Paul H. Whitfield

Downscaling recent streamflow conditions in British Columbia, Canada using ensemble neural network models

Abstract Variations in climate conditions during recent decades in British Columbia, Canada have occurred coincident to significant changes in streamflow conditions in the province. In the current study, the ability of empirical downscaling models to resolve these changes is investigated using ensemble neural networks forced with synoptic-scale atmospheric conditions. Five-day averages of streamflow data from 21 watersheds in the region are modelled using atmospheric data from the NCEP/NCAR reanalysis project as inputs. Ability of the downscaling models to predict streamflow and changes in streamflow between 1975–1986 and 1987–1998 is evaluated using a combination of model performance statistics, comparisons between long-term averages, and results from non-parametric statistical tests. While performance varied between systems, results suggest that empirical downscaling models for streamflow are capable of predicting changes in streamflow observed during recent decades using only large-scale atmospheric conditions as model inputs. Based on comparisons between stepwise linear regression and neural network models, the latter approach is recommended, particularly when trying to model systems with complex non-linear and interactive relationships between inputs and outputs. The use of ensemble averaging as a part of the modelling process is investigated and a number of recommendations are made with respect to this methodology.

Recent Variations in Climate and Hydrology in Canada

Climatic and hydrologic variations between the decades 1976–1985 and 1986–95 are examined at 210 climate stations for temperature, 271 climate stations for precipitation, and 642 hydrology stations from across Canada. The variations in climate are distributed across a broad spatial area. Temperatures were generally warmer in the more recent decade, with many stations showing significant increases during spring and fall. Significant decreases in temperature were found during winter in eastern Canada. Significant increases in temperature were more frequent in western Canada than in the east. Significant decreases in precipitation were also more prevalent in the north, as were increases in the south, except for Ontario and Quebec where little or no change has taken place. The hydrologic responses to these variations in climate are classified into four hydrograph types and six patterns of shifts in streamfiow between the two decades. The 642 hydrologic stations fall into 16 of the potential 24 groups. These 16 classes demonstrate a strong correspondence to the distribution of ecozones in Canada. In addition, these recent variations illustrate the leverage effect of small variations in climate, particularly temperature, on different hydrologic systems.

Pacific Decadal Oscillation and the Hydroclimatology of Western Canada—Review and Prospects

The Pacific Decadal Oscillation (PDO) is a large-scale climate system feature that influences the surface climate and hydrology of western North America. In this paper, we review the literature describing the PDO and demonstrate its effects on temperature, precipitation, snowfall, glacier mass balance, and streamflow with a focus on western Canada, and particularly British Columbia. We review how the PDO index was developed and discuss other North Pacific climate patterns that resemble the PDO. The impacts of PDO on glacier mass balance and streamflow from retrospective studies are also reviewed and illustrated with specific examples from BC. We assess the current state of knowledge regarding the PDO and provide a critical assessment of its use in hydroclimatology. This information should provide insight on the sensitivity of projects to climatic variability.

Linked Hydrologic and Climate Variations in British Columbia and Yukon

Climatic and hydrologic variations between the decades 1976–1985 and 1986–1995 are examined at 34 climate stations and 275 hydrology stations. The variations in climate are distributedacross a broad spatial area. Temperatures were generally warmerin the most recent decade, with many stations showing significantincreases during the spring and fall. No significant decreases intemperature were found. Significant increases in temperature weremore frequent in the south than in the northern portions of theregion. Significant changes in precipitation were also more prevalent in the south. In coastal areas, there were significantdecreases in precipitation during the dry season, and significantincreases during the wet season. In the BC interior, significantprecipitation decreases occurred during the fall, with significant increases during the winter and spring. In the norththere were few changes in precipitation. The hydrologic responsesto these variations in climate follow six distinctive patterns.The spatial distribution of these patterns suggests that indifferent ecozones, small variations in climate, particularlytemperature, elicit different hydrologic responses.

Some particulate and soluble agents affecting the relationship between metal toxicity and organism survival in the calanoid copepod Euchaeta japonica

Particulate and water-soluble agents were tested to determine their ability to affect the relationship between metal toxicity and the survival of Euchaeta japonica (Copepoda, Calanoida). Clay minerals and diatoms were two types of particles capable of affecting this relationship. Ascorbic acid, sewage effluent, and water extracts of humic acid and two types of soils exhibited the same capability. The ability of the water-soluble agents was compared with that of a known chelating agent in an attempt to quantify the activity of the agents.

Synoptic Map-Pattern Classification Using Recursive Partitioning and Principal Component Analysis

Abstract A method for classifying synoptic-scale maps into discrete groups is introduced. Tree-based recursive partitioning models are used to develop mappings between synoptic-scale circulation fields and the leading linear and nonlinear principal components (PCs) of weather elements observed at a surface station. Statistically unique but climatically insignificant patterns are avoided by identifying map patterns based on their association with indices related to local weather conditions. The method requires few user-adjustable parameters and includes an algorithm that provides objective guidance for determining the appropriate number of map patterns to retain. The classification method is demonstrated using daily sea level pressure and 500-hPa geopotential height maps from a domain covering British Columbia and the northeastern Pacific Ocean. The linear and nonlinear weather element PCs are derived from daily measurements of surface temperature, dewpoint temperature, cloud opacity, and u and υ wind comp...

Spatiotemporal mapping of ENSO and PDO surface meteorological signals in British Columbia, Yukon, and southeast Alaska

Abstract We assessed the impacts of some key Pacific ocean‐atmosphere circulation patterns on annual cycles of temperature and precipitation across British Columbia, Yukon, and southeast Alaska. The El Niño‐Southern Oscillation (ENSO), the Pacific Decadal Oscillation (PDO), and ENSO conditional on PDO states were considered in composite analyses of 71 long, high‐quality datasets from surface meteorological stations. Month‐by‐month, station‐by‐station Monte Carlo bootstrap tests were employed to assess statistical significance. The results trace precipitation and temperature responses as a function of location, season, and climate mode. In summary, temperature responses were relatively uniform, with higher (lower) temperatures during the warm (cool) phases of these circulation patterns. Nevertheless, strength and seasonal persistence varied considerably with location and climate mode. Impacts were generally most consistent in winter and spring but could extend through most of the year. Overall spatiotemporal patterns in precipitation response were decoupled from those in temperature and were far more heterogeneous. Complexities in precipitation signals included north‐south inverse teleconnectivity along the Pacific coast, with a zero‐response hinge point in the approximate vicinity of northern Vancouver Island; seasonally opposite anomalies in several interior regions, which might conceivably reflect contrasting effects of Pacific climate modes on wintertime frontal storms versus summertime convective storms; and a consistent lack of substantial response in northwestern British Columbia and possibly southwestern Yukon, conjectured to reflect complications associated with the Icefield Ranges. The product is intended primarily as a basic‐level set of climate response maps for hydrologists, biologists, foresters, and others who require empirical assessments of relatively local‐scale, year‐round ENSO and PDO effects across this broad region.

Modelling Streamflow in Present and Future Climates: Examples from the Georgia Basin, British Columbia

The Georgia Basin is one of the most hydrologically complex areas of Canada. The form in which precipitation occurs in winter, either snow or rain, is the primary determinant of the hydrologic patterns of rivers. The region consists of mountains, valleys and plains, and has extensive variations in elevation. Variations in temperature and precipitation exert tremendous influence on the amount and form of water that reaches the land surface of the Georgia Basin. The amalgamation of the climatic and geographical factors creates homogenous zones in which distinctly different hydrological processes occur. Climate change could have major regional effects on temperature, precipitation, evapotranspiration and ultimately runoff. In previous work, zones of homogenous hydrologic processes in the Georgia Basin were delineated. In the present work, we used downscaled data from GCMs for future periods as inputs to a hydrologic model. These results are used to forecast the location of these zones in three periods in the 21st century. The results indicate important changes to the three hydrologic types found in the Georgia Basin: rainfall-driven streams demonstrate increased winter flows, snowmelt-driven streams demonstrate an increasingly early onset to spring snowmelt, and hybrid (mixed rain and snow) streams become increasingly rainfall driven. These large changes illustrate some of the impacts to which the Pacific Northwest may have to adapt in the near future.

Seasonal and long-term variations in water quality of the Skeena River at Usk, British Columbia

This study analysed data collected from the Skeena River at Usk every 2 weeks between 1984 and 1992 to determine the processes affecting the water quality. In addition, this study assessed the data for the presence of trends (changes in the overall mean of the time-series), modelled the series and forecast future water quality of the river. Hysteresis diagrams were used to determine which processes affect water quality. These diagrams revealed the importance of snowmelt and rainfall peaks on water chemistry. Plots of the water quality variables against time indicated no trends during the study period. Univariate Box-Jenkins techniques were used to model the observed patterns in water quality. These models were then used to project past patterns and relationships into the future (forecasting). These anticipated forecasts may then aid in planning and decision making. The sign test was used to confirm that no trends were present during the study period.

Reference hydrologic networks I. The status and potential future directions of national reference hydrologic networks for detecting trends

Abstract Identifying climate-driven trends in river flows on a global basis is hampered by a lack of long, quality time series data for rivers with relatively undisturbed regimes. This is a global problem compounded by the lack of support for essential long-term monitoring. Experience demonstrates that, with clear strategic objectives, and the support of sponsoring organizations, reference hydrologic networks can constitute an exceptionally valuable data source to effectively identify, quantify and interpret hydrological change—the speed and magnitude of which is expected to a be a primary driver of water management and flood alleviation strategies through the future—and for additional applications. Reference hydrologic networks have been developed in many countries in the past few decades. These collections of streamflow gauging stations, that are maintained and operated with the intention of observing how the hydrology of watersheds responds to variations in climate, are described. The status of networks under development is summarized. We suggest a plan of actions to make more effective use of this collection of networks. Editor Z.W. Kundzewicz; Associate editor K. Hamed Citation Whitfield, P.H., et al., 2012. Reference hydrologic networks I. The status and potential future directions of national reference hydrologic networks for detecting trends. Hydrological Sciences Journal, 57 (8), 1562–1579.