Simulated groundwater flow in the Ogallala and Arikaree aquifers, Rosebud Indian Reservation area, South Dakota – Revisions with data through water year 2008 and simulations of potential future scenarios

Abstract

B a se fr o m U .S . G e o lo g ic a l S u rv e y d ig it a l d a ta 1 :1 0 0 ,0 0 0 , 1 9 8 0 , 1 9 8 2 , 1 9 8 3 , 1 9 8 5 U n iv e rs a l T ra n sv e rs e M e rc a to r p ro je c ti o n , z o n e 1 4 T. 101 N.T. 100 N.T. 98 N.T. 97 N.T. 96 N.T. 95 N. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted materials contained within this report. Suggested citation:Long Horizontal coordinate information is referenced to the North American Datum of 1927 (NAD 27).Altitude, as used in this report, refers to distance above the vertical datum.Water year is the 12-month period, October 1 through September 30, and is designated by the calendar year in which it ends. The well number consists of the township number, followed by "N," the range number followed by "W," and the section number followed by a maximum of four uppercase letters that indicate, respectively, the 160-, 40-, 10-, and 2 1/2-acre tract in which the well is located. These letters are assigned in a counterclockwise direction beginning with "A" in the northeast quarter. A serial number following the last letter is used to distinguish between wells in the same 2 1/2-acre tract. Well-Numbering System AbstractThe Ogallala and Arikaree aquifers are important water resources in the Rosebud Indian Reservation area and are used extensively for irrigation, municipal, and domestic water supplies. Drought or increased withdrawals from the Ogallala and Arikaree aquifers in the Rosebud Indian Reservation area have the potential to affect water levels in these aquifers. This report documents revisions and recalibration of a previously published three-dimensional, numerical groundwater-flow model for this area. Data for a 30-year period (water years 1979 through 2008) were used in steady-state and transient numerical simulations of groundwater flow. In the revised model, revisions include (1) extension of the transient calibration period by 10 years, (2) the use of inverse modeling for steady-state calibration, (3) model calibration to base flow for an additional four surface-water drainage basins, (4) improved estimation of transient aquifer recharge, (5) improved delineation of vegetation types, and (6) reduced cell size near large capacity water-supply wells. In addition, potential future scenarios were simulated to assess the potential effects of drought and increased groundwater withdrawals.The model comprised two layers: the upper layer represented the Ogallala aquifer and the lower layer represented the Arikaree aquifer. The model's grid had 168 rows and 202 columns, most of which were 1,640 feet (500 meters) wide, with narrower rows and columns near large watersupply wells. Recharge to the Ogallala and Arikaree aquifers occurs from precipitation on the outcrop areas. The average recharge rates used for the steady-state simulation were 2.91 and 1.45 i...

Conceptual and numerical models of groundwater flow in the Ogallala and Arikaree aquifers, Pine Ridge Indian Reservation area, South Dakota, water years 1980-2009

“…Evapotranspiration decreases with the depth of the water level below land surface and is negligible when the depth to the water table is below the root zone (Long and Putnam, 2010). Generally, the depth of this root zone is assumed to be about 7 to 20 ft with the deeper root penetration (as much as 20 ft) associated with pine and deciduous forests.…”

“…Mean recharge rates of 2.91 in/yr for the Ogallala aquifer (or 15 percent of mean precipitation) and 1.45 in/yr for the Arikaree aquifer (or 7 percent of mean precipitation) were estimated after recalibration of the steady-state simulation of the model by Long and others (2003) using additional hydrologic data and enhanced parameter estimation techniques (Long and Putnam, 2010).…”

“…Precipitation data from station 395281 (Martin) were used for recharge zone 1 (Ogallala aquifer), station 394983 (Long Valley) was used for recharge zone 2 (eastern part of the Arikaree aquifer), and station 396736 (Porcupine 11N) was used for recharge zone 3 (western part of the Arikaree aquifer; table 4). Mean recharge for WYs 1980-2009 for the Ogallala and Arikaree aquifers was estimated as 15 and 7.5 percent of mean annual precipitation, respectively, determined based on the calibrated recharge values, expressed as a percentage of precipitation, from the model of the adjacent Rosebud Indian Reservation area (Long and Putnam, 2010).…”

“…Kolm and Case (1983) This model simulated groundwater flow of the Ogallala and Arikaree aquifers with a much smaller grid spacing compared to the model produced by Kolm and Case (1983). Long and Putnam (2010) updated the model developed by Long and others (2003) with additional data and simulations of hypothetical drought and increased groundwater withdrawal. Davis and Putnam (2013) developed conceptual and numerical models of groundwater flow for the Ogallala aquifer in Gregory and Tripp Counties, which are located east of Mellette and Todd Counties.…”

“…The first scenario represented an increase in groundwater withdrawals from 50 hypothetical production wells, and the second scenario represented a potential 30-year period of decreased recharge (drought). Kolm and Case (1983), Long and others (2003), Long and Putnam (2010), and Davis and Putnam (2013) previously developed groundwater models of the High Plains aquifer near the study area. Kolm and Case (1983) This model simulated groundwater flow of the Ogallala and Arikaree aquifers with a much smaller grid spacing compared to the model produced by Kolm and Case (1983).…”