Models of unsaturated flow and chloride transport under different agricultural settings were calibrated to deep vadose-zone samples or monitoring systems' data. The land settings include irrigated citrus orchards in light and heavy soils, a rain-fed winter crop field, an irrigated summer crop field and a bare sand dune. Vadose zone monitoring system (VMS), which enables continuous measurements of the vadose zone water content and frequent sampling of pore water at selected points across the entire vadose zone were used in three sites. In other sites direct push rigs were used for obtaining continuous core to depths ~ 10 m, and all physical and chemical characterization were derived in the lab. Hydrus 1D code was used for calibrating the models, validation runs (only in monitored sites) and simulations. In orchards, large variability of rechrge rates within the same orchard was observed. On average, relatively low recharge rates were calculated (~10% of precipitation+ irrigation), and high masses of chloride accumulations are found in many profiles obtained under orchards. Recharge variability within the same crop-field was usually smaller than the variability found in orchards while average relative recharge rates are usually higher than in orchards. Calibrated models were used for simulation of long periods and some simple precipitation-recharge statistics for the different land uses were obtained. Scenarios of land-use and climate change where used to produce estimates of the effects of these changes on recharge (e.g. 25% drop in rainfall will lead to ~50% drop in recharge under rain-fed crop).
|Geophysical Research Abstracts
|Published - 1 Dec 2011
- 1875 HYDROLOGY / Vadose zone