Unsaturated-Zone Study - central High Plains

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Special drill rig used for drilling the unsaturated-zone study wells. The drill rig is a casing-advance type that brings cuttings to the surface using air rather than fluid.

Instrumentation for monitoring the unsaturated zone in the central High Plains

Detail of surface-installation at the unsaturated-zone study sites

Gas sampling in the mobile water-quality lab

Objective:
• Measure recharge rates and chemical fluxes to the water table through relatively thick unsaturated sediments under irrigated and non-irrigated conditions.
  
Approach:
• Instrument 3 sites (2 irrigated, 1 non-irrigated) with depth to water about 200 feet (see map). Collect borehole cuttings and core for analysis. Place a well, suction lysimeters, heat-dissipation probes, and gas sampling ports in each borehole. Determine recharge rates using multiple techniques (Darcian flow, Chloride mass-balance, Tritium profiles, Temperature profiles, Chemical tracers). Use calculated recharge rates with soil-water chemistry to determine chemical fluxes.
  
Timing:
• Drilling begins March, 2000

Targeted Constituents:
• Sediment
  Physical properties:
  Grain size, porosity, bulk density, water content, soil moisture retention, saturated K, and unsaturated K.
  Chemistry:
  Soil pH, organic carbon, selected nutrients, selected major ions, stable isotopes, selected pesticides, and tritium.
• Ground Water Chemistry:
  Physical properties, nutrients, major ions, DOC, trace elements, pesticides, tritium, and stable isotopes.
  

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maintained by: slqi@usgs.gov
URL: http://co.water.usgs.gov/nawqa/hpgw/activities/UNSAT1.html