In 2003, the Poplar River Bilateral Monitoring Committee decided to suspend much of the water-quality 

 sampling program until it is warranted again. This suspension applied to all surface-water-quality 

 sample collection activities by Environment Canada at the East Poplar River boundary station. The 

 Committee has agreed to use the daily conductance data collected by the specific-conductance monitor 

 as a surrogate for the monthly water-quality sampling program. Therefore, only four water-quality 

 samples were collected for TDS and boron by the USGS in 2005. Hence, the three-month FWC for TDS 

 and boron in 2005 were calculated using the two established equations (shown later in text) and the daily 

 conductance data collected by the specific-conductance monitor installed at the East Poplar River at the 

 International Boundary. 



The Bilateral Monitoring Committee adopted the approach that, for the purpose of comparison with the 

 proposed IJC long-term objectives, the boron and TDS data are best plotted as a five-year moving FWC 

 which is advanced one month at a time. 



Prior to 1988, long-term averages were calculated for a five-year period in which 2.5 years preceded and 

 2.5 years followed each plotted point. Beginning in 1988, the FWC was calculated from the 5-year 

 period preceding each plotted point. For example, the FWC for December 2005 is calculated from data 

 generated over the period December 2000 to December 2005. The calculations are based on the results 

 of samples collected throughout the year, and are not restricted to only those collected during the months 

 bracketing the period of irrigation (March to October) each year. 



3.2.5.1 Total Dissolved Solids 



TDS is inversely related to streamflow at the East Poplar River at the International Boundary station. 

 During periods of high runoff such as spring freshet, TDS decreases as the proportion of streamflow 

 derived from ground water decreases. Conversely, during times of low streamflow (late summer, winter) 

 the contribution of ground water to streamflow is proportionally greater. Because ground water has a 

 higher ionic strength than the surface water entering the river, the TDS of the stream increases markedly 

 during low-flow conditions. 



10 



