NS44A-02
Controls on infiltration due to spatial heterogeneity in a small recharge basin observed using time-lapse distributed temperature sensing
Thursday, 17 December 2015: 16:20
3024 (Moscone West)
Andrew Parsekian, University of Wyoming, Laramie, WY, United States, Chloe M Mawer, Stanford University, Los Altos Hills, CA, United States, Adam Pidlisecky, University of Calgary, Calgary, AB, Canada and Rosemary J Knight, Stanford University, Stanford, CA, United States
Abstract:
Managed aquifer recharge (MAR) depends on sufficient infiltration capacity within the near-surface sediments to pass water from a retention pond into the subsurface for storage. MAR system operations may be optimized with a detailed understanding of pond-bottom infiltration properties. We used two vertically co-located fiber optic distributed temperature sensing (FO-DTS) cables in a 0.63 hectare basin to observe a phase shift due to the diurnal temperature signal for estimating infiltration rate at high spatial and temporal resolution. While the average infiltration rate remains relatively constant under fixed-head conditions, the maximum infiltration rate varies more than an order of magnitude even over daily timescales. On average, half of the pond bottom infiltrated nearly 80% of the total water volume during the course of the experiment. We also found spatial variability in the rate of change of infiltration rate during a 5-day ponding cycle, an effect we attribute to variable biological pore clogging. Areas with high initial infiltration rate experienced pore clogging and subsequent decrease in infiltration efficiency. These results suggest that sparse, discrete estimates of infiltration would be insufficient to effectively understand how the near-surface properties control movement of water from the pond into the subsurface.
