The Role of Large-Scale Climate Modes in Regional Streamflow Variability and Implications for Water Supply Forecasting: A Case Study of the Canadian Columbia River Basin

Abstract

The impacts of large-scale modes of climate variability on the annual cycle of terrestrial hydrometeorology in the Canadian Columbia River basin were assessed with the aim of updating our current understanding and identifying opportunities for climate-informed, early-season water supply forecasting. Composite analyses of streamflow from seven Water Survey of Canada gauging stations conditional on El Niño-Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), Pacific/North American pattern (PNA), Arctic Oscillation (AO), and North Pacific Gyre Oscillation (NPGO) states revealed that hydrological impacts of a climate mode could be manifested through changes in the annual runoff volume and/or changes in seasonal runoff patterns. Responses were generally non-linear. Considering ENSO and the PDO, for instance, streamflow anomalies associated with their warm phases contrast with those associated with their cool phases; however, the warm phases tend to produce more consistent streamflow responses than the cool phases. More profoundly, the PNA and AO streamflow responses appear to be highly asymmetrical-only one phase (positive PNA and negative AO) is shown to significantly affect streamflow. Some North Pacific climate indices and ENSO show reasonably consistent and strong correlations with streamflow, which suggests that further refinement of climate-informed early season water supply forecasting is possible. It is shown that further improvement of forecast skills can be attained if North Pacific climate information is included in addition to ENSO in the current generation of operational statistical water supply forecast models.

Seasonal flows of international British Columbia-Alaska rivers: The nonlinear influence of ocean-atmosphere circulation patterns

“…Monotonically nonlinear associations indicate that the water resource responses to the positive and negative phases of a given climate mode are not simple mirror images of each other. These have been widely observed for some ocean-atmosphere circulation patterns, including ENSO and PDO teleconnections in southeast Alaska and northwest BC (e.g., [20,25]). Generally speaking, strongly nonlinear (parabolic) streamflow teleconnections appear substantially less prevalent here than in some other areas of the northern hemisphere (cf.…”

“…Many of the specific hydroclimatic processes inferred, such as higher autumn-winter streamflows or earlier snowmelt freshets under warmer air temperatures, have been widely observed either in this region, or alternatively in other areas of western North America (e.g., [3,22,25,68]). Our inference of higher-thannormal precipitation and streamflow in fall and early winter during ENSO and PDO warm phases is opposite to what is observed for the Pacific Northwest (PNW; [54,58]), to the south of our study area.…”

“…This can be particularly important for international rivers, where institutions for transboundary water management benefit from and may specifically require operational forecasts; various water supply forecasting activities undertaken individually and collectively by both Canadian and US authorities for the transboundary Columbia River provide a nearby example. The most common and arguably still the most effective approach to seasonal-scale water supply forecasting in western North America remains statistical regressions upon various predictor variables, which increasingly include climate indices, such as those for ENSO or PDO (e.g., [25,38,67]). Conventionally, climatewater supply relationships are taken to be linear in such applications.…”

“…For example, climate-based seasonal water supply forecasting can increase yearly hydroelectric http://dx.doi.org/10.1016/j.advwatres.2015. 10.007 0309-1708/Published by Elsevier Ltd. production revenue on the transboundary (Canada-US) Columbia River by hundreds of millions of dollars [27], and operational forecast models in that region now use such climate-informed methods routinely (e.g., [25]). Conversely, the Colorado River Compact, based on a short record of early twentieth-century instrumental observations that was later discovered to represent a period of anomalously high flow in the US southwest, led to water supply over-allocations so severe that the river now barely runs to its mouth across the international border in Mexico (e.g., [11,52,74]).…”

A non-uniqueness problem in the identification of power-law spectral scaling for hydroclimatic time series

“…Fleming et al , 2007 or forecasting (e.g. Hamlet et al 2002, Gobena et al 2013 contexts, and a growing number of applications to subsurface water resources as well (e.g. Quilty 2006, Gurdak et al 2007).…”