Many of the hydrological and ecological functions of alluvial ﬂood plains within watersheds depend on the water ﬂow exchanges between the vadoze soil zone and the shallow groundwater. The water balance of the soil in the ﬂood plain is investigated, in order to evaluate the main hydrological processes that underlie the temporal dynamics of soil moisture and groundwater levels. The soil moisture and the groundwater level in the ﬂood plain were monitored continuously for a three-year period. These data were integrated with the results derived from applying a physically-based numerical model which simulated the variably-saturated vertical water ﬂow in the soil. The analysis indicated that the simultaneous processes of lateral groundwater ﬂow and the vertical recharge from the unsaturated zone caused the observed water table ﬂuctuations. The importance of these ﬂows in determining the rises in the water table varied, depending on soil moisture and roundwater depth before precipitation. The monitoring period included two hydrological years (September 2009–September 2011). About 13% of the precipitation vertically recharged the groundwater in the ﬁrst year and about 50% in the second. The difference in the two recharge coefﬁcients was in part due to the lower groundwater levels in the recharge season of the ﬁrst hydrological year, compared to those observed in the second. In the latter year, the shallow groundwater increased the soil moisture in the unsaturated zone due to capillary rise, and so the mean hydraulic conductivity of the unsaturated soil was high. This moisture state of soil favoured a more efﬁcient conversion of inﬁltrated precipitation into vertical groundwater recharge. The results show that groundwater dynamics in the ﬂood plain are an important source of temporal variability in soil moisture and vertical recharge processes, and this variability must be properly taken into account when the water balance is investigated in shallow groundwater environments.
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|Titolo:||EVALUATION OF THE SOIL WATER BALANCE IN AN ALLUVIAL FLOODPLAIN WITH A SHALLOW GROUNDWATER TABLE|
|Data di pubblicazione:||2013|
|Appare nelle tipologie:||1.1 Articolo in rivista|