Research Document - 1999/188

Hydrological Conditions for Atlantic Salmon Rivers in the Maritime Provinces in 1997.

By C. Caissie

Abstract

This paper provides recent (1997) and historical information on hydrological conditions for selected Atlantic salmon (Salmo salar) rivers within the Maritime Region of DFO. High and low flow for each river were calculated based on historical annual high and low flow series. Stream water temperatures were reported in 10 river systems.

Discharges were above normal in January with NB rivers experiencing excessive monthly flow conditions. March and April showed below normal flows for rivers in NB and part of NS. Such below normal conditions in March and April resulted in a one month delay for high flows. In fact, excessive flows were observed May for most of the region. The spring breakup of 1997, although later than normal, was generally characterized as average with most rivers having floods between a 2-year and 5-year flood event. NS rivers showed less severe spring floods with flows lower than a 2-year event. A few rivers showed higher spring peaks such as the Saint John River which reached a 10-year flood and Wilmot River at above the 5-year event.

Low flow conditions in 1997 were similar throughout the area with low discharges from July to the end of October. Deficient flows persisted to the end of 1997 for some rivers with record lows in December (Nashwaak, SW Miramichi and Wilmot Rivers). On a daily basis, low flows of 1997 were between a 2-year and 5-year event with only LaHave River showing lower flows than the 5-year event.

River water temperatures in 1997 were characterized by minor high temperature events between late June and mid-August. Tobique Fishway reached its peak water temperature on July 3 at 24.1°C, Mactaquac Fishway on July 21 at 22.9°C, Nashwaak River on July 27 at 26.6°C and Kennebecasis River on August 11 at 20.6°C.

In the Miramichi River basin, most rivers reached their peak water temperature around mid-August (10-11); Catamaran Brook (17.6°C), Little Southwest Miramichi River (24.9°C), Northwest Miramichi River below Big Hole (26.2°C); Southwest Miramichi River at Sister's Brook (23.4°C) and Northwest Miramichi River at the Barrier Fence (19.8°C). Dungarvon River reached its peak temperature on July 27 at 23.4°C while Northwest Miramichi River at Eel Ground recorded its peak on July 7 at 26.8°C.

The study of a flow variability score on the Southwest Miramichi River to quantify abnormal events showed that over the past 8 years it varied between 6 and 13 with high values in recent years. Flow variability was signficantly related to adult salmon returns.

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