Columbia, Canada. Over the study period of 1962 to 2012, the cumulative effects of forest disturbance significantly affected the annual mean streamflow. The effects became statistically significant in 1989 at the cumulative forest disturbance level of 12.4% of the watershed area. The modified double mass curve and sensitivity-based methods consistently revealed that forest disturbance and climate variability both increased annual mean streamflow during the disturbance period (1989–2012), with an average increment of 14 mm and 6 mm, respectively. The paired-year approach was used to further investigate the relative contributions to low and high flows. Our analysis showed that low and high flow increased significantly by 19% and 58%, respectively over the disturbance period (p < 0.05). We conclude that forest disturbance and climate variability have significantly increased annual mean flow, low flow and high flow over the last 50 years in a cumulative and additive manner in the Deadman River watershed.

Section: Management Implicationsmentioning

confidence: 99%

The Cumulative Effects of Forest Disturbance and Climate Variability on Streamflow in the Deadman River Watershed

Giles-Hansen

2019

Forests

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“…Equivalent clear‐cut area (ECA) was used as an indicator to express the forest disturbance level as not only can it represent all types of disturbances and the range of their intensities but it can also include their cumulative forest disturbance histories and subsequent recovery processes that follow disturbances over space and time (Hudson, ; Talbot and Plamondon, ; Winkler et al ., ; Lewis and Huggard, ; Wei and Zhang, ). Although ECA has been successfully used in British Columbia, Canada, to test watershed‐scale forest disturbances and their effects on various watershed processes (Whitaker et al ., ; Chen and Wei, ; Jost et al ., ; Lin and Wei, ), to our knowledge, its utility in representing all types of forest disturbances in a single large watershed for hydrological studies has not been applied. The objectives of this study were (1) to derive a watershed‐scale cumulative forest disturbance indicator accounting for all types of forest disturbances and subsequent regenerations over time; (2) to assess the impact of cumulative forest disturbances on all the components of flow regimes (magnitude, frequency, timing, duration and variability) of high and low flows (see the definitions in the Methods section); and (3) to discuss the potential ecological implications of those flow alterations caused by cumulative forest disturbances.…”

Section: Introductionmentioning

confidence: 99%

Alteration of flow regimes caused by large‐scale forest disturbance: a case study from a large watershed in the interior of British Columbia, Canada

Zhang

2013

Ecohydrology

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Forest disturbance can greatly alter flow regimes and consequently the structures and functions of ecosystems. However, the impacts of forest disturbance on flow regimes have rarely been investigated in large watersheds. In this study, we used a large severely disturbed watershed, the Baker Creek watershed located in the central interior of British Columbia, Canada, to examine how forest disturbance altered the flow regimes and to discuss the possible ecological implications of these alterations. Equivalent clear-cut area, an indicator combining all types of forest disturbances and accounting for hydrological recovery, was adopted to represent the cumulative forest disturbance levels over time at a watershed scale. Flow duration curves and time series cross-correlation analysis were used to detect the statistical significance of relationships between flow regimes (magnitude, duration, timing, frequency and variability of high flows and low flows) and forest disturbance (clear-cut area). The results showed that the magnitude of high flows was significantly increased and the timing of high flows was significantly advanced by forest disturbance. After forest disturbance, the occurrence of high flows with greater return periods became more frequent with increased variations. In addition, forest disturbance significantly increased the magnitude of low flows but with reduced variability. On average, high flows and low flows in the disturbed period were 31Á4% and 16Á0% greater than those in the reference period, respectively. Possible ecological implications of these hydrological alterations caused by forest disturbance were also discussed.

“…Research has established the relationships between vegetation growth (ages or tree heights) following disturbance and hydrological recovery rates, so that ECA can be derived spatially and temporally in a watershed (Hudson, 2000;Talbot and Plamondon, 2002;Winkler et al, 2005;Lewis and Huggard, 2010). The ECA has already been successfully used in British Columbia, Canada, to test watershed-scale forest disturbances and their effects on various watershed processes including aquatic habitat (Chen and Wei, 2008), hydrology (Lin and Wei, 2008) and aquatic biology (Whitaker et al, 2002;Jost et al, 2008). In spite of growing recognition of ECA, its utility in representing various types of forest disturbance (including mountain pine beetle infestation, harvesting, and fire) in a single large watershed for hydrological studies has not been applied as far as we know.…”

mentioning

confidence: 99%

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

Zhang

Hydrol. Earth Syst. Sci.

2012

Abstract. The Baker Creek watershed (1570 km 2 ), situated in the central interior of British Columbia, Canada, has been severely disturbed by both logging and natural disturbance, particularly by a recent large-scale mountain pine beetle (MPB) infestation (up to 2009, 70.2 % of the watershed area had been attacked by MPB) and subsequent salvage logging. The concept of equivalent clear-cut area (ECA) was used to indicate the magnitude of forest disturbance, with consideration of hydrological recovery following various types of disturbance (wildfire, logging and MPB infestation), cumulated over space and time in the watershed. The cumulative ECA peaked at 62.2 % in 2009. A combined approach of statistical analysis (i.e. time series analysis) and graphic method (modified double mass curve) was employed to evaluate the impacts of forest disturbance on hydrology. Our results showed that severe forest disturbance significantly increased annual mean flow. The average increment in annual mean flow caused by forest disturbance was 48.4 mm yr −1 , while the average decrease in annual mean flow caused by climatic variability during the same disturbance period was 35.5 mm yr −1 . The opposite changes in directions and magnitudes clearly suggest an offsetting effect between forest disturbance and climatic variability, with the absolute influential strength of forest disturbance (57.7 %) overriding that from climate variability (42.3 %). Forest disturbance also produced significant positive effects on low flow and dry season (fall and winter) mean flow. Implications of our findings for future forest and water resources management are discussed in the context of long-term watershed sustainability.