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High Plains Aquifer System

High Plains Aquifer System. Major rivers crossing the High Plains. Platte River. Arkansas River. Canadian River. Geologic History.

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High Plains Aquifer System

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  1. High Plains Aquifer System

  2. Major rivers crossing the High Plains Platte River Arkansas River Canadian River

  3. Geologic History • Deposition of basement rocks, Permian-Tertiary. Permian contains evaporites, affect water quality, cause subsidence. Late Cretaceous seds contains gypsum. Doming centered on OK/TX • Laramide uplift in early Tertiary, seaway in midwest. • Large braided river system transport sed to the east off Rocky Mtns, Miocene to Pliocene. Coarse grn, variable sorting. Sand and gravel up to 1000 ft thick. Ogallala frm

  4. Geologic History, Continued • Continued uplift tilts Ogallala frm. Removed by erosion near mountains, locally. • Dust storms deposit silt (loess) during Pleistocene, potential confining units • Eolian processes rework . Dunes formed. • Modern river systems rework. Alluvium formed

  5. Basement geology • Cretaceous SS contribute water • Marine basement rocks affect water quality, Cl, SO4

  6. Permian redbeds underlying HP in western KS

  7. Geologic units within the High Plains aquifer system • Alluvium • Dune sand • Ogallala Frm • Airkaree Frm • Brule Frm

  8. Stratigraphic section

  9. Fence diagram Regional dip

  10. Rule of Vs Dip of the lower contact relative to the gradient of dissecting rivers

  11. Escarpment from High Plains aquifer in eastern, CO

  12. Physiography of northern High Plains

  13. Outcrop of Ogallala frm

  14. Loess confining unit in NE

  15. GW/SW interaction variations in KS

  16. Gaining reach, channel cut through HP to bedrock Fence diagram Losing reach, channel underlain by HP Regional dip

  17. Hydraulic conductivityft/day

  18. Saturated thickness

  19. Basic Characteristics • Thick, unconfined aquifer. Locally confined by loess or caliche • K: 10 to 100 m/day; 30m/day average 30m/day = 3x10-4 m/s • b: 300 m max; 30 m average • T: 1000 m2/day • S: 0.1 to 0.3; 0.15 average (specific yield)

  20. Recharge Ave Magnitude: increases from 1 mm/yr in N.TX to 150 mm in dunes in NE • Infiltration on uplands • Losing streams; ephemeral streams with permeable beds (1.3% loss/mile in one study). Locally streams losing due to pumping • Irrigation return (irrigation-ET) • Bedrock (where upward flow occurs) Factors affecting distribution of recharge…

  21. How to estimate distributed recharge? One approach…. • Water balance on vadose zone Precipitation = ET + Interflow + Recharge Where interflow is small (low slope, far from drainage) Recharge = Precipitation – ET • Important factors Precipitation, Temp, Vegetation, Slope, K of surface materials

  22. Precipitation on High Plains

  23. Precipitation

  24. Potential ET Potential ET produced when rate is limited by energy input and plant metabolism, not limited by availability of water. Potential ET >Actual ET

  25. Precip and Pan Evaporation

  26. Mean lake evaporation Figure 3. Mean annual lake evaporation in the conterminous United States, 1946-55. Data not available for Alaska, Hawaii, and Puerto Rico. (Source: Data from U.S. Department of Commerce, 1968).

  27. Potential recharge in KS determined using soil model

  28. Playa lake on High Plains aq in TX panhandle20,000 playa lakes in TX

  29. Playas = important feature affecting recharge of High Plains aquifer • Focused recharge • Amount of recharge • Distribution • Water quality • Timing Uniformly distributed recharge

  30. Discharge • Streams; perennial, ephemeral • Seeps, springs • Riparian ET. May be significant where w.t. shallow (near surface water) • Wells

  31. What is the average horizontal hydraulic head gradient • What is the horizontal gw flux in the aquifer (m/d)? • What is the average gw velocity? (m/d) • Use the head contours to identify an area of suspected recharge. Circle the area, write “R” and draw gw flux vectors. List both geologic and meteorologic factors supporting your choice of recharge area • Identify an area of negligible recharge. List geologic or meteorologic factors supporting your choice of recharge area. Circle and write “NR” and draw gw flux vectors. • Identify a gaining stream reach. Circle and write “G” draw gw flux vectors • Identify a losing stream reach. Circle and write “L” and draw gw flux vectors

  32. = 40 miles Hydraulic gradient 400 ft/40 miles 10 ft/mile =1/500 = 0.002 Flux: 0.002* 30 m/d = 0.06 m/day Velocity = 0.06/0.2 = 0.3 m/d Hydraulic head contours in High Plains aquifer

  33. Gaining reach Losing reach Evidence for gw/sw interaction

  34. Diverging flow Possibly recharge here R Parallel flow, uniform gradient Recharge? Evidence for recharge

  35. Water Use • Pre-1930s: Irrigation from surface water. Dust Bowl Drought • 1930s Centrifugal well pump developed. • 1949: 2x106 acres mostly N TX. Platte R. • 1950s-60s: Drought. Oil and gas=energy source, more irrigation • 1960s: Centrifugal pump improved. 750 gpm well = central pivot irrigation, r=0.25 mi • 1978: 27000 central pivot systems, 13x106 acres • Pumping exceeds recharge by 100+x • Water levels drop 100 ft+. GW mining. Pumping costs increase

  36. Roughly 4 x106 acre ft/yr in KS Translate to flux to improve understanding KS, 150x200 miles=30000 mi2 639 acres=1mi2 19x106 acres Or 4/19=0.2 ft/yr Roughly 4 x106 acre ft/yr in KS Significance??

  37. Central pivot irrigation

  38. Number of central pivot irrigation systems in NE

  39. Aerial view of area using central-pivot irrigation

  40. Central pivot from the air

  41. Density of land being irrigated, 1949

  42. Density of land being irrigated1979

  43. Figure 5. Irrigated cropland 1992, Northern Plains region. USDA, NRCS, Lambert Conformal Conic Projection, 1927 North American Datum. Source: National Cartography and GIS Center, NRCS, USDA, Ft. Worth, TX, in cooperation with the natural Resources Inventory Division, NRCS, USDA, Washington, D.C., using GRASS/MAPGEN software, 09/95. Map based on data generated by NRI Division using 1992 NRI. Because the statistical variance in some of these areas may be large, the map reader should use this map to identify broad trends and avoid making highly localized interpretations Irrigated land, 1992

  44. Predevelopment to 1980 Aquifer sustainabilityWater balanceEco-impactChemistry Water balance on aquifer Recharge+Irrigation return = Baseflow + Pumping + Riparian ET + rate of change of storage

  45. Water storage in aquiferPredevelopment saturated thickness in KS

  46. Change in saturated thickness in KS

  47. Change of water in storage as percent of thickness

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