* Estimating
the effect of cropland to prairie conversion on peak storm runoff
* Effect
of geochemical processes on selenium in soil and water, central South
Dakota
* Groundwater
- surface water interaction
at Shingobee Lake, Minnesota
* Modeling groundwater recharge - discharge across the landscape
* Research watershed within The Nature Conservancy's Glacial
Ridge Project
* Hydrological
dynamics of wetlands
in the upper Turtle River watershed
* Hydrology
and geochemistry of springs and seeps at Pigeon Point, North Dakota
Changes to peak runoff resulting from
conversion of
cropland to prairie (Journal of Restoration Ecology)
Much of the original U.S. grassland has undergone
conversion to cropland. During the last few years large first- and
second-order watershed scale projects have begun to restore the native
cover and associated biodiversity in the tallgrass prairie ecoregion.
The effect on watershed hydrological budget is largely unknown,
especially concerning storm runoff. Curve numbers and their variability
are used here to estimate the uncertainty of peak runoff following the
change in land cover, given rainfall recurrence and the size of the
watershed. The method involves three steps: (1) estimate the time of
concentration for a large number of similar sized watersheds in the
region, (2) define the probability distribution for time of
concentration, curve numbers, and watershed area, (3) with these data,
generate input variables for a Monte Carlo analysis, which can then be
used to predict the mean and confidence interval of runoff. As an
example, spatial and hydrological characteristics of first- and
second-order watersheds ranging from 2 to 5 km² in the Red River
of the
North basin provide a log normal probability distribution for time of
concentration. Using the range of watershed area and a β-probability
distribution for curve number uncertainty, Monte Carlo analysis
predicts the change in peak runoff from an ensemble of watershed
realizations that characterize cropland to grassland conversion.
Results suggest that given 5- and 25-year, 24-hour rainfall recurrence,
peak runoff will be reduced by about 40 to 55%, with a large range of
uncertainty.
Selenium in soils of central South Dakota (abstract of paper to be submitted to Science of the Total Environment, with co-authors Md. Salah U. Sharif, Scott F. Korom, and John W. Finley)
Selenium is essential in the human diet, but has a low threshold for toxic concentration. Therefore, managing agriculture for optimal Se in grain crops and forage requires an understanding of the distribution and mobility of Se. Elevated concentration of Se occurs in waters, soils, forage, and near Milesville, central South Dakota, U.S.A. The research site lies in an elevated, dissected plain where soils developed on gently dipping Pierre Shale. Soils were sampled along catena transects and waters collected from soil, ponds, and shallow borings in areas of known elevated forage and crop Se. Both total and water-soluble soil extracts were analyzed. Saturated paste extracts consistently have a greater Se concentration than hot water extracts. Selenate is the dominant Se species; selenite was below detection in all samples. On average, 98% of soil Se is not water-soluble. Correlation between Se and phosphate and total iron suggests competition for adsorption sites. Ca correlates to total Se, but not water-soluble Se in soils or Se in waters. Total Se shows no correlation to Na and total S in the soils. Water-soluble Se in soils and dissolved Se in surface water and groundwater, however, correlate directly to Na, Mg, and sulfate concentration, suggesting that evaporitic Na- Mg-sulfate minerals may temporarily concentrate water-soluble Se in shallow soils. The dissolution and precipitation of these sulfates together with pH and Eh apparently control water-soluble Se distribution and mobilization. Our results indicate that the distribution of total Se shows much less spatial variation than water-soluble Se in the areas sampled. Characterizing the spatial distribution of labile Se will generally require detailed soil and landscape mapping.poster
presentation at the Soil Science Society Annual Meeting
Effects of Small-Scale Hydraulic Variation on Groundwater Discharge to Shingobee Lake, Minnesota (published in Hydrological Processes v. 16, p. 1921-1934 with co-author Hans Kishel)
Groundwater discharge often contributes to the water budget of a lake, but small-scale heterogeneities and large changes in hydraulic gradient over short distances generally make this component difficult to estimate. A 170 m2 grid within an area of springs and seeps along the shore of Shingobee Lake, Minnesota, was intensively instrumented to characterize groundwater-lake interaction in the sandy glacial sediments and organic rich sediments. Seepage meters in the lake and piezometer nests, installed at depths of 0.5 and 1.0 m below the ground surface and lakebed, were used to estimate groundwater flow. Statistical analysis of hydraulic conductivity estimated from slug tests indicated a range from 21 to 4.8x10-3 m day-1 and small spatial correlation. Although hydraulic gradients are overall upward and toward the lake, surface water that flows onto an area about two m onshore results in downward flow and localized recharge. Most flow occurred through more permeable conduits within three meters of the shore. Seepage meter and Darcy Law estimates of groundwater discharge agreed well within error limits. In the small area examined, discharge decreases irregularly with distance into the lake, indicating that sediment heterogeneity plays an important role in the distribution of groundwater discharge. Temperature gradients showed some relationship to discharge, but neither temperature profiles nor specific electrical conductance could provide a more convenient method to map groundwater-lake interaction. These results suggest that choosing a management option for spring-fed lakes requires site-specific data.
In September 2000, the Minnesota Chapter of The
Nature Conservancy (TNC) purchased over 22,000 acres in central
Polk
County, Minnesota, most in Tilden Township (Fig.
1). Additionally, several thousand acres contiguous to this
purchase
are owned and managed by TNC, the U.S. Fish and Wildlife Service, and
the
State of Minnesota. The area straddles ancient beach ridges on the
eastern
shore of glacial Lake Agassiz (Fig.
2).
Wetland drainage, farming, ranching, and aggregate mining during
the last 120 years have extensively altered this original tallgrass
prairie.
TNC, the USDA Natral Resources Conservation Service, and the U.S. Fish
and Wildlife Service are reconstructing the pre-settlement wetland and
upland environment
of the Glacial Ridge site, making it one of the largest ever prairie
restoration projects in the
U.S.. This research proposal outlines the concepts,
available resources, and short-term needs for establishing a research
and
educational watershed within the project site. (more
information)
Host - parasite / pathogen interaction on a spatially heterogeneous and temporally dynamic landscape: Hydrological modeling of grassland wetland linkages in natural and human-dominated landscapes (with graduate students Mike Davis, anticipated M.S. 2006 and Chris Laveau, M.S. 2004)
Objectives of the proposed study:
The goal of this research component will be to provide a conceptual
framework and model that describes the spatial and temporal variation
of
hydrologic features at Newman's amphibian study site in eastern Nelson
County, North Dakota. Ideally, this characterization should extend
throughout
the watershed in which the study site lies. Watersheds provide a
fundamental
spatial unit in which to (1) estimate groundwater and surface water
budget,
(2) relate all surface water channels, sub-basins, and their
interconnection,
and (3) recognize the relationship of soil catena to geomorphology,
hydrology,
and land use. Because of the irregular and subdued topography, it is
difficult
to define the extent of watersheds in the prairie pothole region.
Initially,
we will focus our effort on a watershed that fully contains the
amphibian
study area, based on the 30-m digital elevation model (DEM).
Objectives and Methods:
(1) Use existing data to map the surficial geology of the area.
(2) Make a spring and fall inventory of electrical conductivity and pH of wetlands, lakes, and ponds in the watershed study area, and, if possible, establish a correlation to the classification (Cowardin and others, 1979) used in the U.S. Fish and Wildlife Service National Wetland Inventory.
(3) Identify greater-than-annual periodicities in the precipitation record, if any exist, by computing autocorrelation for precipitation recorded for nearby weather stations. Precipitation constitutes the largest input to the prairie pothole water budget, and is therefore the best component to use.
(4) If greater-than-annual periodicities exist, then cross-correlation techniques (Davis, 1986) will be used to characterize the relationship between precipitation and the extent of wetlands. (Work completed by UND’s Geography will be used to quantify the temporal and spatial changes in wetland and open-water extent).
(5) Modify and apply a water budget method to model the effect of climate variability on the expansion and contraction of wetlands. Wigley and Jones (1986) used time interval, stream flow, precipitation, and potential evapotranspiration parameters to model changes in stream and river discharge; these methods may also work with wetland dynamics.
(6) Using the groundwater - surface model of Gerla (1999), map the distribution of recharge and discharge areas in the watershed study area. Soils maps of the area, recently digitized by Chris, will be used to corroborate the results.
Relationship of the component to the priorities of the research
group:
Landscape structure and the hydrological dynamics of the prairie upland
- wetland system play an important role in the evolution and demography
of pathogens/parasites and their vertebrate hosts. This relationship
couples
closely to the large climate variability that occurs in the
mid-continental
region.
latest
presentation that summarizes the work (ppt)
Hydrology and geochemistry of springs
and seeps at Pigeon Point, North Dakota
Recent work completed by Corey Askin (MS, 2004) at Pigeon Point
defined the water budget at this unique series of springs and seeps
along the Sheyenne River in southeastern North Dakota.
Owned and managed as a nature preserve by The Nature Conservancy,
the fens and wetlands host boreal plant species that occur far to the
northeast in Minnesota. The cold mineralized groundwater and
north-facing slope of the wetlands creates a unique ecological niche in
the otherwise droughty dunes of the Sheyenne delta. The diagram
below shows the water budget estimated by Corey.
Bill Lenarz is now exploring the how land cover affects infiltration
and groundwater processes, which influence the composition of water
discharged at the springs. His work will be completed as an MS degree
in late 2006.
