Watershed Conditions Statements

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.
The last significant rainfall in the Rideau River watershed on June 5 caused streamflows to increase and helped crop growth, but the effect has worn off and the lack of rain since has once again left flows dropping and crops in need of more water. Rainfall recorded at Kemptville indicates that the Moderate Drought severity has been reached in the southern parts of the watershed. However, the drought severity overall in the watershed is still Minor but is expected to reach Moderate status late next week. Forecast rain next week is not expected to have a significant impact. Streamflows increased…
Rain on June 5 was sufficient to improve the drought status to minor severity on the Rideau watershed. Streamflows and water levels increased as a result of the rain from about 10 percent of normal for the time of year to 50 percent. However, such flows are typically seen in mid-July to early August. Little rain is forecast for the next two weeks which means that water levels can be expected to drop noticeably throughout the watershed again.
With little effective rainfall on the Rideau watershed for the last two months, the drought status is now moderately severe. Except for some intense rainfall in the downtown core of Ottawa last Friday and Saturday, conditions have continued to be very dry in the Rideau River watershed. Rainfall recorded at Environment Canada climate stations over the last three months is now at 60% of normal for the time of year. This means that Moderate Drought status has been reached.
With no rain over the last ten days and less than 30% of normal for the last 30 days, the Rideau River watershed is on the verge of minor drought conditions. Precipitation measured at Environment Canada climate stations in and around the watershed show that about 80% of normal for the time of year has fallen in the last 90 days. This means that minor drought status has been reached. Municipal watering restrictions could be imposed to limit the volume of water extracted from groundwater and surface water sources. It is recommended that those living in residences served by private…
With a definite declining trend of the water levels of Bobs Lake and Christie Lake, the Flood Watch that has been in effect specific to those lakes since April 11 is now cancelled. With little precipitation over the last two weeks and, therefore, declining inflow to contend with, Parks Canada staff have been able to gradually bring the levels of both lakes back down to target operating ranges. Water levels in the rest of the watershed are also decreasing and are close to averages for the time of year. However, the water is still relatively high and is cold. Caution…
The focus of this message is potential flooding issues on Bobs and Christie Lakes in the upper end of the Tay River watershed, part of the Rideau River/Canal system. Bobs Lake has levelled off over the weekend as inflows were reduced by colder temperatures. Runoff from the snow that fell overnight along with rain showers today and Tuesday will prolong the high water levels. No precipitation along with more spring-like temperatures are forecast for the rest of the week beyond Tuesday. This can be expected to bring a decline in levels on both Bobs and Christie Lakes.
An unusual amount of snow for this time of year is expected to cause lake levels in the upper part of the Rideau River watershed to rise as the snow melts over the next several days. Water levels can be expected to increase throughout the watershed but levels to flood stage could occur on Bobs and Christie Lakes. With the level of Bobs Lake close to the Full Supply Threshold, water has to be released. However, the release is being done as gradually as possible to minimize the impacts on both lakes. While levels are likely to increase downstream of…
Flows in all watercourses in the Rideau River watershed can be expected to increase through today as a result of a significant rain event. Forecasts of heavy rains today in the province east of Georgian Bay will have an impact on the Rideau River watershed. With rainfall in the order of 30 mm possible, flows can be expected to increase again to similar flows as what was reached earlier in March. This could once again bring flooding of the lowest lying areas along rivers and streams and on lakes and ponds.
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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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