CLIMATIC AND HYDROLOGIC VARIABILITY IN A COASTAL WATERSHED OF SOUTHWESTERN BRITISH COLUMBIA¹

Abstract

Climate data from the Malcolm Knapp Research Forest (MKRF) in the Coast Range mountains of southwestern British Columbia were used to examine relationships between climate and hydrology and variations in the El Niño Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO). Air and water temperatures were higher and precipitation was lower during in‐phase or warm PDO/E1 Niño events than in other years. In contrast, in‐phase or cool PDO/La Niña years were generally cooler and wetter than other years. Precipitation and East Creek discharge were positively related to the Southern Oscillation Index (SOI) and negatively related to the PDO index. Conversely, air and water temperatures were negatively related to the SOI and positively related to the PDO index. Differences in precipitation and air temperature were also evident at longer time scales when separated by PDO phase. Because of drier conditions during in‐phase El Niño events, the flow of organic matter from East Creek to downstream portions of the channel network was lower compared to other years. This reduction has implications for downstream communities, as these subsidies provide a major source of energy for stream food webs. Therefore, short term and long term shifts in climate, discharge, and water temperature may have profound impacts on the ecology of Pacific Northwest (PNW) watersheds due to changes in a number of ecosystem processes such as altered flux of organic matter from headwater streams to larger rivers.

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

“…Hartmann and Wendler (2005) also indicated the importance of accounting for such changes in analyses of long-term climate variations and change. Kiffney et al (2002) assessed long-term climate variability in a south coastal BC watershed. They found that air temperature was higher during warm PDO/El Niño, and cooler during cool PDO/La Niña.…”

Response of a fractured bedrock aquifer to recharge from heavy rainfall events

“…One of the most established modulations is that of PDO on ENSO, which results in El Niño (La Niña) being strong and stable when PDO is positive (negative) (Kiffney et al, 2002;Whitfield et al, 2010;Gershunov and Barnett, 1998). During these occasions, PDO and ENSO are said to be in-phase, or constructive (Kiffney et al, 2002).…”

“…PDO and ENSO are said to be out-of-phase, or destructive, during the inverse phases (Kiffney et al, 2002). Constructive phases produce a strong, coherent precipitation response and destructive phases produce a weakened, spatially incoherent response (Gershunov and Barnett, 1998).…”

“…Constructive phases produce a strong, coherent precipitation response and destructive phases produce a weakened, spatially incoherent response (Gershunov and Barnett, 1998). For example, Gershunov and Barnett (1998) Kiffney et al (2002) found that winter precipitation during years associated with La Niña and cool, negative-phase PDO was 19-25% higher than non-ENSO related and out-of-phase paired years, and 39% higher than years with El Niño and warm, positive-phase PDO.…”

Effects of Logging Second‐Growth Forests on Headwater Populations of Coastal Cutthroat Trout: A 6‐Year, Multistream, Before‐and‐After Field Experiment

“…We report on study results for the first 6 years involving instream physical habitat and fish size and abundance, and we summarize specific aspects of stream temperature and discharge. Detailed results for instream chemical, water volume, and thermal variables; climate; and measures of nonfish aquatic biota (primary production, invertebrates) and terrestrial biota (insects, amphibians, mammals) are in preparation or reported elsewhere (e.g., Kiffney et al 2000Kiffney et al , 2002Kiffney et al , 2003Cockle and Richardson 2003;.…”