Vadose and groundwater interactive model to study the soil water flow in dry condition

Abstract EN

In order to estimate the efficiency of biological drainage in lowering groundwater levels, a numerical interactive link between the SWATR and FMAQ models is developed.

SWATR simulates water flow in the vadose zone, while FMAQ simulates the flow in groundwater.

In the vadose zone, one-dimensional vertical flow is assumed, while it is simulated as two-dimensional horizontal flow for the groundwater.

The main assumption of this interactive link is that the actual evapotranspiration is considered equal to the negative recharge rate from the groundwater table, which is the only excitation of the groundwater FMAQ model.

The effect of meteorological conditions, sink term description of plants and soil properties of vadose and groundwater zones are considered.

The water table fluctuation is the main output of the model.

For the climate, soil and plant characteristics considered, and to drain biologically a groundwater table at depth 100 cm below ground surface, the conducted sensitivity analysis shows that best root depth of a plant should be between 90 and 100 cm.

For the same water table in a clayey soil, plants of root depth of 60 cm do not need irrigation (under the studied conditions) since they are capable of extracting water from the groundwater for a period of 20 days.

For root depth of 90 cm with no precipitation, the overall actual transpiration increases with the increase of temperature or wind speed.

No change in overall actual transpiration was noticed until the value of precipitation reaches 5 mm/day.

After this value, the trend of increase is exponential although it is very small.

The overall transpiration after 28 days decreases in the following order: clay, silt, and finally sand.