Marsh Ecology Research Program (MERP): Water table levels (1982-1989)

The Marsh Ecology Research Program (MERP) was a long-term interdisciplinary study on the ecology of prairie wetlands. A scientific team from a variety of disciplines (hydrology, plant ecology, invertebrate ecology, vertebrate ecology, nutrient dynamics, marsh management) was assembled to design and oversee a long-term experiment on the effects of water-level manipulation on northern prairie wetlands. Ten years of fieldwork (1980 -1989), combining a routine long-term monitoring program and a series of short-term studies, generated a wealth of new and diverse information on the ecology and function of prairie wetlands (Murkin, Batt, Caldwell, Kadlec and van der Valk, 2000). This data set includes water table levels, collected as part of the hydrology section of MERP.

Studies of marsh ecosystems are frequently hampered by inadequate information about water budgets (Carter et al., 1979). Marshes are often open systems, particularly with respect to movement of water and associated particulate and dissolved materials (Kadlec, 1983). Efforts to evaluate the plant-nutrient relationships in such systems are contingent on knowledge of the hydrology of the system (Kadlec, 1979). Accurate estimates of water budgets are also essential pre-requisites for studies of wetland ecosystem nutrient cycles. Hence, the objective of the measurements described below, together with weather and water level/volume data, was to provide water budgets for nutrient budget calculations for the Marsh Ecology Research Program (MERP; Kadlec, 1989). The approach to hydrology used was the concept of mass balance:

Inputs - Outputs = change in volume

For this approach, all 3 terms had to be estimated. Change in volume was calculated from daily records of water level and water level - volume tables. Inputs of water to diked cells can be in 3 forms: precipitation, water pumped to maintain design levels, and seepage through the dike or sand ridge forming the north end of the cells. Precipitation inputs were calculated from weather records and pumping was metered, providing direct measurement. Seepage was estimated by difference, with checks based on groundwater topography and hydraulic conductivity, as well as seepage meter spot checks. Outputs of water were evapotranspiration, pumping, and seepage. Seepage out was also derived primarily by difference. Because the hydrologic characteristics of different cells in different years were replicated, estimates of the standard error in the seasonal water budgets were possible and proved to be 10% or less (Kadlec, 1989).

In order to refine estimates of the inputs and outputs for the water budget of the cells, additional physical measurements were made. These factors were monitored in order to more accurately define the water storage of the cells, groundwater levels, and losses through seepage. The additional monitoring programs included: supplementary groundwater sampling adjacent to cells for nutrients, and monitoring water storage in the cells (Kadlec, 1989). The groundwater monitoring program was organized on a seasonal basis, due to the more gradual shift in groundwater makeup and supply. Sampling was done monthly for water table level and nutrients in conjunction with the regular groundwater sampling within the cells, and twice during the season for hydraulic conductivity.

Note: additional hydrological data sets collected as park of MERP (i.e. water levels, pump meter volumes, precipitation, evaporation) are contained in separate data packages on the KNB.

For further information on the Marsh Ecology Research Program (MERP), please visit: http://www.ducks.ca/conserve/research/projects/merp/index.html

References:
Carter, V., M.S. Bedinger, R.P. Novitski and W.O. Wilen. 1979. Water resources and wetlands. In: Wetland Functions and Values: The State of Our Understanding. (Eds.) P.E. Greeson, J.R. Clark and J.E. Clark, pp. 344-376. American Water Resources Association: Minneapolis, Minnesota.
Kadlec, J.A. 1979. Nitrogen and phosphorus dynamics in inland freshwater wetlands. In: Waterfowl and Wetlands: An Integrated Review. (Ed.) T.A. Bookhout, pp. 17-41. North Central Section, The Wildlife Society.
Kadlec, J.A. 1983. Water budgets for small diked marshes. Water Resources Bulletin 19: 223-229.
Kadlec, J.A. 1989. Hydrology. In: Marsh Ecology Research Program: Long-term Monitoring Procedures Manual. (Eds.) E.J. Murkin and H.R. Murkin, pp. 8-11. Manitoba, Canada: Delta Waterfowl and Wetlands Research Station.
Murkin, H.R., B.D.J. Batt, P.J. Caldwell, J.A. Kadlec and A.G. van der Valk. 2000a. Introduction to the Marsh Ecology Research Program. In Prairie Wetland Ecology: The Contribution of the Marsh Ecology Research Program. (Eds) H.R. Murkin, A.G. van der Valk and W.R. Clark. pp. 3-15. Ames: Iowa State University Press.

Resulting Publications on MERP Hydrology data:
Kadlec, J.A. 1983. Water budgets for small diked marshes. Water Resources Bulletin 19: 223-229.
Kadlec, J.A. 1993. Effects of depth of flooding on summer water budgets for small diked marshes. Wetlands 13: 1-9.