Water Movement Through the Unsaturated Zone of the High Plains Aquifer in the Central Platte Natural Resources District, Nebraska
Eight unsaturated-zone research sites were installed in the Central Platte Natural Resources District as part of the High Plains Unsaturated-Zone Research Network. These 8 sites were installed to determine recharge and chemical transport rates in the unsaturated zone beneath important land-use settings and climate gradients across the Central Platte Natural Resources District.
The 8 research sites are included in the Central Platte NRD Unsaturated-Zone Network (UZN). The UZN is designed to answer questions about recharge in the Central Platte region including
- How does recharge vary with the climate gradients across the Central Platte NRD?
- How does recharge vary under important land-use settings?
STUDY DESIGN
To answer questions about recharge in the Central Platte region, we are
- Measuring water (recharge) fluxes and chemical storage in the unsaturated zone.
- Estimating chemical transit times from land surface to the water table.
SITES
- Five in the eastern part of the NRD (3 in Hall County and 2 in Buffalo County)
- Three in the western part of the NRD (3 in Dawson County)
- Depth to groundwater exceeded 10 meters at seven sites.
- Sites located in a variety of land uses: rangeland, irrigated corn, dryland corn, pastureland, irrigated alfalfa, upland rangeland.
Available Data:
Data for this study are stored in the USGS National Water Information System (NWISweb). Links to data below are listed by USGS site identification.
- Site 1 (Hall County, rangeland): 410102098374201
- Site 2 (Hall County, irrigated corn): 405855098383001
- Site 3 (Buffalo County, dryland corn) : 405503098441801
- Site 4 (Buffalo County, pastureland): 405435098432601
- Site 5 (Hall County, irrigated corn): 405040098384503
- Site 6 (Dawson County, irrigated corn): 405855100073901
- Site 7 (Dawson County, irrigated alfalfa): 405118099514901
- Site 8 (Dawson County, upland rangeland): 405738099504501
Each site contains a weather station and an instrumented borehole and 2 to 4 monitoring wells. Instruments used at the sites include
- heat dissipation probes
- suction lysimeters
Wells were installed just below the water table to determine the chemical and isotopic composition of the most recently recharged groundwater. Groundwater samples are collected and analyzed for
- Major ions and nutrients: calcium, magnesium, sulfate, nitrate.
- Environmental tracers: chlorofluorocarbons, sulfur hexafluoride, tritium, and tritium/helium.
- Field parameters: pH, temperature, specific conductance, dissolved oxygen, and alkalinity.
Environmental tracers are used for determining groundwater age. Analysis of environmental tracers in shallow groundwater indicate most residence times greater than 50 years at sites outside the Platte River Valley, and less than 10 years at sites within the Platte River Valley. Continuous soil cores were analyzed for particle size, bulk density, and pore-water concentrations of nitrate (NO3–) as N, chloride (Cl–), and tritium (3H). Peaks of pore-water 3H concentrations in soil profiles from the atmospheric nuclear bomb testing in the 1960s could not be determined at some locations probably because of 3H being flushed through the unsaturated zone since the nuclear bomb tests. Using available 3H peak profiles, recharge rates of about 58 mm/yr were computed, which is consistent with other studies in the High Plains aquifer. Pore-water NO3– and Cl– concentrations in soil cores indicated peaks similar in shape and depth to the 3H profiles. Preliminary data indicate that water and chemical fluxes in the unsaturated zone are a function of irrigation patterns, regional precipitation gradient, and winter precipitation events.
- Overview
Eight unsaturated-zone research sites were installed in the Central Platte Natural Resources District as part of the High Plains Unsaturated-Zone Research Network. These 8 sites were installed to determine recharge and chemical transport rates in the unsaturated zone beneath important land-use settings and climate gradients across the Central Platte Natural Resources District.
Sources/Usage: Some content may have restrictions. View Media DetailsMap of the unsaturated zone network sites in the Central Platte river basin, NE. The 8 research sites are included in the Central Platte NRD Unsaturated-Zone Network (UZN). The UZN is designed to answer questions about recharge in the Central Platte region including
- How does recharge vary with the climate gradients across the Central Platte NRD?
- How does recharge vary under important land-use settings?
STUDY DESIGN
To answer questions about recharge in the Central Platte region, we are
- Measuring water (recharge) fluxes and chemical storage in the unsaturated zone.
- Estimating chemical transit times from land surface to the water table.
SITES
Sources/Usage: Some content may have restrictions. View Media DetailsUSGS scientist sampling groundwater at recharge site 6 (Public domain.) - Five in the eastern part of the NRD (3 in Hall County and 2 in Buffalo County)
- Three in the western part of the NRD (3 in Dawson County)
- Depth to groundwater exceeded 10 meters at seven sites.
- Sites located in a variety of land uses: rangeland, irrigated corn, dryland corn, pastureland, irrigated alfalfa, upland rangeland.
Available Data:
Data for this study are stored in the USGS National Water Information System (NWISweb). Links to data below are listed by USGS site identification.
- Site 1 (Hall County, rangeland): 410102098374201
- Site 2 (Hall County, irrigated corn): 405855098383001
- Site 3 (Buffalo County, dryland corn) : 405503098441801
- Site 4 (Buffalo County, pastureland): 405435098432601
- Site 5 (Hall County, irrigated corn): 405040098384503
- Site 6 (Dawson County, irrigated corn): 405855100073901
- Site 7 (Dawson County, irrigated alfalfa): 405118099514901
- Site 8 (Dawson County, upland rangeland): 405738099504501
Sources/Usage: Some content may have restrictions. View Media DetailsGroundwater sampling at recharge site 5(Public domain.) Each site contains a weather station and an instrumented borehole and 2 to 4 monitoring wells. Instruments used at the sites include
- heat dissipation probes
- suction lysimeters
Wells were installed just below the water table to determine the chemical and isotopic composition of the most recently recharged groundwater. Groundwater samples are collected and analyzed for
- Major ions and nutrients: calcium, magnesium, sulfate, nitrate.
- Environmental tracers: chlorofluorocarbons, sulfur hexafluoride, tritium, and tritium/helium.
- Field parameters: pH, temperature, specific conductance, dissolved oxygen, and alkalinity.
Environmental tracers are used for determining groundwater age. Analysis of environmental tracers in shallow groundwater indicate most residence times greater than 50 years at sites outside the Platte River Valley, and less than 10 years at sites within the Platte River Valley. Continuous soil cores were analyzed for particle size, bulk density, and pore-water concentrations of nitrate (NO3–) as N, chloride (Cl–), and tritium (3H). Peaks of pore-water 3H concentrations in soil profiles from the atmospheric nuclear bomb testing in the 1960s could not be determined at some locations probably because of 3H being flushed through the unsaturated zone since the nuclear bomb tests. Using available 3H peak profiles, recharge rates of about 58 mm/yr were computed, which is consistent with other studies in the High Plains aquifer. Pore-water NO3– and Cl– concentrations in soil cores indicated peaks similar in shape and depth to the 3H profiles. Preliminary data indicate that water and chemical fluxes in the unsaturated zone are a function of irrigation patterns, regional precipitation gradient, and winter precipitation events.
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