NSERC CRD DROUGHT PROJECT

Goals and Objectives of Research

1) What were the spatial and temporal patterns of lake level and water availability within the Winnipeg River Drainage Basin over the past ~2000 years?

2) Are periods of low lake levels coherent among lakes within each of the southern and northern regions? (i.e., analysis of within region variability)

3) Are periods of low lake levels coherent between the southern and northern watersheds? (i.e., analysis of between region variability)

4) What implications do these findings have on future water resources in the WRDB?

Research design:

1) At least six lakes in the WRDB will be selected for detailed analysis of the sedimentary record to estimate past extremes in water availability, with an emphasis on detecting the low periods. Details of lake selection can be seen in CRD Annual Report (link CRD annual report). At least three lakes will be selected within the southern sub-watersheds of Winnipeg River and Lake of the Woods and at least three lakes from the northern sub-watersheds of English River and Lac Seul. (see map of Winnipeg River Drainage Basin).

2) Lake sediment surface sample collection and analysis will be carried out on each of the selected lakes (see field work in Study Lakes). Detailed bathymetric profiles will be developed and surface samples will be collected along multiple transects and analyzed for organic matter, chrysophyte scales and diatoms. The ecotonal boundaries of the planktonic versus benthic diatoms for each of the lakes will be used to determine the most sensitive coring site. The proportion of chrysophyte scales to diatoms can also be used as an indicator of the ecotonal boundary between the littoral (shallow near-shore) and pelagic (deeper central) lake zones. In addition, changes in percent organic matter (OM) content in sediments can be used to indicate changes in the boundary between the littoral and pelagic zone (see Background forTechniques for estimating past lake levels in drainage lakes).

3) Seismic profiling (High-resolution acoustic reflection) data will be collected on these lakes to acquire information about the thickness and distribution of sediments in the selected lakes (see Field Trip # 2 Reportsee Field Trip # 2 Report). These data are important to determine the sampling locations that can provide high-resolution sediment records in near-shore environs within each lake.  Lake sediment cores will be collected in appropriate near-shore environments based on the analysis of diatoms and other proxies in the surface samples, and the seismic profiles. Core location will be chosen to maximize the detection of declines in water level.

4) The cores will be analyzed for multiple indicators including diatoms, proportion of chrysophyte scales to diatoms, and percent organic matter. Lake specific transfer functions will be developed to identify the depth of the current pelagic/littoral transition using diatoms, chrysophytes, organic matter and possibly other indicators. A diatom-based depth model will be used to quantitatively estimate changes in lake level. This information, along with bathymetry and volume estimates, will be used to estimate declines in lake volume.

5) Dating of the cores will be based on analyses of 210Pb and 137Cs analyses for the recent sediments. Chronology for older samples will be estimated from AMS 14C dates on terrestrial carbon (e.g., needles, leaves, concentrated pollen samples).

6) Estimates of lake level, along with our previous record from ELA Lake 239, will be used to provide estimates of variations and coherency in surface waters within and between each of the watershed regions (e.g., % changes in lake level and lake volume).