Watershed Conditions Statements

Rain presently falling is causing flows in the Rideau River to increase toward thresholds at which flooding can be expected to cause access issues to lower lying waterfront properties. The area first affected will be the Long Reach of the Rideau between Kars and Kemptville. In particular, access to Hilly Lane, Cedar Beach, Rideau Glen and other neighbourhoods on that reach of the river can be expected to be compromised as the rain enters the system today. Rain forecast in the order of fifty-five millimetres (mm) on Thursday and Friday can be expected to be followed by a peak on…
Rain presently forecast for this week is expected to cause a significant increase in flows and water levels, potentially to 1:4 year frequency (flow that has a 25% probability of occurrence in any year). There is still some snow in the Rideau River watershed which will be much reduced today with the arrival of temperatures above 10 degrees. This will increase flows slowly through the day. Twenty millimetres of rain now forecast for Tuesday will cause further increases. Fifty millimetres of rain on Thursday and Friday can be expected to bring a peak on Saturday possibly in the range of…
Cold temperatures have slowed runoff and will cause declining water levels in watershed lakes and streams through the weekend. There is enough water moving through the system from the melt and rain that flows are still increasing in some tributaries. This will tail off today and levels can be expected to decline through the weekend. Weather forecasts indicate another warmup with some rain next week that could cause flows to increase again. The warm temperatures and increased flows caused the ice on all waterbodies to become unstable. With refreezing occurring, new ice will be forming. However, it will take a…
 Warm temperatures and rain could cause water levels to threaten access to lower lying communities. This message applies particularly to Hilly Lane, Cedar Beach and Rideau Glen and other small communities along the Long Reach of the Rideau River near Kemptville that are susceptible to flooding. The Hilly Lane community could start to have water encroaching on the access road by Wednesday as a result of above zero temperatures melting the remaining snow and a two-day total rainfall of as much as 20 millimetres. Fortunately, temperatures are forecast to fall below freezing by Wednesday night which can be expected to…
Daytime temperatures above freezing forecast for the weekend and into next week will cause melting and increased levels on watercourses throughout the Rideau River watershed. Above freezing temperatures will cause ice and snow melt over the next several days. There is sufficient snow on the ground in the lower part of the watershed to absorb most of the meltwater. However, areas to the south and west of the City of Ottawa, where there has been less snowfall, can be expected to have more runoff. In all cases, the ice cover can be expected to become unstable to various extents with…
The drought status in the Rideau River watershed is being downgraded to “Minor” because the recent warm temperatures and precipitation have caused flows to increase significantly in watershed streams.Rain and snowmelt have caused flows in some streams to approach and, in some cases, exceed the long-term historical average flows. Kemptville Creek had low flows of .028 cubic metres per second (cms), 1.5% of average, in mid-October. Occasional thaws with rain since then have caused flows to increase in all streams and fluctuate around the average. Kemptville Creek flows have been consistently elevated since December 27 and reached three times the…
The drought status in the Rideau River watershed is being downgraded to “Moderate” because recent precipitation has generally increased flows in area streams.  Kemptville Creek flows are about 130% of the historical average, or normal, for the time of year as a result of October rain and November snowmelt. Other recorded streamflows are above 60% of normal which has led to the downgrade of the drought status. However, the Tay River out of Bobs Lake has not had the same precipitation and is at only 10% of the normal flow. This indicates that the drought is not fully over despite…
The drought status in the Rideau River watershed remains at “Severe” because sustained flows in the streams and rivers have not been restored. As has been the case all summer, rainfall has been very erratic with significant amounts recorded at some monitoring stations and very little at others. There has been enough rain in the last two weeks to make many watershed residents forget that there is still a drought. Lawns are green. Farm crops are close to being ready for harvest.
Recent heavy but localized rain was not sufficient to change the drought status in the Rideau River watershed from “Severe.” Streamflows and lake levels continue to decline throughout the watershed. At the climate station at Kemptville, 44 millimetres of rain was recorded on September 10. Both Smiths Falls and Rideau Ferry received 26 but all of 2 mm was recorded at the station at Innisville east of Perth. Where the heavier rainfall occurred, levels increased but they quickly fell back to where they had been.
Sporadic and random rainfall over the last week was not enough to bring the Rideau River watershed out of the Severe Drought status reached in mid-August Previous rain in August did cause flows and levels to increase but only for a brief period. With rain coming in small cells that affected very limited areas, levels have quickly declined again. Forecast for this week has a total of 20 millimetres possible that will not have a significant impact.
Despite the recent rainfall, the Rideau Valley remains in a Severe Drought Status. The 90-day accumulation of rainfall recorded at Environment Canada climate stations in and around the Rideau River watershed has increased to an average of 82 percent of the historical average. The 30-day accumulation is about 99 percent.
Based on the 30 Day Precipitation drought indicator, the Rideau River Watershed is in the “Severe” Drought category. There has been no rain recorded at the Ottawa Airport since July 25. Some rain has been recorded at other locations in and around the watershed but there have not been the several days of rain needed to restore the deficit that has accumulated. There is rain forecast through Friday and Saturday but that is expected as thunderstorms which will not produce the needed general rain over the whole watershed. Warm weather is forecast to continue through next week which will cause…
With little rain over the last two weeks, the Moderate Drought conditions continue in the Rideau watershed. The accumulated precipitation over the last 90 days is less than 60% of the long term average for this time of year which is the threshold for Moderate Drought. No significant rain is presently in weather forecasts for the next week but hot temperatures are. This means that evaporation will be a significant component of the water level decline process throughout the watershed.
The precipitation indicator for Moderate Drought of 60% of normal was reached last Sunday. Rainfall since then has had a minimal impact and conditions remain very dry. Flows in the Rideau River at Ottawa are at 25% of normal for the time of year. Two of the major tributary streams, Jock River and Kemptville Creek, are both flowing at about 6% of normal. The Tay River is in relatively better shape benefitting from outflow from Bobs Lake, one of the Rideau Canal reservoir lakes. Smaller streams are intermittent or dry and aquatic habitat is compromised for all species.
With no rain until Monday in weather forecasts, it is expected that the drought status for the Rideau River watershed will pass the threshold from Minor to Moderate Severity by Sunday. The amount of rain forecast for Monday will do little to reverse the trend of deepening drought. Flows in the Rideau River at Ottawa are 15% of normal for the time of year. Larger tributary streams are about 6% of normal and many small streams are intermittent or dry. Aquatic habitat is becoming limited for all species.
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Address:
Rideau Valley Conservation Authority
3889 Rideau Valley Drive
Manotick, Ontario K4M 1A5

Phone:
613-692-3571, 1-800-267-3504

Email:
info@rvca.ca

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Monday to Friday, 8:30 a.m. to 4:30 p.m.

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