Long-term Water Level Fluctuations Research Articles

Effects of Lake Michigan Water Levels on Wetland Soil Chemistry and Distribution of Plants in the Straits of Mackinac

The effects of short-term or summer season water level fluctuations on wetlands were determined from measurements of flooding, relative soil chemistry, and the presence of plants. Analyses demonstrated higher relative concentrations of plant-available soil nutrients and higher density of plants on flooded emergent wetlands as compared to infrequently flooded, unconsolidated shore sites. Flooding resulted in anaerobic soil conditions and increased concentrations of nutrients for wetland plants. The density of emergent wetland plants was highest where the topographic conditions and water level led to duration of flooding between 50 and 85% of the growing season. The effects of long-term water level fluctuations on wetlands were measured from historical aerial photographs of low, average, and high lake level conditions (1938 to 1980). An increase in water levels of 0.3 m reduced the extent of coastal wetlands by 18%. Historical aerial photos demonstrated and a model predicted that 13% of the total wetlands measured at low lake levels remained in the study area at the highest lake level sampled. This result was verified during the high lake levels of May 1985.

WATERFOWL PRODUCTION AND WATER LEVEL FLUCTUATION

Water level fluctuation is probably the most significant environmental factor influencing waterfowl production. The three basic life processes of waterfowl in Canada, breeding, moulting and staging, are all affected by water level changes in the long and short term. The impact of water level fluctuations on breeding success is the most important way in which waterfowl production is influenced. Habitat suitability for waterfowl tends to reflect long-term water level fluctuations while habitat utilization can be affected in the short term by seasonal and annual changes in water level. The importance of magnitude, direction, rate and timing of water level fluctuations in determining waterfowl breeding success is discussed. Although waterfowl have developed a number of adaptations to cope with water level fluctuations, these responses are normally not completely effective and result in some degree of decreased production. Although having a number of negative impacts on waterfowl production, water level fluctuation is essential for the long-term maintenance of wetland productivity.

HYDROGEOLOGY AND YIELD EVALUATION OF A MUNICIPAL WELL FIELD, ALBERTA, CANADA

ABSTRACT The present study is based on field exploration and production records. The producing formation consists of consolidated continental sediments which are overlain by clays, sands and gravels. No areally extensive aquifers can be distinguished. The only zone of consistently high permeability is associated with a buried channel in the bedrock and is interrupted by a hydraulic barrier. Salt concentrations in the groundwater range from less than 500 ppm to over 2000 ppm. Groundwater temperatures range form 38 °F (3·3 °C) to 41 °F (5·0 °C). The sustainable yields of individual wells of the three-well field range from 60 igpm to 150 igpm with a combined maximum of 350 igpm. Pumping creates an elongated hydraulic depression which is interrupted by the barrier in one direction and causes major changes in water levels 2 miles distant in the other direction. Short and long-term water-level fluctuations suggest two sources of recharge: direct infiltration and lateral flow. Significantly different values of transmissivity (T) are computed from production tests of different lengths. Tests of duration of 10 to 500 min, 70 to 130 h, and several months yield values for T, in igpd/ft, of 10,000 to 50,000, 2000 to 6000, and 1300, respectively. From the three methods of attempted yield evaluation the one based on empirical relations between operating pumping rates and drawdowns yields the most satisfactory results.