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Research about Twin Cities Metropolitan Area

Source-linked reports with geographic coverage including Twin Cities Metropolitan Area.

10 recordsLinked to original sources
USGS2016

Water levels and groundwater and surface-water exchanges in lakes of the northeast Twin Cities Metropolitan Area, Minnesota, 2002 through 2015

Overview This study assessed lake-water levels and regional and local groundwater and surface-water exchanges near northeast Twin Cities Metropolitan Area lakes applying three approaches: statistical analysis, field study, and groundwater-flow modeling. Statistical analyses of lake levels were completed to assess the effect of physical setting and climate on lake-level fluctuations of selected lakes. A field study of groundwater and surface-water interactions in selected lakes was completed to (1) estimate potential percentages of surface-water contributions to well water across the northeast Twin Cities Metropolitan Area, (2) estimate general ages for waters extracted from the wells, and (3) assess groundwater inflow to lakes and lake-water outflow to aquifers downgradient from White Bear Lake. Groundwater flow was simulated using a steady-state, groundwater-flow model to assess regional groundwater and surface-water exchanges and the effects of groundwater withdrawals, climate, and other factors on water levels of northeast Twin Cities Metropolitan Area lakes.

Minnesota↗
USGS2016

Statistical analysis of lake levels and field study of groundwater and surface-water exchanges in the northeast Twin Cities Metropolitan Area, Minnesota, 2002 through 2015: Chapter A of Water levels and groundwater and surface-water exchanges in lakes of the northeast Twin Cities Metropolitan Area, Minnesota, 2002 through 2015

Water levels declined from 2003 to 2011 in many lakes in Ramsey and Washington Counties in the northeast Twin Cities Metropolitan Area, Minnesota; however, water levels in other northeast Twin Cities Metropolitan Area lakes increased during the same period. Groundwater and surface-water exchanges can be important in determining lake levels where these exchanges are an important component of the water budget of a lake. An understanding of groundwater and surface-water exchanges in the northeast Twin Cities Metropolitan Area has been limited by the lack of hydrologic data. The U.S. Geological Survey, in cooperation with the Metropolitan Council and Minnesota Department of Health, completed a field and statistical study assessing lake-water levels and regional and local groundwater and surface-water exchanges near northeast Twin Cities Metropolitan Area lakes. This report documents the analysis of collected hydrologic, water-quality, and geophysical data; and existing hydrologic and geologic data to (1) assess the effect of physical setting and climate on lake-level fluctuations of selected lakes, (2) estimate potential percentages of surface-water contributions to well water across the northeast Twin Cities Metropolitan Area, (3) estimate general ages for waters extracted from the wells, and (4) assess groundwater inflow to lakes and lake-water outflow to aquifers downgradient from White Bear Lake. Statistical analyses of lake levels during short-term (2002–10) and long-term (1925–2014) periods were completed to help understand lake-level changes across the northeast Twin Cities Metropolitan Area. Comparison of 2002–10 lake levels to several landscape and geologic characteristics explained variability in lake-level changes for 96 northeast Twin Cities Metropolitan Area lakes. Application of several statistical methods determined that (1) closed-basin lakes (without an active outlet) had larger lake-level declines than flow-through lakes with an outlet; (2) closed-basin lake-level changes reflected groundwater-level changes in the Quaternary, Prairie du Chien, and Jordan aquifers; (3) the installation of outlet-control structures, such as culverts and weirs, resulted in smaller multiyear lake-level changes than lakes without outlet-control structures; (4) water levels in lakes primarily overlying Superior Lobe deposits were significantly more variable than lakes primarily overlying Des Moines Lobe deposits; (5) lake-level declines were larger with increasing mean lake-level elevation; and (6) the frequency of some of these characteristics varies by landscape position. Flow-through lakes and lakes with outlet-control structures were more common in watersheds with more than 50 percent urban development compared to watersheds with less than 50 percent urban development. A comparison of two 35-year periods during 1925–2014 revealed that variability of annual mean lake levels in flow-through lakes increased when annual precipitation totals were more variable, whereas variability of annual mean lake levels in closed-basin lakes had the opposite pattern, being more variable when annual precipitation totals were less variable. Oxygen-18/oxygen-16 and hydrogen-2/hydrogen-1 ratios for water samples from 40 wells indicated the well water was a mixture of surface water and groundwater in 31 wells, whereas ratios from water sampled from 9 other wells indicated that water from these wells receive no surface-water contribution. Of the 31 wells with a mixture of surface water and groundwater, 11 were downgradient from White Bear Lake, likely receiving water from deeper parts of the lake. Age dating of water samples from wells indicated that the age of water in the Prairie du Chien and Jordan aquifers can vary widely across the northeast Twin Cities Metropolitan Area. Estimated ages of recharge for 9 of the 40 wells sampled for chlorofluorocarbon concentrations ranged widely from the early 1940s to mid-1970s. The wide range in estimated ages of recharge may have resulted from the wide range in the open-interval lengths and depths for the wells. Results from stable isotope analyses of water samples, lake-sediment coring, continuous seismic-reflection profiling, and water-level and flow monitoring indicated that there is groundwater inflow from nearshore sites and lake-water outflow from deep-water sites in White Bear Lake. Continuous seismic-reflection profiling indicated that deep sections of White Bear, Pleasant, Turtle, and Big Marine Lakes have few trapped gases and little organic material, which indicates where groundwater and lake-water exchanges are more likely. Water-level differences between White Bear Lake and piezometer and seepage measurements in deep waters of the lake indicate that groundwater and lake-water exchange is happening in deep waters, predominantly downgradient from the lake and into the lake sediment. Seepage fluxes measured in the nearshore sites of White Bear Lake generally were higher than seepage fluxes measured in the deep-water sites, which indicates that groundwater-inflow rates at most of the nearshore sites are higher than lake-water outflow from the deep-water sites.

Minnesota↗
USGS1994

Characterization of ground-water discharge from bedrock aquifers to the Mississippi and Minnesota Rivers at three areas, Minneapolis-St. Paul area, Minnesota

The hydrogeology at three areas along the Mississippi and Minnesota Rivers in the Minneapolis-St. Paul area were studied to characterize ground-water discharge from bedrock aquifers to the two rivers. Along the Mississippi River between Fridley and Brooklyn Center, a buried valley underlying the Mississippi River cuts through the overlying terrace deposits and glacial-drift deposits into two underlying bedrock hydro- geologic units: the St Peter aquifer, and a rubble zone between the St. Peter and Prairie du Chien-Jordan aquifers. Shallow ground-water flow in the near-surface gray and upper red tills and sand and gravel outwash aquifer discharges to springs along the edge of the river. Ground water flowing through the rubble zone and upper part of the Prairie du Chien-Jordan aquifer probably discharges through alluvial deposits to the river. In study area 2, along the Minnesota River between Eagan and Bloomington, almost 200 feet of post-glacial alluvium, glaciofluvial sand and gravel, Pleistocene lake deposits, and peat fill a bedrock valley under the present-day Minnesota River. As much as 40 feet of post-glacial peat, silty clay, clay, and muck lie near the river-valley walls. Confining units beneath the river channel impede the discharge of ground water from the underlying Prairie du Chien-Jordan aquifer to the river. Ground water discharges to wetlands, lakes, and springs along both the north and south side of the river. Along the Mississippi River at Minneapolis about 5 miles upstream of the confluence of the Minnesota and Mississippi Rivers, the Mississippi River lies in a post-glacial valley cut through thin glacial drift into the St. Peter aquifer. Beneath the river, ground water flows from the St. Peter aquifer through the overlying post-glacial ailuvium to the Mississippi River. No confining unit separates the St. Peter aquifer and the river.

Minnesota↗
USGS1990

Effects of present and projected ground-water withdrawals on the Twin Cities aquifer system, Minnesota

The Twin Cities aquifer system in Minnesota contains 5 aquifers and 4 confining units composed of 14 stratigraphic units. Bedrock aquifers consist of friable sandstones and highly fractured carbonate rocks; aquifers in the glacial drift consist of outwash and alluvium. From 1880 to 1980, groundwater withdrawals had caused long-term declines of water levels of as much as 90 feet in the Prairie du Chien-Jordan aquifer and 240 feet in the deeper Mount Simon-Hinckley aquifer--the two major sources of ground-water supplies in the area. A steady-state model of ground-water flow was used successfully to simulate the potentiometric surfaces of the aquifers during the 1970's. assuming a withdrawal rate of about 190 million gallons per day from the entire system. Projected changes in population and industrial development suggest that future ground-water withdrawals may increase from those for the 1970's. Steady-state model results indicate that the potentiometric surface of the Mount Simon-Hinckley aquifer would be lowered as much as 400 feet if pumpage from that aquifer were increased by 125 percent above 1980 ground-water withdrawal rates of about 200 million gallons per day. The potentiometric surface of the Prairie du Chien-Jordan aquifer also would be lowered as much as 400 feet if pumpage from that aquifer were increased by 200 percent above 1980 ground-water withdrawals of 160 million gallons per day. Given the projected distribution of future ground-water development, and the limitations inherent in simulating ground-water flow, the model results indicate that an approximate limit of ground-water availability in the Twin Cities Metropolitan Area, Minnesota, is from about 500 to 800 million gallons per day.

Minnesota↗
USGS1984

Effects of an urban wetland on sediment and nutrient loads in runoff

An urban wetland in the Minneapolis-St. Paul Metropolitan Area was found to retain sediment and nutrient loads in runoff routed through the wetland. Sediment and nutrient loads in runoff were measured during 1982 at the inlet and outlet of the 6.4-bectare urban wetland. Comparison of annual loads entering and leaving the wetland showed that retention of incoming loads in the wetland was 97 percent of nonvolatile suspended solids, 76 percent of volatile suspended solids, 48 percent of total phosphorus, 4 percent of dissolved phosphorus, 3 percent of dissolved nitrite plus nitrate nitrogen, 1 percent of total ammonia nitrogen, and 47 percent of total organic nitrogen. Flow volume was increased on an annual average basis by 5 percent between the wetland inlet and oulet. Most retention of sediment and nutrient loads occurred between late April and mid-July. Retention of sediment and nutrient loads in the wetland was associated with sedimentation processes. Dissolved nutrients generally were not retained in the wetland because the residence time of water passing through was not long enough for removal by biological processes. Effectiveness of the wetland in retaining sediment and nutrient loads in runoff varies annually. Long-term and short-term impacts of the retention of sediment and nutrients in the wetland on wetland flora and fauna are unknown.

Minnesota↗
USGS1984

Water levels and water-level changes in the Prairie du Chien-Jordan and Mount Simon-Hinckley aquifers, Twin Cities metropolitan area, Minnesota, 1971-80

The ground-water system in the Twin Cities Metropolitan Area includes five aquifers; two of these aquifers the Prairie du Chien-Jordan and the Mount Simon-Hinckley supply about 80 percent and 10 percent, respectively, of the ground water pumped for public supply. Water levels and changes in water levels in these two aquifers differ greatly in the Twin Cities Metropolitan Area. The Mississippi, Minnesota, and St. Croix Rivers are in hydraulic connection with and influence the pattern of flow in the upper aquifer, the Prairie du Chien-Jordan. Water generally flows toward these streams from water-level highs northeast, northwest, and south of Minneapolis and St. Paul. Consequently, heavy pumping has caused only localized cones of depression in the potentiometric surface of this aquifer. In contrast, the Mount Simon-Hinckley, which has only a slight hydraulic connection to the streams, is greatly influenced by pumping. Pumping in the urban centers of Minneapolis and St. Paul has caused a large cone of depression in the Mount Simon-Hinckley potentiometric surface. During 1971, the measurable cone was centered in eastcentral Hennepin County, was about 25 miles in diameter, and was as much as 150 feet deep at its center. Between 1971 and 1980, average water levels in the Prairie du Chien-Jordan aquifer changed less than 5 feet in most of the study area, but rose or declined as much as 25 feet locally in response to pumpage and recharge. During this period, seasonal declines of water levels from winter to summer lessened, and the area where these declines exceeded 10 feet decreased. In contrast, between 1971 and 1980, average water levels in the Mount Simon-Hinckley aquifer rose as much as 60 feet in the center of the cone of depression in response to decreased pumping. Also, the measurable cone of depression contracted from about 25 miles to about 15 miles in diameter. However, because of increased summer pumping due to below-average precipitation during 1980, seasonal water levels declined much more and over a wider area during 1980 than in 1971. Water-level data suggest that (1) little variation in annual pumpage between 1971 and 1980 from the Prairie du Chien-Jordan aquifer produced generally stable water levels in that aquifer, (2) decreased annual pumpage from the Mount Simon-Hinckley aquifer from 1971 to 1980 caused water levels in that aquifer to rise, and (3) a greater seasonal component of pumpage from the Mount Simon-Hinckley aquifer than from the Prairie du Chien-Jordan produced larger and more widespread seasonal water-level declines in the Mount Simon-Hinckley than in the Prairie du Chien-Jordan, particularly during dry years.

Minnesota↗
USGS1984

Areal lithologic changes in bedrock aquifers in southeastern Minnesota as determined from natural-gamma borehole logs methods

Sedimentary rocks of Paleozoic age in the Hollandale embayment in southeastern Minnesota are as much as 2,000 feet thick and, with the underlying Hinckley sandstone of Proterozoic age, comprise the following five layered aquifers (beginning with the oldest): the Mount Simon-Hinckley, Ironton-Galesville, Prairie du Chien-Jordan, St. Peter and Upper Carbonate. Many of the Paleozoic formations show transitional facies changes from a deep marine depositional environment in the middle of the embayment to a near shore environment along the periphery. Borehole natural-gamma logs were collected to investigate the effects of regional lithologic changes on the hydrology of the Ironton-Galesville, Prairie du Chien-Jordan and St. Peter aquifers. Interpretation of natural-gamma logs shows that a fine-grained sandstone at the base of the Galesville sandstone (basal part of the Ironton-Galesville aquifer) thickens toward the central part of the embayment, which may account for the decrease in hydraulic conductivity of the Ironton-Galesville aquifer in that direction. The Jordan sandstone, which underlies the Prairie du Chien Group, consists of three members in southeastern Minnesota: the basal Norwalk member, a silty, fine-grained sandstone; the middle Van Oser member, a coarse- to medium-grained quartzose sandstone; and the upper Sunset Point member, a clayey dolomitic sandstone. The Norwalk and Van Oser members were identified by interpretation of natural-gamma logs. Hydraulic conductivity of the Prairie du Chien-Jordan aquifer generally is highest in the Twin City basin (50 feet per day) where the Van Oser is the predominant member; it is lowest to the east and southeast (25 feet per day) where the Norwalk member thickens. Interpretation of natural-gamma logs indicates that the shaley and silty sandstones that comprise the basal St. Peter confining bed, which separates the St. Peter and Prairie du Chien aquifers, are as much as 80 feet thick in the Twin City basin, but are absent in the southern part of the embayment. Differences in potentiometric head across the basal St. Peter are about 30 feet in the Twin City basin where the confining bed is present but only 5 to 10 feet to the south where the confining bed is absent and where the St. Peter aquifer directly overlies the Prairie du Chien-Jordan aquifer.

Minnesota↗
USGS1975

Configuration of water table and distribution of downward leakage to the Prairie du Chien-Jordan Aquifer in the Minneapolis-Saint Paul metropolitan area, Minnesota

The configuration of the water table as plotted at a contour interval of 20 feet (6 metres) on quadrangle maps (scale 1:2,500) of the Minneapolis-Saint Paul metropolitan area. Control points used for mapping were water levels in wells, lakes and sloughs, and places where topographic contours cross perennial streams. A computer program, using a variation of Darcy's law, was developed to determine distribution of 1) downward leakage to the Prairie du Chien-Jordan aquifer under steady-state conditions, using estimated vertical-hydraulic conductivity values for overlying materials; 2) calculated vertical hydraulic conductivity values, assuming uniform leakage to the aquifer; and 3) additional leakage to the aquifer resulting from increased pumpage during the summer. For data determination and data input to the computer program, the area was gridded into units of 1-minute longitude by 1-minute latitude, about 600 acres (243 hectares) per unit. Previous work estimated the increased summer pumpage (1971) of ground water to be 127 million gallons (481x106 litres) per day. Calculations, made Within the limits of governing assumptions, indicate that 10 to 20 percent of increased summer pumpage is derived from increased leakage. Most of the remainder is probably from captured natural discharge and induced recharge from major streams within the influence of summer cones of depression. Based on available data and estimates of vertical hydraulic conductivity for geologic units, major leakage to the Prairie du Chien-Jordan aquifer is indicated to occur in formation subcrop areas, especially where these areas are. overlain by the most permeable glacial drift.

Minnesota↗