Reservoirs are valuable as temporary or seasonal sources of stock water.� They are dependent on surface runoff or seepage causing losses and/or reduction in quality water from spring to fall.� Contact with mineral soil may add solutes to retained water while evaporation may act to concentrate solutes.� Cattle moving and standing in retained water can cause suspension of organic and inorganic matter.� The objective of this study was to determine if the concentration of total dissolved solids (TDS) in catchment water systems with simultaneous cattle use were influenced by frequency of precipitation events characterized by the months.� To estimate spring/summer variation in water TDS concentrations, 2 livestock reservoirs (Upper Flood near the eastern boundary and North 4 adjacent to the southern property line) were fitted with Troll 9500� continuous monitoring submerged TDS sensors in June through August 2016 and 2017 at the 22,257 ha USDA-ARS Fort Keogh Livestock and Range Research Laboratory near Miles City, MT.�� Two sensors recorded a reading hourly at a depth of 2 feet in each reservoir.� Data were analyzed as a completely randomized design testing the effect of year, site, month, and their interactions on TDS concentration using Proc. Mixed (SAS 2014).� There was a significant year*site*month interaction (P < 0.01). The concentration of TDS was highest in August in North 4 reservoir in both years (avg 1406 � 5.5 ppm) and lowest in the Upper Flood reservoir in June in both years (avg 538 � 5.5 ppm). Average concentrations of TDS increased 25% from June to July 16% from July to August and 63% from June to August.� Water TDS content was different between the 2 reservoirs and increased during summer months.�� �To avoid productivity declines these results suggest monitoring water quality maybe important across time and location.
Oral presentation and poster titles, abstracts, and authors from the Society for Range Management (SRM) Annual Meetings and Tradeshows, from 2013 forward.