HR: 0830h
AN: H11G-0939 [PDF]
TI: Simulation of the Effects of Climatic Extremes on Sources of Agricultural Drain Flow, Western San
Joaquin Valley, California
AU: * Brush, C F
EM: cfbrush@usgs.gov
AF: CSU Sacramento (contract employee with the US Geological Survey), 6000 J Street,
Placer Hall, Sacramento, CA 95819 United States
AU: Phillips, S P
EM: sphillip@usgs.gov
AF: US Geological Survey, 6000 J Street,
Placer Hall, Sacramento, CA 95819 United States
AU: Burow, K R
EM: krburow@usgs.gov
AF: US Geological Survey, 6000 J Street,
Placer Hall, Sacramento, CA 95819 United States
AU: Knifong, D L
EM: dknifong@usgs.gov
AF: US Geological Survey, 6000 J Street,
Placer Hall, Sacramento, CA 95819 United States
AU: Belitz, K
EM: kbelitz@usgs.gov
AF: US Geological Survey, 5735 Kearny Villa Road, Suite 0, San Diego, CA 92123 United States
AB:
Selenium loads in discharges from agricultural tile drains in the Grasslands area of the western San Joaquin Valley have
exceeded regulatory thresholds after heavy rainfalls in recent years. A three-dimensional numerical ground-water flow model
was developed to evaluate the effects of climatic extremes on the sources and quantities of tile drainage in the 100,000-acre
Grasslands area. The model simulates transient flow in the semiconfined and confined aquifers above and below the Corcoran
Clay Member of the Tulare Formation. Three-dimensional kriging of lithologic data from approximately 500 boreholes was used
to approximate the spatial distribution of sediment texture in the alluvial semiconfined aquifer in eight model layers.
Aquifer permeability of the semiconfined aquifer was then simulated as the weighted mean of assigned permeabilities of the
variable coarse- and fine-grained lithologic end members. The confining unit and confined aquifer were each represented by a
single model layer with constant permeability. Recharge and ground-water pumpage were estimated from available surface-water
delivery and crop-acreage data using a water-budget model. The ground-water flow model was calibrated using hydrologic data
for 1972-2000. The model is being used to evaluate causative agents that affect drain flows in the Grasslands area and to
identify flow paths and contributing areas for water collected by these drains.
DE: 1829 Groundwater hydrology
SC: Hydrology [H]
MN: 2003 Fall Meeting