help,help,about irrigation in the arid region!

I am a novice of feflow! I am making a simulation of the groundwater system of a arid region with irregation. Now,I am encountered some difficulties and I hope someone can do me a favor to answer the questions below.

1.my first question is Can Feflow describe the river and its interaction with the groundwater?

2. In my study region, the irrigation  often runs out of the water in the river at some place. I have the statistics of the flux at the upriver station and downriver station.The question is How can I get rid of the water used in irrigation from my river?
P.S.  my river is described by the discrete element in feflow

3.In the discrete element submenu, What exactly the following parameters stands for?
source/sink,roughness,cross area,transfer rate in/out.
and what do the Q and Qp mean in the fomula editor/user define!

thans for anyone's help!!

1. FEFLOW itself can describe the river as a boundary condition, e.g., a transfer condition. If full interaction between groundwater and surface water is needed, FEFLOW can be coupled to MIKE11 (see http://www.wasy.de/english/products/feflow/ifmmike11.html).
2. I would not use a discrete element for the river in FEFLOW. Discrete elements are automatically turned off above the groundwater table, which makes such an application difficult. If you need to run an integrated gw-sw system, you should use the coupling with MIKE 11 or a fully integrated system such as MIKE SHE.
3. Source/sink is a water source or sink in the discrete element. For roughness and cross sectional area, please see the corresponding white paper in the FEFLOW documentation. Transfer rate is used in case of a transfer boundary condition on the discrete element. Qp is the source/sink term that is calculated by the equation the formula editor, Q is the defined source/sink parameter for the discrete element. By default Qp=Q, therefore no specific equation is used for the source/sink calculation.

thanks a lot