High Plains Aquifer (HPA)

High Plains Aquifer (HPA)

The High Plains aquifer (HPA) in the Great Plains physiographic province underlies about 450,000 km2 in parts of eight States (Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming) of the U.S. In 2000, the High Plains aquifer had an estimated  3.67 x 1012 cubic meters (m3) of drainable water in storage, making it one of the largest aquifers in the world (McGuire, 2007). Elevations of the High Plains range from about 300 m along the eastern boundary to about 2,400 meters (m) along the north-western boundary (McMahon et al. 2007).  The topography is characterized by flat to gently rolling terrain.

The High Plains has a middle-latitude, semi-arid continental climate (average annual air temperature ranges from 4 to 18°C), characterized by abundant sunshine, moderate average annual precipitation (30 to 84 cm), frequent winds, low humidity, and a high rate of annual evaporation (152 to 277 cm) (Dennehy et al. 2002).  The large areal extent of the High Plains results in relatively large north-to-south temperature gradients (cooler in the north and warmer in the south) and east-to-west precipitation gradients (more precipitation in the east and less precipitation in the west).

The population of the study area in 2000 was approximately 2.3 million people. The majority (77%) of this population reside in rural areas and smaller towns and cities, while only 23% live in the four largest cities: Lubbock, Texas (199,564), Amarillo, Texas (173,627), Midland, Texas (94,996), and Cheyenne, Wyoming (53,011) (McMahon et al. 2007) (Fig. 1). The dominant land use/land cover is rangeland (about 56%) and agriculture (about 38%, in cultivated crops, small grains, fallow, and pasture/hay); urban land use accounts for only 3% (McMahon et al. 2007).  About one-third of the agricultural land is irrigated, mostly concentrated in eastern Nebraska, south-western Kansas, and the west-central part of the Texas Panhandle (McMahon et al. 2007).

Use of groundwater from the High Plains aquifer as a source of irrigation water has transformed the study area into one of largest and most productive agricultural regions, earning it the nickname “breadbasket of the world” (Opie 2000). Groundwater withdrawals from the High Plains aquifer in the year 2000 accounted for about 20% of total groundwater withdrawn in the U.S. (Maupin and Barber 2005). Most (97%) of the water withdrawn from the High Plains aquifer is used for irrigation (Maupin and Barber 2005).  Although withdrawals for drinking water account for a relatively small percentage of the total groundwater use, they provide drinking water for about 82% of the 2.3 million people who live within the study area boundary (McMahon et al. 2007).

The High Plains aquifer consists of sedimentary deposits that form six hydraulically connected hydrogeologic units. The most extensive of these hydrogeologic units is the Ogallala Formation, which makes up about three-fourths of the total High Plains study area (McMahon et al. 2007). The depth to water below land surface (unsaturated-zone thickness) ranges from 0 to approximately 152 m, averages about 30.5 m, and is generally greatest in the central and southern High Plains (McMahon et al. 2007).  The saturated thickness of the High Plains aquifer ranges from less than 1 to more than 300 m and averages about 61 m (McMahon et al. 2007). The saturated thickness varies geographically and is greatest in the northern High Plains.

Evaporation rates exceed precipitation rates across much of the High Plains, so little water is available to recharge the aquifer. Recharge to the High Plains aquifer occurs by infiltration of irrigation water, aerially diffuse infiltration from precipitation, focused infiltration of storm- and irrigation-water runoff through streambeds and other topographic depressions (Gurdak et al. 2008), and upward movement of water from underlying aquifers (McMahon et al. 2007). Discharge from the High Plains aquifer is primarily to irrigation well pumping, streams and underlying aquifers, groundwater flow across the eastern boundary of the aquifer, and evapotranspiration. Regional groundwater flow is generally from west to east; however, local variability in hydraulic gradients can result in different directions of groundwater flow, particularly near high-capacity pumping wells and major rivers.

Water levels have declined substantially since predevelopment times (approximately the mid-1950s) because groundwater withdrawals have greatly exceeded recharge across much of the aquifer (McGuire et al. 2003). The largest water-level declines range from 15 to more than 45 m, primarily across parts of Kansas, Oklahoma, New Mexico, and Texas. The saturated thickness of the aquifer has decreased by more than 50% in some parts of Kansas and Texas (McGuire 2007). This groundwater depletion has led to increased pumping costs and a reduction of water discharging to streams, among other things. Ecosystems along riparian corridors that rely on groundwater discharge are adversely affected by even small volume changes in the groundwater system (Alley 2006).

To learn more contact:

Dr. Jason J. Gurdak, Assistant Professor, Department of Geosciences, Hydrogeology and Water Resources Research Group, San Francisco State University, San Francisco, California, United States of America. email: jgurdak@sfsu.edu

Example Publications (last 5 years):

Gurdak, J.J., McMahon, P.B., and Bruce, B.W., 2012, Vulnerability of groundwater quality to human activity and climate change and variability, High Plains aquifer, USA, pp. 145-167, In Treidel, H., Martin-Bordes, J.J., and Gurdak, J.J., (Eds.). Climate change effects on groundwater resources: A global synthesis of findings and recommendations, International Association of Hydrogeologists (IAH) – International Contributions to Hydrogeology, Taylor & Francis publishing, 414 p., ISBN 978-0415689366. http://www.crcpress.com/product/isbn/9780415689366

Gurdak, J.J., and Qi, S.L., 2012, Vulnerability of recently recharged groundwater in principal aquifers of the United States to nitrate contamination, Environmental Science and Technology 46(11): 6004-6012., doi:10.1021/es300688b.

Green, T., Taniguchi, M., Kooi, H., Gurdak, J.J., Hiscock, K., Allen, D., Treidel, H., and Aurelia, A., 2011, Beneath the surface of global change: Impacts of climate change on groundwater, Journal of Hydrology 405:532-560, doi:10.1016/j.jhydrol2011.05.002.

Gurdak. J.J., and Roe, C.D., 2010. Review: Recharge rates and chemistry beneath playas of the High Plains aquifer, USA, Hydrogeology Journal, v. 18, no. 18, 1747-1772, doi:10.1007/s10040-010-0672-3. 

Gurdak, J.J., Walvoord, M.A., and McMahon, P.B., (2008), Susceptibility to enhanced chemical migration from depression-focused preferential flow, High Plains aquifer, Vadose Zone Journal 7(4), 1172-1184, doi: 10.2136/vzj2007.0145.

Gurdak, J.J., 2008. Ground-water vulnerability: Nonpoint-source contamination, climate variability, and the High Plains aquifer, VDM Verlag Publishing, Saarbrucken, Germany, ISBN: 978-3-639-09427-5, 223 p.

Gurdak, J.J., Hanson, R.T., McMahon, P.B., Bruce, B.W., McCray, J.E., Thyne, G.D., and Reedy, R.C., (2007), Climate variability controls on unsaturated water and chemical movement, High Plains aquifer, United States, Vadose Zone Journal 6(2), 533-547, doi: 10.2136/vzj/2006.0087.

Gurdak, J.J., McCray, J.E., Thyne, G.D., and Qi, S.L., (2007), Latin-hypercube approach to estimate uncertainty in ground-water vulnerability, Ground Water, 45, 3, 348-361, doi: 10.1111/j.1745-6584.2006.00298.x.

Rajagopalan, S., Anderson, T.A., Fahlquist, L., Rainwater, K.A., Ridley, M., and Jackson, W.A. 2006, Widespread presence of naturally occurring perchlorate in High Plains of Texas and New Mexico: Environmental Science & Technology, v. 40, no. 10, pp. 3156-3162.

McMahon, P.B., and Böhlke, 2006, Regional patterns in the isotopic composition of natural and anthropogenic nitrate in ground water, High Plains, USA: Environmental Science & Technology, v. 40, no. 9, pp 2965 – 2970. 

McMahon, P.B., Dennehy, K.F., Bruce, B.W., Böhlke, J.K., Michel, R.L., Gurdak, J.J., and Hurlbut, D.A., 2006, Storage and transit time of chemicals in thick unsaturated zones under rangeland and irrigated cropland, High Plains, USA: Water Resources Research, 42, W03413, doi:10.1029/2005WR004417. 

Scanlon, B.R., R.C. Reedy, D.A. Stonestrom, D.E. Prudic, and K.F. Dennehy, 2005, Impact of land use and land cover change on groundwater recharge and quality in the southwestern US: Global Change Biology, v. 11, p. 1577-1593. 

McMahon, P.B., J.K. Böhlke, and S.C. Christenson, 2004, Geochemistry, radiocarbon ages, and paleorecharge conditions along a transect in the central High Plains aquifer, southwestern Kansas, USA : Applied Geochemistry, vol. 19(11), 1655-1686.| PDF

Walvoord, M. A., F. M. Phillips, D. A. Stonestrom, R. D. Evans, P. C. Hartsough, B. D. Newman, and R. G. Striegl, 2003, A reservoir of nitrate beneath desert soils: Science, v. 302, p. 1021-1024. 

Dennehy, K.F., Litke, D.W., and McMahon, P.B., 2002, The High Plains aquifer, USA: groundwater development and sustainability : In Hiscock, K.M., Rivett, M.O., and Davison, R.M. (eds.), Sustainable Groundwater Development, Geological Society, London, Special Publications, 193, p. 99-119.

Bruce, B.W. and Oelsner, G.P., 2001, Contrasting water quality from paired domestic/public supply wells, central High Plains: Journal of the American Water Resources Association, v. 37, No. 5, pp. 1389-1403.

McMahon, P.B., B.W. Bruce, M.F. Becker, L.M. Pope, and K.F. Dennehy, 2000, Occurrence of Nitrous Oxide in the Central High Plains Aquifer, 1999: Environmental Science & Technology, v. 34, pp. 4873-4875.| PDF

Gurdak, J.J., McMahon, P.B., Dennehy, K.F., and Qi, S.L., (2009), Water quality in the High Plains aquifer, Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming, 1999–2004: U.S. Geological Survey Circular 1337, 63 p.

Landon, M.K., Clark, B.R., McMahon, P.B. McGuire, V.L., and Turco, M.J., (2008), Hydrogeology, Chemical Characteristics, and Transport Processes in the Zone of Contribution of a Public-Supply Well in York, Nebraska: U.S. Geological Survey Scientific Investigations Report 2008-5050, 35 p.

McMahon, P.B., Dennehy, K.F., Bruce, B.W., Gurdak, J.J., and Qi, S.L., (2007), Water-quality assessment of the High Plains aquifer, 1999-2004: U.S. Geological Survery Professional Paper 1749, 136 p.

McMahon, P.B., J.K. Böhlke, and C.P. Carney, (2007), Vertical gradients in water chemistry and age in the northern High Plains aquifer, Nebraska, 2003: U.S. Geological Survery Scientific Investigations Report 2006-5294, 35 p.PDF

Stanton, J.S., and Qi, S.L., (2006), Ground-water quality of the northern High Plains aquifer, 1997, 2002–04: U.S. Geological Survey Scientific Investigations Report 2006-5138, 59 p.PDF

Stanton, J.S., and Fahlquist, Lynne, (2006), Ground-water quality beneath irrigated cropland of the northern and southern High Plains aquifer, Nebraska and Texas, 2003-04: U.S. Geological Survey Scientific Investigations Report 2006-5196, 39 p., appendixes on compact disk.PDF

Qi, S.L., and Gurdak, J.J., 2006, Percentage of probability of nonpoint-source nitrate contamination of recently recharged ground water in the High Plains aquifer: USGS Data Series DS-192(GIS dataset). 

Gurdak, J.J., and Qi, S.L., 2006, Vulnerability of Recently Recharged Ground Water in the High Plains Aquifer to Nitrate Contamination: USGS Scientific Investigations Report 2006-5050, 39 p.PDF