May 17, 2013 update

Upper Thames River Watershed moves out of Low Water Conditions

The Upper Thames River watershed is no longer in Low Water Conditions, for the first time since April 2012. Low water conditions are evaluated by looking at several indicators, including precipitation, stream flows and groundwater levels.

The overall picture is positive:

• April precipitation totals - Above Normal across the Upper Thames watershed,
• 3-month (February-March-April) precipitation totals in the watershed - relatively Normal,
• 30 day average stream flows - Above Normal at the end of April at the majority of stream gauges monitored for this program, and
• average April groundwater levels - Normal to Above Normal in the majority of wells monitored for this program.

More detailed information follows:

April (1 month) precipitation:

• April was a wet month with many wet days; greater than 10mm of rainfall was recorded by at least one UTRCA gauge across the watershed on over one-third of the days in the month;
• Approximately half of April precipitation was recorded during five consecutive days of rainfall on Apr. 8-12, with the majority of UTRCA gauges across the watershed recording approximately 50 to 80mm of precipitation over the 5 day period.
• Overall, April precipitation totals were Above-Normal across the entire Upper Thames watershed, with precipitation totals recorded at the majority of UTRCA gauges ranging between 110% to 160% of normal precipitation for the month.

February-March-April (3 month) precipitation:

• From the previous update, February total precipitation was relatively normal, and March total precipitation was significantly below normal, across the Upper Thames watershed.
• Reviewing data from the two weighing gauges in the watershed, 3-month (February-March-April) precipitation totals in the Upper Thames watershed were relatively Normal, with precipitation totals at both gauges approximately 105% of normal.

Stream flows:

• 30 day average stream flows ended the month of March at relatively normal levels at the majority of stream gauges monitored for this program.
• The rainfall received in April contributed significantly to stream flows such that 30 day average stream flows were Above Normal (greater than 75th percentile) at the end of April at the majority of stream gauges monitored for this program.
• Of note, throughout the first four months of the year (Jan-Feb-Mar-Apr), 30 day average stream flows remained in the Normal to Above Normal ranges at the majority of stream gauges monitored for this program.

Groundwater levels:

• In late April and early May, groundwater data was manually collected from a subset of monitoring wells in the Upper Thames watershed by UTRCA staff.
• In response to the significant rainfall received in April, groundwater levels continued to recover during the month in all of the wells monitored for this program, (after being significantly Below Normal for an extended period in the second half of 2012 and continuing Below Normal in early 2013).
• The net result of recovering groundwater levels was that, average April groundwater levels were Normal (25th to 75th percentiles) to Above Normal (greater than 75th percentile) for the time of year in the majority of wells monitored for this program.
• Please note that, similar to most areas of the Province, groundwater monitoring records extend back only approximately 10 years for the majority of wells in the Upper Thames watershed.

April 23, 2013 update

Upper Thames Watershed remains in Level 1 Low Water Conditions

The Upper Thames River watershed remains in Level I Low Water Conditions, after a review of precipitation, stream flows and groundwater levels revealed the following:

Precipitation:

• March precipitation totals were well below normal across the Upper Thames watershed, ranging between 45% to 60% of normal for the month.
• The 3-month (January-February-March) precipitation totals were relatively normal, ranging between approximately 85% to 95% of normal.

Stream flows:

• The significant rainfall/snowmelt event in the first half of March, and melting of the remaining snowpack in the second half of the month, contributed significantly to stream flows such that 30 day average stream flows were in the normal range (25th to 75th percentiles) throughout March at the majority of stream gauges monitored for this program.
• Of note, throughout the first three months of the year (Jan-Feb-Mar), 30 day average stream flows remained in the normal to above normal ranges at the majority of stream gauges.

Groundwater levels:

• In early April, groundwater data was collected from monitoring wells in the Upper Thames watershed by UTRCA staff. In contrast to the automated data collection system for UTRCA precipitation and stream flow data, groundwater data in the Upper Thames watershed requires manual collection from each monitoring well; hence, it is more challenging for UTRCA to collect and report on groundwater data than precipitation or flow data.
• In response to the melting snowpack throughout March, groundwater levels continued to recover during the month in the majority of wells monitored for this program, after being significantly below normal for an extended period in the second half of 2012. Because groundwater typically rises in the early spring, the recovering groundwater levels in March needed to rise significantly to reach normal levels for the time of year.
• The net result was that, although groundwater levels continued to recover during the month, average March groundwater levels were below normal for the time of year in the majority of wells monitored for this program, with groundwater levels in several of the wells continuing to be the lowest on record for the time of year. Please note that, similar to most areas of the province, groundwater monitoring records extend back only approximately 10 years for the majority of wells in the Upper Thames watershed.

Overall, average stream flows have remained at normal to above normal levels across the Upper Thames watershed for the past several months. However, March precipitation totals were well below normal across the watershed and, although groundwater levels continued to recover during the month, average March groundwater levels were below normal for the time of year in the majority of wells monitored for this program (with groundwater levels in several of the wells continuing to be the lowest in the last 10 years for the time of year). Therefore, the Upper Thames watershed remains in confirmed Level I Conditions at this time.

March 13, 2013 update

Upper Thames Watershed moves to Level 1 Low Water Conditions

The Upper Thames watershed is moving from a confirmed Level 2 Condition to a confirmed Level 1 Condition at this time, due to the following considerations:

• 1-month (Feb) and 3-month (Dec-Jan-Feb) precipitation totals were normal in the watershed,
• 30 day average stream flows were normal to above normal across the watershed throughout the past two months (Jan-Feb), and
• groundwater levels improved significantly in February in a majority of the wells monitored for this program, with groundwater recovering to normal levels in half of the wells monitored for this program.

However, concern remains for groundwater because, as of late February, groundwater levels continued to be below normal in half of the wells monitored for this program, with groundwater levels in several of the deeper wells continuing to be the lowest in the last 10 years for the time of year.

The watershed had been in Level 2 Low Water Conditions since May 2012.

January 29, 2013 update

Groundwater Remains Low Due to Dry 2012

The upper Thames River watershed remains in a Level 2 Low Water Condition because groundwater levels are significantly below normal.

Based on 10 years of monitoring wells for this program, groundwater levels continue to be the lowest or near the lowest on record for this time of year throughout the watershed. Groundwater monitoring results indicate that the upper Thames watershed has not fully recovered from the significant low water conditions of 2012.

Total precipitation recorded in 2012:

• Approximately 65% of normal, with a total precipitation deficit for the year of over 300 mm
• Lowest annual total recorded at the Environment Canada - London Airport gauge since the early 1960s

The story is different for surface water. Stream flows recovered to near normal levels in late December and early January at most of the stream gauges monitored by the UTRCA. The watershed has received near normal amounts of precipitation over the past three months, which has provided some recovery from last year’s low water conditions. The UTRCA hopes that this trend of normal precipitation continues through the winter and that there is a similar recovery for groundwater.

May 3, 2012

Record-breaking Dry Spring Continues

Upper Thames Watershed moves to Level 2 Low Water Condition

The ongoing dry conditions have prompted the Upper Thames River Low Water Response Team (LWRT) to move the Upper Thames River watershed to a Level 2 Low Water Condition.

A Level 2 Low Water Condition is part of a three-tiered advisory system used in Ontario to inform the public of local low water conditions. The LWRT had declared the least severe level, a Level 1, in early April.

Low water conditions are evaluated by looking at several indicators, including precipitation over the past three months, and stream flows over the past month.

“April’s precipitation totals were significantly below normal across the watershed,” explained Mark Shifflett, Senior Water Resources Engineer with the Upper Thames River Conservation Authority (UTRCA). “Our rain gauges measured only 25% to 35% of the rain that we would normally get in April.”

Environment Canada’s London Airport gauge recorded 25.6 mm of total precipitation in April, which is the lowest April total in over 60 years.

April was the watershed’s third straight month of below normal precipitation. As a result, flows in the Thames and its tributaries continue to fall. “Average stream flows fell to record low levels for the month at nearly all our stream gauges,” said Shifflett.

Specialists at the UTRCA say the ongoing dry conditions may have an impact on water quality and aquatic animals.

“Runoff from rain is one of the main ways that pollutants are carried into a stream,” explained Karen Maaskant, Water Quality Specialist. “With the dry conditions this spring there has been much less of this type of pollutant runoff to streams. However, without higher flows to flush the stream, any accumulated sediment and pollutants in the stream bed are not being pushed through the system as would normally occur.”

Aquatic Biologist John Schwindt picked up on this concern. “A lot of aquatic habitat will be covered with silt because we haven’t had spring runoff and high flows to scour away this silt. The result is limited and poorer habitat for the invertebrates that form the basis of the food chain, and impaired spawning habitat for many fish species.”

“Low water levels also impede the movement of many migratory fish species and may prevent them from getting to their preferred spawning habitat,” Schwindt said. “As most of our fish species spawn in the spring and early summer, continued low water will make much of the spawning habitat inaccessible or unusable and spawning fish more vulnerable to predators.”

If the drought continues, Maaskant expects to see more algae growth, especially in stagnant areas of the river. Algae growth reduces oxygen available for aquatic life.

To add to this concern, the UTRCA’s flow augmentation reservoirs at Wildwood (St. Marys) and Pittock (Woodstock) are below normal ranges for this time of year. Those two reservoirs have normally filled by this time with snow melt and spring rains. Those reservoirs are used in the summer months to augment flows in the North and South Thames River.

The dry conditions may also start to affect people with wells. “We have seen a general trend in our groundwater monitoring system of below normal water levels not only in shallower wells, but also in some deeper wells,” said Linda Nicks, UTRCA Hydrogeologist.

“People have asked me how much rain it will take to recover,” said Shifflett. “Right now, we’re at a rainfall deficit of 120 mm for the year. It will take some time to recover from that large a deficit.”

Find our more about current watershed flow and meteorological information and the LWRT.

Contact: , Senior Water Resources Engineer