The Sac and Fox Tribe of the Mississippi in Iowa is the only federally recognized Tribe in the State of Iowa and is commonly known as the Meskwaki Nation. The Tribe owns more than 8,100 acres, referred to as the “Meskwaki Settlement.” The Meskwaki Settlement uses a well field that withdraws water from the Iowa River alluvial aquifer (IRAA) to supply drinking water to members of the Tribe. Increased severity and timing of flooding and drought conditions, coupled with water-quality concerns in the Iowa River, have prompted the Meskwaki Nation to start identifying tools to provide a better understanding of how extreme climate events (changes in streamflow, flood frequency, and magnitude and persistence of drought conditions), increasing water-supply demands, and groundwater storage depletion will affect water availability in the IRAA.
From June 2017 through September 2020, the U.S. Geological Survey, in cooperation with the Meskwaki Nation, collected continuous and discrete groundwater level data from 11 wells in a U.S. Geological Survey monitoring-well network. Groundwater level data collected at these wells were assessed with daily precipitation data and compared to changes in stream level elevations and daily groundwater withdrawals to determine how these changes affect groundwater-table elevations. Results from this study could be used to guide the development of a conceptual model for groundwater flow and a groundwater flow model for the IRAA to quantify and forecast the effect of groundwater withdrawals, Iowa River streamflow, and local precipitation on the water table in the IRAA.
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The authors would like to thank the Sac and Fox Tribe of the Mississippi in Iowa for funding the operation of and maintenance of the streamgaging station and groundwater wells used for this study.
Multiply | By | To obtain |
Length | ||
---|---|---|
inch (in.) | 2.54 | centimeter (cm) |
inch (in.) | 25.4 | millimeter (mm) |
foot (ft) | 0.3048 | meter (m) |
Area | ||
acre | 4,047 | square meter (m2) |
Flow rate | ||
gallon per day (gal/d) | 0.003785 | cubic meter per day (m3/d) |
Vertical coordinate information is referenced to the North American Vertical Datum of 1988 (NAVD 88).
Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD83).
Elevation, as used in this report, refers to distance above the vertical datum.
Iowa River alluvial aquifer
Meskwaki Nation Department of Natural Resources
National Oceanic and Atmospheric Administration
U.S. Geological Survey
The Sac and Fox Tribe of the Mississippi in Iowa is the only federally recognized Tribe in the State of Iowa and is commonly known as the Meskwaki Nation. The Tribe owns more than 8,100 acres, referred to as the “Meskwaki Settlement.” The Meskwaki Settlement well field (hereafter referred to as the “well field”) source water primarily comes from the Iowa River alluvial aquifer (IRAA) in Tama County, Iowa (
Geographic area, local infrastructure, landscape features, and data collection sites near Tama, Iowa, 2017–20.
From June 2017 through September 2020, the U.S. Geological Survey (USGS), in cooperation with The Meskwaki Nation, collected continuous and discrete groundwater level data from 11 wells in a USGS monitoring-well network. Groundwater level data collected in these wells were assessed with daily precipitation data, stream level elevations on the Iowa River (hereafter referred to as “stage”), and daily groundwater withdrawals to determine how variability in these properties affects groundwater-table elevations in the unconfined IRAA near the well field (hereafter referred to as “water table”). Results from this study can be used as the first step in developing a conceptual model for groundwater flow and a groundwater flow model for the IRAA. The groundwater model could be used to quantify and forecast the effects of local precipitation, stage on the Iowa River, and groundwater withdrawals on the water table in the IRAA.
The purpose of this report is to characterize the hydrodynamics of the IRAA around the well field using daily mean groundwater elevation data, daily mean groundwater withdrawal data, precipitation data, and stage data, collected near Tama, Iowa, from June 30, 2017, to September 30, 2020.
The study area is the IRAA around a well field that is west of the city of Tama, Iowa. The IRAA is a surficial, unconfined aquifer generally composed of 40–50 feet (ft) of alluvial sand and gravel deposits in the study area that overlie glacial till (
To better understand how changes in stage on the Iowa River and adjacent well field operations affect water-table elevations in the IRAA, continuous (one reading every 15 minutes) groundwater level (wells 2A–12A and 6B) and stage data (Iowa River) were collected by the USGS in the IRAA and on the Iowa River (
[USGS, U.S. Geological Survey; NAD83, North American Datum of 1983; NAVD 88, North American Vertical Datum of 1988; °, degree; ', minute; ″, second; IA, Iowa; --, no data or not applicable]
USGS site number | Station name | Field identifier | Latitude |
Longitude |
Year established | Land surface elevation, in feet above NAVD 88 | Well depth, in feet |
415935092401401 | 083N16W23AAAB 2011MMW–2A | 2A | 41°59'35″ | 92°40'14″ | 2011 | 837.79 | 39.0 |
415944092395401 | 083N16W13CCAD 2011MMW–3A | 3A | 41°59'44″ | 92°39'54″ | 2011 | 835.17 | 42.4 |
415856092392001 | 083N16W24DBDD 2011MMW–4A | 4A | 41°58'56″ | 92°39'20″ | 2011 | 830.41 | 39.5 |
415908092401901 | 083N16W23DABA 2011MMW–5A | 5A | 41°59'08″ | 92°40'19″ | 2011 | 831.85 | 32.5 |
415806092394501 | 083N16W25CACD 2011MMW–6A | 16A | 41°58'46.2″ | 92°39'46″ | 2011 | 828.28 | 17.0 |
415806092394502 | 083N16W25CACD 2019MMW–6B | 6B | 41°58'46.2″ | 92°39'46″ | 2019 | 828.28 | 17.0 |
415855092394701 | 083N16W24CDBB 2011MMW–7A | 7A | 41°58'55″ | 92°39'47″ | 2011 | 826.77 | 38.0 |
415855092393501 | 083N16W24CDAA 2011MMW–8A | 8A | 41°58'55″ | 92°39'35″ | 2011 | 826.83 | 35.0 |
415906092392001 | 083N16W24DBAA 2011MMW–9A | 9A | 41°59'06″ | 92°39'20″ | 2011 | 841.50 | 42.5 |
415924092393701 | 083N16W24BADD 2011MMW–11A | 11A | 41°59'24″ | 92°39'37″ | 2011 | 829.69 | 41.7 |
415911092395601 | 083N16W24BCDC 2011MMW–12A | 12A | 41°59'11″ | 92°39'56″ | 2011 | 828.25 | 40.0 |
05451770 | Iowa River at County Highway E49 near Tama, Iowa | Iowa River | 41°57'51.32″ | 92°38'11.58″ | 2011 | 810.47 | -- |
Well found destroyed on December 3, 2019, and replaced with 6B.
Beginning on June 30, 2017, continuous groundwater elevation data were collected in six monitoring wells (4A, 7A, 8A, 9A, 11A, 12A) near the well field. In the summer of 2019, the monitoring effort was expanded to include an additional four wells (2A, 3A, 5A, 6A) and in winter of 2020 monitoring began in a newly established well (6B) (
From June 2017 through September 2020, continuous stage data on the Iowa River at County Highway E49 near Tama, Iowa (USGS streamgaging station 05451770), were collected following methods established by USGS for the collection of stage measurements (
A water-table elevation map is a contour map of the water table interpolated from observed water levels, and in this study, surface water body elevations, observed water levels, and several hydrogeologic assumptions were used to interpolate contour line placement. A total of 17 surface water body elevations were extracted from a digital elevation model (
Water-table elevations typical of drought/low flow conditions for the Iowa River alluvial aquifer near Tama, Iowa, as represented by September 2017 elevations.
To assess how stage on the Iowa River, local precipitation, and operation of the well field affect observed elevations of the groundwater table, three periods of data were selected for analysis. One period was selected to exemplify the effect of sustained low stage on the Iowa River on water-table elevation (July 1 to September 30, 2020), one period was selected to exemplify the effect of sustained high stage on the Iowa River on water-table elevations (September 1 to November 30, 2018), and one period was selected as an example of variable stage from localized precipitation events versus upstream flows (February 10 to July 10, 2020). Daily groundwater withdrawals and precipitation are variable throughout each of these periods. A reference line of 250,000 gallons per day was applied to the daily groundwater withdrawal data provided by the MNDNR and indicated typical withdrawals from the IRAA. Actual daily groundwater withdrawal volumes were put on a relative scale from 0 to 1 to illustrate deviation from typical withdrawal volume.
The hydrologic setting of the study area includes groundwater and surface water interaction, topography, surficial geology, well field operations, and climate. The water-table map created for the study area provides a typical surface of the water table for low-flow/drought conditions observed in September 2017. In general, high hydraulic gradients are observed near the upland margin, and low gradients are associated with the valley floor (
To better characterize the water-table changes compared to stage on the Iowa River, groundwater withdrawals, daily mean groundwater elevation data, and local precipitation were analyzed. Three periods of data were used to illustrate and assess changes to the water table related to sustained low stage, sustained high stage, and variable stage. For each period, all the available groundwater data for that period were used and the associated figures were generally organized so the wells with the highest water-table elevations were at the top and descended to the Iowa River stage, which is at the bottom. This is consistent with the presumed typical direction of groundwater flow and the water-table elevation map (
To examine the effect of sustained low stage on water-table elevations, a period of hydrologic data from July 1 to September 30, 2020, was analyzed to determine how low stage on the Iowa River, groundwater withdrawals, and precipitation affect water-table elevations (
Daily mean water-table elevations, relative groundwater withdrawals, and precipitation, July 1 to September 30, 2020.
The water table during this period is consistent with the water-table elevation map and indicates groundwater flows in the south to southeasterly direction with a cone of depression around the well field (
To better characterize how higher stage affects water-table elevations in the well field, a period from September 1 to November 30, 2018, was analyzed to determine how high stage on the Iowa River, groundwater withdrawals, and precipitation affect water-table elevations (
Daily mean water-table elevations, relative groundwater withdrawals, and precipitation, September 1 to November 20, 2018.
Generally, convergence is observed in the water level elevations among the monitoring wells when there is abundant local precipitation and stage on the Iowa River is high. During the first peak, well 8A seemed to have been overtopped, which may have damaged the integrated pressure sensor; it stopped working after the recession and before the next more sustained event(s) (
During peak water level, river stage was slightly higher than the observed water-table elevations in well 9A, which is the closest monitoring well to the well field and was used throughout this study as a general indicator of extent of the cone of depression (
To gain insight into how a period of variable stage on the Iowa River affects groundwater elevations in the IRAA, a 5-month period of data from February 10 to July 10, 2020, was analyzed to determine how variable stage on the Iowa River, groundwater withdrawals, and precipitation affect water-table elevations (
Daily mean water-table elevations, relative groundwater withdrawals, and precipitation, February 10 to July 10, 2020.
In mid-March 2020, there was a multiday rainfall event when 1.24 in. of precipitation was recorded from March 18 to 20 (
Two additional peak high stages were observed in June 2020 but were much more affected by local precipitation and drainage (
The Sac and Fox Tribe of the Mississippi in Iowa is the only federally recognized Tribe in the State of Iowa and is commonly known as the Meskwaki Nation. The Tribe owns more than 8,100 acres, referred to as the “Meskwaki Settlement.” The Meskwaki Settlement uses a well field that withdraws water from the Iowa River alluvial aquifer (IRAA) to supply drinking water to members of the Tribe. Increased severity and timing of flooding and drought conditions, coupled with water-quality concerns in the Iowa River, have prompted the Meskwaki Nation to start identifying tools to provide a better understanding of how extreme climate events (changes in streamflow, flood frequency, and magnitude and persistence of drought conditions), increasing water-supply demands, and groundwater storage depletion will affect water availability in the IRAA.
From June 2017 through September 2020, the U.S. Geological Survey in cooperation with the Meskwaki Nation, collected continuous and discrete groundwater level data from 11 wells in a U.S. Geological Survey monitoring-well network. Groundwater level data collected at these wells were assessed with daily precipitation data and compared to changes in stream level (stage) elevations and daily groundwater withdrawals to determine how these changes affect groundwater-table elevations. Results from this study could be used to guide the development of a conceptual model for groundwater flow and a groundwater flow model for the IRAA to be used to quantify and forecast the effect of Iowa River streamflow, groundwater withdrawals, and local precipitation on the water table in the IRAA.
Three periods of data were used to demonstrate how the water table changes in relation to stage on the Iowa River, well field operations, and local precipitation. A low-stage period from July 1 to September 30, 2020, indicated that the water table is generally flowing in the downstream direction and the effects of well field operations on the water table are more apparent. Inputs from precipitation during dry periods indicate infiltration to the IRAA. A high-stage period from September 1 to November 30, 2018, indicated that during periods of high stage and abundant local precipitation, water is flowing into the well field area from the uplands and from the Iowa River. During high stage on the Iowa River, water-table elevations are all similar across the floodplain, but as the river recedes, the water-table elevations begin to diverge again. Well field operations in late October and mid-November 2018 were not observed to cause much of an effect on groundwater elevations within the IRAA. A period with variable stage from February 10 to July 10, 2020, indicated that the water table can respond differently depending on whether high stage on the Iowa River is the result of upstream flows or localized precipitation events. The railroad can impound water and promote recharge to the well field during local precipitation events, whereas during upstream flow events, it can restrict water from entering the well field. Qualitative groundwater modeling coupled with the flood-inundation model could help to better quantify and demonstrate how water is moving in the floodplain with respect to well field operations and stage on the Iowa River.
For more information about this publication, contact:
Director, USGS Central Midwest Water Science Center
400 South Clinton Street, Suite 269
Iowa City, IA 52240
319–337–4191
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