Regional streamflow trend detection with consideration of both temporal and spatial correlation

Yue, Sheng; Wang, Chun Y.

doi:10.1002/joc.781

Cited by 171 publications

(138 citation statements)

References 28 publications

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“…However, often the hydro-meteorological time series contain a serial correlation [73][74][75], affecting the MK test results. For instance, existence of a positive (negative) serial correlation in a time series overestimates (underestimates) the significance of the MK test (e.g., [74,76]).…”

Section: Trend-free Pre-whiteningmentioning

confidence: 99%

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Rising Precipitation Extremes across Nepal

Karki

Hasson

Schickhoff

et al. 2017

Climate

208

140

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Abstract:As a mountainous country, Nepal is most susceptible to precipitation extremes and related hazards, including severe floods, landslides and droughts that cause huge losses of life and property, impact the Himalayan environment, and hinder the socioeconomic development of the country. Given that the countrywide assessment of such extremes is still lacking, we present a comprehensive picture of prevailing precipitation extremes observed across Nepal. First, we present the spatial distribution of daily extreme precipitation indices as defined by the Expert Team on Climate Change Detection, Monitoring and Indices (ETCCDMI) from 210 stations over the period of . Then, we analyze the temporal changes in the computed extremes from 76 stations, featuring long-term continuous records for the period of 1970-2012, by applying a non-parametric Mann−Kendall test to identify the existence of a trend and Sen's slope method to calculate the true magnitude of this trend. Further, the local trends in precipitation extremes have been tested for their field significance over the distinct physio-geographical regions of Nepal, such as the lowlands, middle mountains and hills and high mountains in the west (WL, WM and WH, respectively), and likewise, in central (CL, CM and CH) and eastern (EL, EM and EH) Nepal. Our results suggest that the spatial patterns of high-intensity precipitation extremes are quite different to that of annual or monsoonal precipitation. Lowlands (Terai and Siwaliks) that feature relatively low precipitation and less wet days (rainy days) are exposed to high-intensity precipitation extremes. Our trend analysis suggests that the pre-monsoonal precipitation is significantly increasing over the lowlands and CH, while monsoonal precipitation is increasing in WM and CH and decreasing in CM, CL and EL. On the other hand, post-monsoonal precipitation is significantly decreasing across all of Nepal while winter precipitation is decreasing only over the WM region. Both high-intensity precipitation extremes and annual precipitation trends feature east−west contrast, suggesting significant increase over the WM and CH region but decrease over the EM and CM regions. Further, a significant positive trend in the number of consecutive dry days but significant negative trend in the number of wet (rainy) days are observed over the whole of Nepal, implying the prolongation of the dry spell across the country. Overall, the intensification of different precipitation indices over distinct parts of the country indicates region-specific risks of floods, landslides and droughts. The presented findings, in combination with population and environmental pressures, can support in devising the adequate region-specific adaptation strategies for different sectors and in improving the livelihood of the rural communities in Nepal.

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Section: Trend-free Pre-whiteningmentioning

confidence: 99%

“…Various methods are available for assessing the field significance of local trends [71,73,74,[83][84][85][86]. We have adopted the method of Yue et al [74] to assess the field significance in the seven sub-regions (Figure 1b) with sufficient data.…”

Section: Field Significancementioning

confidence: 99%

Rising Precipitation Extremes across Nepal

Karki

Hasson

Schickhoff

et al. 2017

Climate

208

140

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“…These include work in the US (Lins and Slack, 1999;Douglas et al, 2000), Scandinavia (Lindstrom and Bergstrom, 2004), Canada (Zhang et al, 2001;Burn and Hag Elnur, 2002;Yue and Wang, 2002) and more recently, a global assessment by Svensson et al (2005). These studies present evidence of significant variability, but there are many inherent obstacles to attributing observed trends to climate change.…”

Section: Introductionmentioning

confidence: 99%

“…For this reason, trend studies in the US (Lins andSlack, 1999, Douglas et al, 2000) and Canada (Adamowski and Bocci, 2001;Zhang et al, 2001;Burn and Hag Elnur, 2002;Yue and Wang, 2002) have capitalised on networks of undisturbed, natural catchments, such as the representative hydrometric basin network (RHBN) of Canada. The scope for such an approach in much of Europe is limited and in the UK, the task of identifying and interpreting trends in river flow regimes is particularly challenging because of the high degree of heterogeneity in catchment geology, land use and climate -and the pervasive impact of anthropogenic disturbances on flow regimes.…”

Section: Introductionmentioning

confidence: 99%

An assessment of trends in UK runoff and low flows using a network of undisturbed catchments

2006

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In many parts of the world attempts to discern climatic-driven changes in river flow patterns are hindered by the combined impact of other, more direct anthropogenic disturbances such as abstraction and impoundments. This study capitalises on a newly defined 'benchmark' network of natural catchments in the UK to discern natural variability in flow regimes. Trend tests were applied to time series of runoff and indicators of low-flow magnitude and duration for two study periods to assess the sensitivity of trends to the frame of reference over which tests were conducted. Notwithstanding the volatility of the recent past, the results demonstrate a general stability in runoff and low flows since the early 1960s. The strongest signal to emerge from the study is a positive runoff trend for catchments in Scotland, which was resilient to the effect of the study periods. There was also some indication of increasing runoff in maritime western areas of England and Wales. These increases in maritime areas are likely to reflect the dominance of westerly airflows in the recent past, associated with an increase in the North Atlantic Oscillation (NAO) Index. For low flows, there were no compelling trends -significant positive trends over the 1973-2002 period are influenced by a sequence of notably dry years at the start of the period and were not observed over a 40-year time-frame. There are some indications of a tendency towards decreasing low flows in some eastern catchments, but this is supported by few significant results. The results of this study provide a baseline against which to assess longer-term change from historical flow time series and to monitor future change in the benchmark network.

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“…However, most POPs in the Arctic have shown decreasing trends since the early 1990s (refs 6,12,13). A non-parametric Mann-Kendall statistical test 15,16 reveals statistically significant declining trends at a 95% confidence level for ten POPs in weekly measured air concentrations recorded at the Zeppelin Station (1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009) (Supplementary Methods and Table S1). Similar declining trends were also reported at the Alert Station for HCHs and chlordanes 6 .…”

mentioning

confidence: 99%