Unsaturated Zone Study - northern High Plains (cont.)
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:
Boreholes drilled and instruments installed June-July, 2002.
2003 UPDATE: Sampling done September, 2002, April, 2003, May,
2003, and August, 2003
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.
