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<br />back to Vernal. The number of zooplankton in each sample was determined by subsampling the <br />total contents. The total zooplankton sample was put into a petri dish with equal grids outlined <br />on the bottom of the dish. The total contents were spread throughout the dish and the numbers <br />present in randomly selected grids were counted to extrapolate the total number present. The <br />density of zooplankton was estimated by dividing the total number of zooplankters collected by <br />the water volume sampled. <br /> <br />Results <br />In 1994, average daily flows at Jensen never exceeded 340 m3/s and did not overtop the <br />dike at Old Charley Wash. As a consequence, Old Charley Wash never exceeded 1.6 m in <br />maximum depth in 1994 (Figure 2). In 1995 and 1996 the average daily flows at Jensen <br />exceeded 396 m3/s between 21 May and 2 July (48 days), and 8 May and June 14 (38 days), <br />respectively. During both 1995 and 1996 maximum depth exceeded 2.0 m. Due to a declining <br />water elevation in Old Charley Wash from seepage and evaporation, river water was augmented <br />by pumping water beginning the first week of July, 1994. Water was augmented at a rate of 0.6 <br />m3/s for eight hours per day for two weeks (5 days/wk) and every other week thereafter to <br />maintain a maximum depth of approximately 1 m. No water was added to the wetland in 1995 or <br />1996. During the low flow year of 1994 temperatures in the main channel (Jensen gage) were <br />similar to wetland temperatures measured during the daylight hours after 1 June (Figure 2). <br />However, temperatures in the wetland were warmer than the river by several degrees on 24 May <br />and 7 June. During both 1995 and 1996 water temperatures were warmer in the wetland than the <br />river throughout the spring and summer. <br />Although turbidity was generally higher in the spring than summer, it showed no direct <br />relationship to inundation of the wetland by the river through time (Figure 2). Values observed <br />in the low flow year of 1994 were similar to those observed in both high flow years. The highest <br />value observed in the study (212) occurred on June 13, nearly three weeks after inundation to the <br />wetland to the river. Rarely did values exceed 50 NTU's during the study. Therefore, sediment- <br />rich water entering the wetland appeared to settle quickly in the basin and the water column <br />remained fairly clear even when the wetland was connected to the river. <br />Dissolved oxygen (DO) remained high during all three years ofthe study. Maximum <br />surface DO occurred in August 1994 and July 1995 (Figure 2). Few DO observations were made <br />in 1996, but those values were relatively high. Differences were observed in surface and bottom <br />DO measurements in late June and early July 1996. <br />Highest conductivity values were observed when Old Charley Wash was first filling and <br />is reflective of runoff conditions in the river (Figure 3). During 1994 and 1995 conductivity <br />values slowly increased over time and was probably related to evaporation. No such increase <br />was observed in 1996; however, based upon changes in water elevation, little evaporation <br />occurred in 1996. Alkalinity ranged between 150 and 10 mg/l CaC03 (Figure 3). The only <br />recognizable pattern was a noticeable drop in alkalinity in the fall, which was probably associated <br />with DO and pH related to changes in macrophyte metabolism. No values of either conductivity <br />or alkalinity appeared inhibitory to biotic processes. <br />Although differences occurred in spring runoff patterns among years, peak zooplankton <br />quantities appeared between the third and fourth week of June during each year of the study <br />(Figure 4.) Peak mean number of zooplankton per liter was 54.3 in 1995 and 42.8 in 1996. <br /> <br />13 <br />