Modeling the spatial and temporal dynamics of infiltration during managed aquifer recharge
Abstract
We create a series of 1D models to explain the temporal and spatial dynamics of infiltration through shallow soils during managed aquifer recharge (MAR). We use a variety of techniques, tools, and analytical methods to assess both controls on infiltration rates and impacts on water supply and water quality in the underlying aquifer. We obtain field data from a 3 ha recharge pond operating in central coastal California. At multiple locations beneath the MAR pond, nested instruments continuously record subsurface temperature, soil moisture and pressure at depths ranging from 5 to 150 cm below the water-sediment interface. Temperature records are used to derive infiltration rates at individual locations, and water content sensors help to determine saturation profiles with depth. Infiltration rates are combined with pressure records to assess changes to saturated soil hydraulic conductivity with time. Repeated surveys of soil texture resolve spatial and temporal differences in the fraction of fine grained material at depth, as well as the formation of a crust at the soil surface. We document considerable variability in infiltration rates over the course of MAR operating season. In certain areas, initial infiltration rates exceeding 5 m d-1 decrease abruptly to <0.1 m d-1 after the first few weeks of MAR operation. Conversely, infiltration rates in areas that are virtually stagnant at the onset of operation increase to >0.5 m d-1 after several months. Large changes in infiltration rate are associated with order of magnitude changes in the saturated hydraulic conductivity of shallow soils below the pond. We have developed a series of variable saturation models in an attempt to replicate this behavior, taking into account the deposition and penetration of fine grained sediments during MAR.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.H41E1077R
- Keywords:
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- 1830 HYDROLOGY / Groundwater/surface water interaction;
- 1838 HYDROLOGY / Infiltration;
- 1847 HYDROLOGY / Modeling