Fiber optic distributed temperature monitoring in mini-Anaheim spreading basin, Orange County, California

Artificial recharge basins are used to replenish aquifers and supply most of the drinking water for Orange County, California. The purpose of this thesis project is to test a method to measure spatial distribution of percolation rate in an aquifer recharge basin using heat as a tracer of water infiltration, Diurnal temperature gradients were measured along a basin transect using fiber-optic distributed temperature sensing (FODTS) with cables buried at two depths. Cross-correlation wavelet analysis was used to find the time phase shift (time lag) of diurnal temperature oscillations between the surface basin and two depths below the basin. The time lag data were used to estimate specific discharge (infiltration) across the basin. During periods of relatively constant infiltration rate, FODTS estimates agreed well with forward modeling using heat advection-dispersion theory (Stallman's Equation). The results indicate that the measurement of diurnal temperature propagation measured by FODTS can accurately measure the spatial distribution of infiltration rates, and has the potential to accurately estimate hydraulic conductivity.