Corrected prediction intervals for change detection in paired watershed studies

Som, Nicholas A.; Zégre, Nicolas; Ganio, Lisa M.; Skaugset, Arne E.

doi:10.1080/02626667.2011.637494

Cited by 10 publications

(13 citation statements)

References 25 publications

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“…To assist in assessing the significance of the treatment effects, 95% prediction intervals were computed. While 1242 S. M. GUENTHER, T. GOMI AND R. D. MOORE Som et al (2012) derived an algebraic expression for computing prediction limits in the presence of autocorrelated error terms, we generated them using Monte Carlo simulation (Leach et al, 2012). To account for uncertainty in the estimates of the parameters r 1 , b 0 , etc., separate parameter sets were generated for each of 1000 realizations using the estimated variance-covariance matrix for the parameter estimates in the rmvnorm() function in the R programming language (R Development Core Team, 2011), which generates multivariate normal random numbers.…”

Section: Paired-catchment Analysismentioning

confidence: 99%

Stream and bed temperature variability in a coastal headwater catchment: influences of surface-subsurface interactions and partial-retention forest harvesting

Guenther¹,

Gomi

Moore

2012

Hydrol. Process.

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Stream temperature was recorded between 2002 and 2005 at four sites in a coastal headwater catchment in British Columbia, Canada. Shallow groundwater temperatures, along with bed temperature profiles at depths of 1 to 30 cm, were recorded at 10‐min intervals in two hydrologically distinct reaches beginning in 2003 or 2004, depending on the site. The lower reach had smaller discharge contributions via lateral inflow from the hillslopes and fewer areas with upwelling (UW) and/or neutral flow across the stream bed compared to the middle reach. Bed temperatures were greater than those of shallow groundwater during summer, with higher temperatures in areas of downwelling (DW) flow compared to areas of neutral and UW flow. A paired‐catchment analysis revealed that partial‐retention forest harvesting in autumn 2004 resulted in higher daily maximum stream and bed temperatures but smaller changes in daily minima. Changes in daily maximum stream temperature, averaged over July and August of the post‐harvest year, ranged from 1.6 to 3 °C at different locations within the cut block. Post‐harvest changes in bed temperature in the lower reach were smaller than the changes in stream temperature, greater at sites with DW flow, and decreased with depth at both UW and DW sites, dropping to about 1 °C at a depth of 30 cm. In the middle reach, changes in daily maximum bed temperature, averaged over July and August, were generally about 1 °C and did not vary significantly with depth. The pre‐harvest regression models for shallow groundwater were not suitable for applying the paired‐catchment analysis to estimate the effects of harvesting. However, shallow groundwater was warmer at the lower reach following harvesting, despite generally cooler weather compared to the pre‐harvest year. Copyright © 2012 John Wiley & Sons, Ltd.

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Section: Paired-catchment Analysismentioning

confidence: 99%

Stream and bed temperature variability in a coastal headwater catchment: influences of surface-subsurface interactions and partial-retention forest harvesting

Guenther¹,

Gomi

Moore

2012

Hydrol. Process.

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“…Som et al. [34] demonstrate that use of classical ordinary least squares (OLS) approach to detect statistically significant treatment effects may not account for temporal autocorrelation of hydrologic data and thus may give incorrect prediction confidence intervals. Work by [35] highlights the limitation of the approach to quantifying effects of urbanization on components of the hydrologic cycle.…”

Section: Introductionmentioning

confidence: 99%

Consistency of Hydrologic Relationships of a Paired Watershed Approach

Ssegane¹,

Amatya²,

Chescheir³

et al. 2013

AJCC

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Paired watershed studies are used around the world to evaluate and quantify effects of forest and water management practices on hydrology and water quality. The basic concept uses two neighboring watersheds (one as a control and another as a treatment), which are concurrently monitored during calibration (pre-treatment) and post-treatment periods. A statistically significant relationship between the control and treatment watersheds is established during calibration period such that any significant shift detected in the relationship during treatment is attributed to the treatment effects. The approach assumes that there is a consistent, quantifiable, and predictable relationship between watershed response variables. This study tests the hypothesis that the hydrologic relationships between control and treatment watersheds for daily water table elevation (WTE) and daily flow data were similar without any statistically significant difference during two different calibration (1988-1989 and 2007-2008) and treatment periods (1995-1996 and 2009), when the control and treatment watersheds were interchanged. The watersheds are two artificially drained loblolly pine forests (D1: 24.7 ha and D2: 23.6 ha) located in coastal North Carolina. Results depicted significantly similar WTE regression relationships during the two calibration periods but significantly different WTE relationships during the two treatment periods with reversed control and treatment watersheds. Calibration and treatment flow relationships, and the mean treatment effects on WTE and flow, before and after treatment reversal were significantly different (α = 0.05). The study also discusses causes of differences in hydrologic relationships and treatment effects for such reversal of treatments during a 21-year span of the study on these two similar and adjacent watersheds. The observed differences in the hydrologic relationships between control and treatment watersheds before and after treatment reversal may be attributed to climate or hydrologic non-stationarity which may affect the reliability of paired watershed approach especially when the calibration periods are short.

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“…Since these random disturbances are independent, 95% confidence limits could be estimated as ± 1.96 σ ( M r ). As suggested by Watson et al () and Som et al (), if more than 5% of the values of M r exceeded the 95% confidence limits, a statistically significant manipulation of a hydrometeorological characteristic of the lake was implied. When the data of any parameter did not adhere to the assumptions of this method, analysis of variance (ANOVA) and a paired t ‐test were used to evaluate if there was a difference in observations and predicted post‐manipulation values.…”

Section: Methodsmentioning

confidence: 81%

“…A common approach in paired catchment studies (Watson et al ; Moore et al 2005; Gomi et al 2006; Som et al ) to detecting change due to a manipulation includes three steps. The first step is to derive a relationship between the entire dataset of control and pre‐manipulation responses, which in this study could be of the form:

{x'}_{626, t} = m_{x} \cdot x_{373, t} + b_{x} + ε_{x}

where x ′ 626, t is a predicted value of x 626, t using x 373, t where x is a hydrometeorological characteristic of the lake (i.e., DOC concentration, light extinction, surface temperature, evaporation rate) on day t .…”

Section: Methodsmentioning

confidence: 99%

“…The non-linear relationship between precipitation and connectivity in boreal regions is primarily due to heterogeneity in land cover and topography (Devito et al 2005;Buffam et al 2007;Laudon et al 2012). This heterogeneity creates a threshold-mediated streamflow generation process (Allan and Roulet 1994;Peters et al 1995;Spence and Woo 2003) that results in a dichotomy of either connection or non-connection depending on antecedent conditions and water inputs. This characteristic of streamflow generation in the boreal region is important because it controls the nature of biogeochemical connectivity and transfer of material from catchments into lakes (Allan et al 1993).…”

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confidence: 99%

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The impact of a loss of hydrologic connectivity on boreal lake thermal and evaporative regimes

Spence

Beaty

Blanchfield

et al. 2018

Limnology & Oceanography

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This paper summarizes the initial results (first 4 yr) of a whole‐catchment manipulation to evaluate the impact of a loss of hydrologic connectivity of a boreal lake with its watershed on lake thermal and evaporative regimes. We diverted the upstream flow to a fourth order lake resulting in a marked reduction (81%) in watershed area, and compared the response to a comparable control lake in a headwater position. The manipulation reduced runoff into the experimental lake from 2400 mm to 90 mm, greatly increased theoretical residence time (from 2.3 yr to 18.3 yr), and reduced average dissolved organic carbon concentration from 5.8 ± 0.3 mg L−1 to 5.5 ± 0.3 mg L−1. Average Secchi depth was increased by 0.6 m, resulting in a 0.25 m deeper epilimnion and cooler surface water temperatures (8% of the time) than those predicted by pre‐manipulation relationships. There was some evidence that the response of evaporation to episodic events was altered, but this was not extensive enough to alter annual evaporation or median evaporation rates. Our findings show that the impacts of hydrologic connectivity on lake chemistry can cascade to alter the energy budgets of boreal lakes. These results can inform how differences in hydrological connectivity across the landscape due to lake‐watershed topology and climate will impact boreal lakes. Of note is that very clear lakes in the boreal region are highly sensitive to impacts from a change in clarity. Information on their spatial distribution will be necessary to assess impacts of hydrological connectivity on the boreal lake complex.

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Corrected prediction intervals for change detection in paired watershed studies

Cited by 10 publications

References 25 publications

Stream and bed temperature variability in a coastal headwater catchment: influences of surface-subsurface interactions and partial-retention forest harvesting

Stream and bed temperature variability in a coastal headwater catchment: influences of surface-subsurface interactions and partial-retention forest harvesting

Consistency of Hydrologic Relationships of a Paired Watershed Approach

The impact of a loss of hydrologic connectivity on boreal lake thermal and evaporative regimes

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